Construction method of outer shell lining for large cross-section tunnel

Abstract

To provide a method of constructing an outer shell lining of a large cross-section tunnel, which is constructed by interconnecting a group of small cross-section shields, with superior workability compared to conventional methods.SOLUTION: The present invention comprises an outer shell shield constructing step in which a plurality of small cross-section shields are connected to each other in a bead-like manner to form an annular outer shell shield, and an outer shell ring frame constructing step which forms an outer shell ring frame including an annular steel main girder ring extending in the circumferential direction of the outer shell shield and frame concrete. The steel main girder ring includes many main girder steel plates that are mutually jointed via perforated steel plate dowels rigidly joined at both ends in the longitudinal direction. In the outer shell ring frame constructing step, concrete is poured while the perforated steel plate dowels placed at the ends of the main girder steel plates to be mutually joined are placed oppositely to and spaced from each other, and the main girder steel plates are joined to each other through the concrete.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for constructing an outer shell lining for a large cross-section tunnel. [Background technology]

[0002] Conventionally, a method for constructing a large-section underground structure underground involves surrounding the natural ground with multiple small-section tunnels to form the outer shell of a large-section tunnel, and then excavating the natural ground inside (see, for example, Patent Document 1).

[0003] For example, Patent Document 1 discloses a construction method for an underground widening section, which includes a construction step of a starting base for constructing a starting base of a shield machine for removing a segment of a shield tunnel and constructing an underground widening section in a circular shape around the shield tunnel, a construction step of a leading shield for constructing a plurality of leading shields with cuttable segments arranged therein by starting a leading shield machine from the starting base and constructing a plurality of trailing shields in a ring shape at intervals, a construction step of a trailing shield for constructing a plurality of trailing shields in a ring shape while cutting a part of the leading shield by starting a trailing shield machine from the starting base, a construction step of an outer shell shield for connecting the leading shield and the adjacent trailing shield to form the outer shell of the underground widening section, and an excavation step for excavating the inside of the outer shell shield after the construction of the outer shell shield. Patent Document 1 also discloses that an outer shell lining is constructed by an RC ring lining having reinforcing bars and concrete inside the leading shield and the trailing shield. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-094818 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, when constructing the outer shell lining of a large cross-section tunnel by connecting small cross-section shields such as leading and trailing shields, if the outer shell lining is constructed with an RC ring lining, it is necessary to carry out reinforcing work in a narrow space surrounded by the segments of each small cross-section shield (leading and trailing shield), and there is room for improvement in workability. In response to this, one proposal is to construct the outer shell lining with a steel concrete framework instead of an RC ring lining. However, if the main girders extending along the circumferential direction of the outer shell shield are to be joined together by welding, if there is a construction error in the construction position of each small cross-section shield constructed underground, it is difficult to absorb the construction error, and it is also assumed that it may be difficult to efficiently join the main girders together.

[0006] The present invention has been made in consideration of the above-mentioned situation, and its object is to provide a method for constructing an outer shell lining for a large cross-section tunnel, which is constructed by interconnecting a group of small cross-section shields, and which has better workability than conventional methods. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a construction method for an outer shell lining for a large cross-section tunnel, comprising: an outer shell construction step of forming a ring-shaped outer shell shield tunnel by connecting together segments of a plurality of small cross-section shield tunnels arranged in parallel underground in a rosary-like manner; and an outer shell ring structure construction step of forming an outer shell ring structure inside the outer shell shield tunnel, the outer shell ring structure including an annular steel main girder ring extending along the circumferential direction of the outer shell shield tunnel and structure concrete covering the steel main girder ring, the steel main girder ring being a longitudinal axial length of the outer shell shield tunnel. The outer shell ring structure construction process includes a plurality of main girder steel plates that are jointed to each other via perforated steel plate dowels rigidly joined to both ends in the longitudinal direction, and concrete is poured into the outer shell shield tunnel so that the perforated steel plate dowels arranged at the ends of the main girder steel plates to be joined to each other are arranged facing each other with a gap between them, and the perforated steel plate dowels are embedded in the concrete, and the main girder steel plates are joined to each other via the concrete.

[0008] In the outer shell ring body construction process, a leading shield machine may be launched from a launch base constructed underground, and multiple leading shield tunnels in which cuttable segments are arranged at intervals from each other may be constructed, and then a trailing shield machine may be launched from the launch base, and multiple trailing shield tunnels may be constructed while cutting portions of the leading shield tunnels between adjacent leading shield tunnels, thereby connecting the alternating leading shield tunnels and the trailing shield tunnels in a rosary-like manner, and the outer shell shield tunnel may be formed by cutting open the segments of the trailing shield tunnels located at the boundary between them and the leading shield tunnels.

[0009] In addition, the steel main girder ring includes a leading side main girder steel plate that is horizontally laid within the leading shield tunnel so as to extend along the circumferential direction of the outer shell shield tunnel, and a trailing side main girder steel plate that is horizontally laid within the trailing shield tunnel so as to extend along the circumferential direction of the outer shell shield tunnel, and in the outer shell ring body construction process, a leading side perforated steel plate dowel, which is a perforated steel plate dowel arranged at the end of the leading side main girder steel plate, and a trailing side perforated steel plate dowel, which is a perforated steel plate dowel arranged at the end of the trailing side main girder steel plate, may be joined together via concrete.

[0010] Furthermore, in the outer shell ring body construction process, before constructing the trailing shield tunnel, a leading outer shell body portion which becomes part of the outer shell ring body may be constructed in advance in a predetermined outer shell body construction area within the leading shield tunnel which does not include a cutting area to be cut by the trailing shield machine, and when constructing the leading outer shell body portion, a box cut-out portion for box-cutting concrete may be formed in an end area including the leading side perforated steel plate dowel in the leading side main girder steel plate, and after constructing the trailing shield tunnel, the trailing side perforated steel plate dowel in the trailing side main girder steel plate is inserted into the box cut-out portion, and concrete is filled in the trailing shield tunnel and in the box cut-out portion, thereby joining the ends of the leading side main girder steel plate and the trailing side main girder steel plate together and constructing a trailing outer shell body portion which becomes part of the ring body in the trailing shield tunnel.

[0011] In addition, in the outer shell ring body construction process, concrete may be poured into the outer shell shield tunnel with a rod-shaped or plate-shaped reinforcing iron material inserted so as to straddle the dowel hole of one perforated steel plate dowel arranged opposite to each other and the dowel hole of the other perforated steel plate dowel.

[0012] In addition, in the outer shell ring body constructing step, the leading side perforated steel sheet dowel and the trailing side perforated steel sheet dowel may be arranged opposite each other with a gap therebetween in the up-down direction.

[0013] In addition, in the outer shell ring body construction process, the leading side main girder steel plate and the trailing side main girder steel plate may be joined in a state where their end regions are attached to each other.

[0014] In addition, in the outer shell ring body construction process, the leading side main girder steel plate and the trailing side main girder steel plate may be arranged opposite each other with a horizontal gap, and the leading side perforated steel plate dowel and the trailing side perforated steel plate dowel may be arranged opposite each other with a horizontal gap.

[0015] In addition, end plates are rigidly joined to the end faces of the leading side main girder steel plate and the trailing side main girder steel plate. This is also fine.

[0016] In addition, a restraining steel plate for restraining concrete may be provided at the joint portion of the leading side main girder steel plate and the trailing side main girder steel plate so as to cover the upper and lower parts of the leading side perforated steel plate dowel and the trailing side perforated steel plate dowel. Effect of the Invention

[0017] According to the present invention, a method for constructing an outer shell lining for a large cross-section tunnel, which is constructed by interconnecting a group of small cross-section shields, can be provided which is easier to work than conventional methods. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating an underground widening section constructed using the construction method for an outer shell covering body according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram of the underground widening section according to the first embodiment, viewed from the single side of the main line toward the branching and merging section side. [Diagram 3] FIG. 3 is a diagram showing a construction procedure of the underground widening portion according to the first embodiment. [Figure 4] FIG. 4 shows the constructed starting shaft. [Diagram 5] FIG. 5 shows the constructed circumferential shield. [Figure 6] FIG. 6 is a diagram showing frozen soil formed so as to cover the front and rear end faces of the circumferential shield. [Figure 7] FIG. 7 is a diagram showing the constructed launch base. [Figure 8] FIG. 8 is a diagram for explaining the construction of a leading shield. [Figure 9] FIG. 9 is a diagram showing a schematic diagram of a state in which construction of a predetermined number of preliminary shields has been completed. [Figure 10] FIG. 10 is a diagram illustrating a cross section of the leading shield. [Figure 11] FIG. 11 is a diagram showing a state in which a freezing tube is installed along the axial direction of the leading shield. [Figure 12] FIG. 12 is a diagram illustrating the leading shell body, cutting elements, and non-structural elements constructed within the leading shield. [Figure 13] FIG. 13 is a plan view of the leading inner peripheral steel shell element. [Figure 14] FIG. 14 is a front view of the leading inner peripheral side steel shell element. [Figure 15] FIG. 15 is a side view of the leading inner peripheral steel shell element. [Figure 16] FIG. 16 is a plan view of the leading outer circumferential steel shell element. [Figure 17] FIG. 17 is a front view of the leading outer peripheral steel shell element. [Figure 18] FIG. 18 is a side view of the leading outer peripheral steel shell element. [Figure 19] FIG. 19 is a diagram showing the leading inner peripheral side steel shell element and the leading outer peripheral side steel shell element positioned and fixed to the leading shield. [Figure 20] FIG. 20 is a diagram showing a schematic arrangement state of leading inner peripheral side steel shell elements (leading outer peripheral side steel shell elements) arranged in series along the axial direction of the leading shield. [Figure 21] FIG. 21 shows a situation where non-structural elements are constructed in the outer region of the shell of the leading shield. [Figure 22] FIG. 22 is a diagram showing a state in which a leading outer shell body part has been constructed in the outer shell body construction area of ​​the leading shield. [Figure 23] FIG. 23 is a diagram for explaining the construction status of the trailing shield. [Figure 24] FIG. 24 is a diagram showing a cross section of the trailing shield. [Diagram 25] FIG. 25 is a diagram showing a schematic diagram of a state in which construction of a predetermined number of trailing shields has been completed. [Figure 26] FIG. 26 is a diagram showing a state in which a freezing pipe is installed along the axial direction of the trailing shield. [Figure 27] FIG. 27 shows the situation in which frozen soil has been created on the outer and inner sides of the outer shell shield. [Figure 28]FIG. 28 is a diagram illustrating the trailing shell body and non-structural elements constructed on the trailing shield. [Figure 29] FIG. 29 is a plan view of the trailing inner periphery steel shell element. [Diagram 30] FIG. 30 is a front view of the first steel shell unit in the trailing inner periphery side steel shell element. [Diagram 31] FIG. 31 is a side view of the first steel shell unit in the trailing inner periphery side steel shell element. [Diagram 32] FIG. 32 is a side view of the first steel shell unit in the trailing inner periphery side steel shell element. [Diagram 33] FIG. 33 is a front view of the trailing-side second main girder steel plate. [Diagram 34] FIG. 34 is a side view of the trailing-side second main girder steel plate. [Diagram 35] FIG. 35 is a plan view of the trailing outer peripheral steel shell element. [Diagram 36] FIG. 36 is a front view of the second steel shell unit 94B in the trailing outer periphery side steel shell element. [Figure 37] FIG. 37 is a side view of the second steel shell unit 94B in the trailing outer periphery steel shell element. [Figure 38] FIG. 38 is a side view of the second steel shell unit 94B in the trailing outer periphery side steel shell element. [Figure 39] FIG. 39 is a diagram for explaining the installation state of the trailing inner periphery side steel shell element. [Diagram 40] FIG. 40 is a diagram for explaining the installation state of the trailing inner periphery side steel shell element. [Diagram 41] FIG. 41 is a diagram for explaining the installation state of the trailing inner periphery side steel shell element. [Diagram 42] FIG. 42 is a diagram for explaining the installation state of the trailing inner periphery side steel shell element. [Diagram 43] FIG. 43 is a diagram for explaining the installation state of the trailing inner periphery side steel shell element. [Diagram 44] FIG. 44 is a diagram for explaining the installation state of the trailing inner periphery side steel shell element. [Diagram 45] FIG. 45 is a diagram for explaining the installation state of the trailing inner periphery side steel shell element. [Diagram 46] FIG. 46 is a diagram for explaining the installation state of the trailing outer peripheral steel shell elements. [Figure 47] FIG. 47 is a diagram for explaining the installation state of the trailing outer peripheral steel shell elements. [Figure 48] FIG. 48 is a diagram for explaining the installation state of the trailing outer peripheral steel shell elements. [Figure 49] FIG. 49 is a diagram for explaining the installation state of the trailing outer peripheral steel shell elements. [Figure 50] FIG. 50 is a diagram for explaining the installation state of the trailing outer peripheral steel shell elements. [Figure 51] FIG. 51 is a diagram showing a state in which a trailing inner periphery side steel shell element and a trailing outer periphery side steel shell element are installed on the trailing shield. [Figure 52] FIG. 52 shows the construction of non-structural elements in the outer region of the outer shell of the trailing shield. [Figure 53] FIG. 53 is a diagram showing a state in which the trailing shell body part has been constructed in the trailing shield shell body construction area. [Figure 54] Figure 54 is a diagram explaining the joining state between the trailing first perforated steel plate dowel in the trailing first main girder steel plate of the trailing inner circumference side steel shell element 93A and the leading side perforated steel plate dowel in the leading side main girder steel plate of the leading inner circumference side steel shell element in the dowel joint region. [Figure 55] Figure 55 is a diagram explaining the joining state between the trailing-side second perforated steel plate dowel in the trailing-side first main girder steel plate of the trailing inner circumference steel shell element and the trailing-side second perforated steel plate dowel in the trailing-side second main girder steel plate of the trailing inner circumference steel shell element in the dowel joint region. [Figure 56] FIG. 56 is a diagram showing an annular outer shell ring body formed within the outer shell shield. [Figure 57] Figure 57 shows the situation where frozen soil has been created at the bottom of the outer shell shield. [Figure 58] FIG. 58 shows the excavation situation inside the outer shell shield. [Figure 59] FIG. 59 is a diagram for explaining the first modification of the first embodiment. [Figure 60] FIG. 60 is a diagram for explaining the second modification of the first embodiment. [Figure 61] FIG. 61 is a diagram showing a modified example of the restraining steel plate. [Figure 62] FIG. 62 is a diagram showing an outer shell ring body of the outer shell shield according to the second embodiment. [Figure 63] FIG. 63 is a diagram showing a part of an outer shell ring body according to the second embodiment. [Figure 64] FIG. 64 is a view for explaining a connection relationship between a leading inner periphery side steel shell element and a trailing inner periphery side steel shell element according to the second embodiment. [Figure 65] FIG. 65 is a view for explaining a connection relationship between a leading outer periphery side steel shell element and a trailing outer periphery side steel shell element according to the second embodiment. [Figure 66] FIG. 66 is a view for explaining the leading inner circumference side steel shell element according to the second embodiment. [Figure 67] FIG. 67 is a partial enlarged view showing an end region of the leading inner peripheral side steel shell element according to the second embodiment. [Figure 68] FIG. 68 is a diagram for explaining the trailing first steel-shell unit 94C of the trailing inner circumference side steel-shell element according to the second embodiment. [Figure 69] FIG. 69 is a diagram for explaining the trailing second steel shell unit of the trailing inner circumference side steel shell element according to the second embodiment. [Figure 70] FIG. 70 is a view for explaining a leading outer peripheral steel shell element according to the second embodiment. [Figure 71] FIG. 71 is a diagram for explaining the trailing first steel shell unit of the trailing outer periphery side steel shell element according to the second embodiment. [Figure 72] FIG. 72 is a diagram for explaining the trailing second steel shell unit of the trailing outer periphery side steel shell element according to the second embodiment. [Figure 73] FIG. 73 is a view for explaining a state in which the leading inner periphery side steel shell elements according to the second embodiment are consecutively provided. [Figure 74]FIG. 74 is a diagram illustrating a splice plate according to the second embodiment. [Figure 75] FIG. 75 is a diagram showing a state in which the trailing perforated steel plate dowels of the trailing first steel shell unit and the trailing second steel shell unit are inserted into the dowel joint region of the leading inner circumference side steel shell element in embodiment 2, and positioning is completed. [Figure 76] FIG. 76 is a diagram for explaining the arrangement relationship between a leading-side perforated steel plate dowel of a leading-side main girder steel plate and a trailing-side perforated steel plate dowel of a trailing-side main girder steel plate according to the second embodiment. [Figure 77] FIG. 77 is a cross-sectional view taken along line VV of FIG. [Figure 78] FIG. 78 is a diagram showing the dowel joint region and its surroundings after concrete is poured in the second embodiment. [Figure 79] FIG. 79 is a diagram showing a shear reinforcement steel material according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Next, an embodiment of the present invention will be described with reference to the drawings. In the following embodiment, as an example of a large cross-section tunnel according to the present invention, a case where an underground widening section 1 where a main line shield tunnel (hereinafter simply referred to as "main line shield") 2 and a ramp shield tunnel (hereinafter simply referred to as "ramp shield") 3 branch off and join together will be described. However, the embodiment described below is an example for carrying out the present invention, and the present invention is not limited to the aspects described below.

[0020] <Embodiment 1> <Overall composition> FIG. 1 is a schematic diagram of an underground widening section 1 constructed using a construction method for an outer shell lining body according to embodiment 1. The underground widening section 1 is an example of a large-section tunnel with a branching and merging section formed inside where a main line shield 2 and a lamp shield 3 connect (branch and merge), and the internal cross section of the tunnel is wider than other parts. FIG. 2 is a schematic diagram of the underground widening section 1 according to embodiment 1, viewed from the single side of the main line (main line shield 2) (the side of arrow A in FIG. 1) toward the branching and merging section. Note that in this embodiment, the extension direction of the underground widening section 1 is referred to as the "tunnel axis direction." He said.

[0021] The underground widening section 1 includes, as its outer shell, an outer shell shield tunnel (hereinafter simply referred to as "outer shell shield") 4 and a roughly cylindrical outer shell lining body 10 including an outer shell ring body 9 constructed inside the outer shell shield 4. The outer shell shield 4 is a shield tunnel having a ring-shaped cross section perpendicular to its extension direction and a roughly cylindrical shape as a whole.

[0022] The outer shell shield 4 extends from a starting base 7 formed on the branching and merging section side (the far side in FIG. 1) where the main line shield 2 and the lamp shield 3 branch and merge toward the single side of the main line (main line shield 2) (the near side in FIG. 1). The outer shell shield 4 is formed in an annular (ring-shaped) shape by connecting a plurality of small cross-section shield tunnels together in a rosary shape. The plurality of small cross-section shield tunnels in this embodiment include a plurality of leading shield tunnels (hereinafter simply referred to as "leading shields") 5 and a plurality of trailing shield tunnels (hereinafter simply referred to as "trailing shields") 6, and the leading shields 5 and the trailing shields 6 are alternately connected in a rosary shape to form the outer shell shield 4 that is generally cylindrical as a whole. The number of leading shields 5 and trailing shields 6 that form the outer shell shield 4 is not particularly limited.

[0023] The outer shell ring body 9 formed inside the segment of the outer shell shield 4 is a structure including an annular steel main girder ring extending along the circumferential direction of the outer shell shield 4 and concrete covering the steel main girder ring. The details of the outer shell ring body 9 will be described later.

[0024] As shown in Fig. 2, on the inner space side surrounded by the outer shell lining structure 10 (outer shell shield 4), a deck 81 having a paved surface that forms the running path of vehicles, an internal structure 82 that supports the deck 81, etc. are constructed. Fireproof panels 83, etc. are installed on the inner surface of the outer shell lining structure 10 (outer shell shield 4). The arrival point side on the opposite side to the starting base 7 in the underground widening section 1 is connected to the main line shield 2.

[0025] <Construction method> Next, a description will be given of a construction procedure of the underground widening portion 1 according to embodiment 1. Fig. 3 is a diagram showing a construction procedure of the underground widening portion 1 according to embodiment 1. In steps S01 to S03, a launch base 7 for the shield machine is constructed.

[0026] First, in step S01, as shown in FIG. 4, the ground surface is excavated to install a starting shaft 11 to a predetermined depth. The starting shaft 11 is, for example, a caisson shaft. The starting shaft 11 is constructed by excavating the ground surface located above the position where the starting base 7 is to be constructed. In the example shown in FIG. 4, the starting shaft 11 is constructed at a position corresponding to the tip of the lamp shield 3 installed in the ground alongside the main line shield 2, and extends to a depth near the tip of the lamp shield 3. However, the starting shaft 11 is not limited to the caisson method and may be constructed by other construction methods.

[0027] Next, in step S02, as shown in FIG. 5, a closed-type circumferential shield machine (not shown) is launched from the bottom of the starting shaft 11 to construct the circumferential shield 12. Here, a part of the bottom side of the starting shaft 11 can be cut by the circumferential shield machine, and the circumferential shield 12 can be constructed while cutting a part of the starting shaft 11 by the circumferential shield machine. As shown in FIG. 5, the circumferential shield 12 is constructed in an annular (donut-shaped) shape starting from the bottom of the starting shaft 11 so as to surround the main line shield 2 and the lamp shield 3. Note that, before constructing the circumferential shield 12, it is preferable to create frozen soil in the surrounding ground in advance using a known freezing method, and to appropriately perform earth retaining and water cutting of the surrounding ground. Also, instead of creating frozen soil, or in addition to creating frozen soil, ground improvement by chemical injection or the like may be performed. Note that the circumferential shield 12 is constructed in a circular (donut-shaped) shape starting from the bottom of the starting shaft 11 so as to surround the main line shield 2 and the lamp shield 3. The circumferential shield 12 may be constructed in stages. In Fig. 5, reference numeral 12A denotes the front end face of the constructed circumferential shield 12, and reference numeral 12B denotes the rear end face of the circumferential shield 12. The front end face 12A of the circumferential shield 12 is the end face facing the destination side opposite the starting base 7 (see Fig. 1) in the underground widening section 1. The rear end face 12B of the circumferential shield 12 is the end face opposite the front end face 12A.

[0028] Next, in step S03, as shown in Fig. 6, frozen soil 13 is created so as to cover the front end surface 12A and the rear end surface 12B of the circumferential shield 12. Here, the frozen soil 13 can be created using a known freezing method. In addition, ground improvement may be performed by injecting a chemical solution in conjunction with the creation of the frozen soil 13. Note that the created area of ​​the frozen soil 13 shown in the figure is one example.

[0029] Next, in step S04, while excavating the ground inside the circumferential shield 12, a pair of opposing front and rear walls 14A and 14B are temporarily constructed on the front end face 12A side and the rear end face 12B side of the circumferential shield 12, as shown in FIG. 7, to construct the starting base 7. FIG. 7 shows the circumferential shield 12 and its internal vertical cross-sectional structure. The vertical cross-section here refers to a cross-section along the tunnel axis direction of the underground widening section 1 to be constructed. Also, in FIG. 7, the main line shield 2 penetrating the front wall 14A, and the main line shield 2 and the lamp shield 3 penetrating the rear wall 14B are omitted from illustration. Also, the reference numeral 12C shown in FIG. 7 denotes an entrance formed by removing some segments of the circumferential shield 12. The internal space of the starting shaft 11 is connected to the inside of the circumferential shield 12 through the loading / unloading entrance 12C of the circumferential shield 12, and this entrance 12C is used to discharge excavated soil and other materials generated during ground excavation, and to transport in and out various equipment and materials for constructing the underground widening section 1.

[0030] Here, the structure of the front wall 14A and the rear wall 14B of the circumferential shield 12 is not particularly limited. For example, the front wall 14A and the rear wall 14B may be a steel concrete (steel concrete) structure or a reinforced concrete structure. In this embodiment, the front wall 14A and the rear wall 14B have a circular shape when viewed from the front.

[0031] In this manner, the starting base 7 is formed with the circumferential shield 12, the front flaps 14A, and the rear flaps 14B as its outer shell. The starting base 7 is a base for starting the shield machine for constructing the leading shield 5 and the trailing shield 6, and for example, the shield machine can be assembled on the inner space side of the starting base 7. In addition, a starting opening (not shown) for starting the shield machine for constructing the leading shield 5 and the trailing shield 6 is formed at an appropriate position of the front flaps 14A so as to penetrate the front flaps 14A in the wall thickness direction. In addition, the frozen soil 13 covering the rear end surface 12B of the circumferential shield 12 can be thawed after the rear flaps 14B is constructed.

[0032] Next, in step S05, as shown in FIG. 8, a plurality of leading shields 5 are constructed starting from the starting base 7. More specifically, a leading shield machine (not shown) is launched from a predetermined position of the front flank wall 14A at the starting base 7 to construct the leading shield 5. The leading shields 5 are constructed so as to extend in the longitudinal direction of the outer shell lining body 10 (outer shell shield 4) to be constructed. Here, each leading shield 5 is constructed so as to form a certain interval between adjacent leading shields 5 along the circumferential direction of the outer shell lining body 10 (outer shell shield 4) to be constructed. For example, when the leading shield machine launched from the starting base 7 excavates to the arrival point of the underground widening section 1, it may be returned to the starting base 7 leaving a cutter and a skin plate at the arrival point (tip) and start excavating the next leading shield 5.

[0033] Fig. 9 is a diagram showing a schematic diagram of a state in which construction of a predetermined number of leading shields 5 has been completed. In Fig. 9, the starting shaft 11 and the circumferential shield 12 are omitted from illustration. Fig. 9 is also a perspective view of the leading shields 5 viewed from the arrival point side of the underground widening section 1. In Fig. 9, reference symbol 5A denotes the tip portion located on the arrival point side of each leading shield 5.

[0034] Here, each of the leading shields 5 is arranged in an annular shape as a whole along the circumferential direction of the outer shell lining structure 10 (outer shell shield 4) to be constructed, and the main line shield 2 is surrounded by a group of leading shields consisting of a plurality of leading shields 5 arranged in an annular shape. In this embodiment, a total of 17 leading shields 5 are constructed so as to extend from the starting base 7 toward the destination point side, but the number of leading shields 5 included in the group of leading shields is not particularly limited. In addition, the construction order of the predetermined number of leading shields 5 is not particularly limited. For example, 17 leading shield machines may be started from the starting base 7 at the same time so that all leading shields 5 are constructed in parallel, or the leading shields 5 may be constructed one by one in order. In addition, several leading shield machines (for example, 3 to 5 machines) may be started from the starting base 7 at the same time to construct multiple leading shields 5 in parallel. In addition, the tunnel axis direction of each leading shield 5 does not need to be parallel to the tunnel axis direction of the outer shell lining structure 10 (outer shell shield 4) to be constructed. For example, as in the construction example shown in Fig. 9, each leading shield 5 may be constructed so that the distance between the tunnel axis of each leading shield 5 and the tunnel axis of the outer shell lining body 10 (outer shell shield 4) to be constructed gradually decreases from the starting base 7 side toward the arrival point side. As a result, the size of the leading shield group consisting of multiple leading shields 5 arranged in a ring shape gradually tapers from the starting base 7 side toward the arrival point side.

[0035] FIG. 10 is a diagram for explaining a cross section of the leading shield 5. FIG. 10 shows three leading shields 5 out of 17 leading shields 5 arranged in a ring shape as a whole. As shown in FIG. 1 and FIG. 2, the outer shell shield 4 is formed by connecting the leading shields 5 and the trailing shields 6 alternately in a rosary shape. As will be described in detail later, the trailing shield machine for constructing the trailing shield 6 departs from the departure base 7 and excavates between the adjacent leading shields 5 while cutting a part of the segment of the leading shield 5. Therefore, in this embodiment, the area of ​​the leading shield 5 that overlaps with the trailing shield 6 is formed by a cutting segment 52 (the area is shown by hatching in FIG. 10) that can be cut by the trailing shield machine, and the other area is formed by a non-cutting segment 51. This type of cutting segment 52 is well known, and can be formed by including, for example, lightweight aggregate concrete, carbon fiber reinforcement, etc. Also, the non-cutting segment 51 is a normal steel segment. The distance between adjacent leading shields 5 is set to a dimension smaller than the diameter of the trailing shield 6.

[0036] The boundary position of the non-cutting segment 51 and the cutting segment 52 in the leading shield 5 should be set taking into consideration the above-mentioned construction errors so that the trailing shield machine will not interfere with the non-cutting segment 51 even if the actual constructed positions of the leading shield 5 and the trailing shield 6 deviate slightly from their planned positions due to construction errors, etc. Note that, since the trailing shield 6 has not yet been constructed at the stage immediately after the leading shield 5 is constructed, the trailing shield 6 is shown by a dashed line in Figure 10.

[0037] Next, in step S06, as shown in Fig. 11, freezing pipes 53 extending in the axial direction of the leading shield 5 are installed inside the non-cutting segments 51 (steel segments) of each leading shield 5. The freezing pipes 53 are fixed to the upper part of the leading shield 5 (the inner surface of the non-cutting segment 51) and the lower part of the leading shield 5 (the inner surface of the non-cutting segment 51) by, for example, a so-called U-band. Note that, in the example shown in Fig. 11, three freezing pipes 53 are installed at each of the upper and lower parts of the leading shield 5, but the number of freezing pipes 53 installed is not particularly limited.

[0038] In this embodiment, the up-down direction in the cross section of each leading shield 5 corresponds to the direction along the radial direction perpendicular to the circumferential direction of the outer shield 4 to be constructed. Specifically, the upper part of the leading shield 5 refers to the part located on the radially outer periphery side of the outer shield 4 to be constructed. Similarly, the lower part of the leading shield 5 refers to the part located on the radially inner periphery side of the outer shield 4 to be constructed. The width direction in the cross section of the leading shield 5 is a direction perpendicular to the up-down direction of the leading shield 5, and corresponds to the direction along the circumferential direction of the outer shield 4 to be constructed. In other words, the up-down direction and width direction in the cross section of the leading shield 5 indicate a relative positional relationship with the outer shield 4 to be constructed as a reference. The same is true for the trailing shield 6 that is constructed later.

[0039] In this embodiment, the freezing pipes 53 arranged along the axial direction of the leading shield 5 are covered with a covering material 54 such as mortar or concrete. Furthermore, the covering material 54 covering the freezing pipes 53 is further covered with a heat insulating material 55 such as urethane foam. Note that materials and equipment for installing the freezing pipes 53, the covering material 54, the heat insulating material 55, etc. can be carried into the leading shield 5 through the departure shaft 11 and the departure base 7. The installation of the freezing pipes 53, the covering material 54, and the heat insulating material 55 is performed sequentially from the tip 5A side of the leading shield 5 toward the departure base 7 side.

[0040] Here, the reference symbol L1 shown in FIG. 11 is a virtual boundary line indicating the boundary position between the cutting area A1 and the non-cutting area A2 in the internal area (inner space area) of each leading shield 5. The cutting area A1 is an area that will be cut by the trailing shield machine when the trailing shield 6 is constructed later, and the cutting element 56 is formed in the area. The non-cutting area A2 is an area that will not be cut by the trailing shield machine when the trailing shield 6 is constructed later. The reference symbol L2 shown in FIG. 11 is a virtual boundary line indicating the boundary position between the outer shell body construction area A21 and the outer shell body external areas A22, A23 in the non-cutting area A2 in each leading shield 5. In the outer shell body construction area A21, a leading outer shell body part 9A described later is constructed. In addition, the outer shell body external areas A22, A23 are filled with liquefied treated soil as described later. In the cross section of each preceding shield 5, the cutting areas A1 are located on both sides in the width direction of the preceding shield 5, and the non-cutting areas A2 are positioned as areas sandwiched between the left and right cutting areas A1. Furthermore, of the non-cutting areas A2, the outer shell structure construction area A21 is positioned in the area on the vertical center side of the preceding shield 5. Furthermore, the outer shell structure external area A22 is positioned in the lower area of ​​the non-cutting area A2, and the outer shell structure external area A23 is positioned in the upper area of ​​the non-cutting area A2.

[0041] Next, in step S07, as shown in Fig. 12, cutting elements 56 are constructed in the cutting area A1 of each leading shield 5, and leading outer shell body parts 9A are constructed in the outer shell body construction area A21. In addition, non-structural elements 57, 58 are constructed by filling the outer shell body external areas A22, A23 of each leading shield 5 with liquefied treated soil. Fig. 12 is a schematic diagram showing the cutting elements 56, leading outer shell body parts 9A, and non-structural elements 57, 58 constructed inside each leading shield 5.

[0042] The cutting element 56, the leading shell body part 9A, and the non-structural elements 57 and 58 are extended along the axial direction of each leading shield 5. The order in which the cutting element 56, the leading shell body part 9A, and the non-structural elements 57 and 58 are constructed is not particularly limited. The cutting element 56, the leading shell body part 9A, and the non-structural elements 57 and 58 can be constructed sequentially from the tip part 5A side toward the starting base 7. For example, the cutting element 56, the leading shell body part 9A, and the non-structural elements 57 and 58 may be constructed sequentially for each work section, with a length of about 10 m along the axial direction of the leading shield 5.

[0043] Here, the cutting elements 56 are constructed by filling the cutting area A1 of the leading shield 5 with liquefied treated soil. By filling the cutting area A1 of the leading shield 5 with liquefied treated soil and forming the cutting elements 56, the cutting segments 52 in the leading shield 5 can be stably cut when the trailing shield 6 is constructed later. Note that the cutting elements 56 may be formed using air mortar instead of liquefied treated soil. Furthermore, the cutting area A1 of the leading shield 5 is designed so that the trailing shield machine will not collide with the leading outer shell structure 9A even if the actual construction positions of the leading shield 5 and the trailing shield 6 are slightly deviated from the planned positions. It is advisable to set the width wider, taking into consideration construction errors. Also, the non-structural elements 57 and 58 may be constructed using air mortar instead of liquefied treated soil.

[0044] Next, the leading outer shell body part 9A constructed in the outer shell body construction area A21 of the leading shield 5 will be described. The leading outer shell body part 9A is a structural body forming a part of the outer shell ring body 9. Specifically, the leading outer shell body part 9A and the trailing outer shell body part 9B constructed inside the segment of the trailing shield 6 constructed later are integrated to form the outer shell ring body 9.

[0045] As shown in Fig. 12, the leading outer shell structure portion 9A includes a leading inner periphery side steel shell element 91A and a leading outer periphery side steel shell element 91B arranged in two tiers, one above the other, in the outer shell structure construction area A21 of the leading shield 5, and a structure concrete 92 constructed by filling concrete between each of these steel shell elements 91A and 91B. The leading inner periphery side steel shell element 91A is arranged in the lower tier in the cross section of the leading shield 5, and is located on the radial inner periphery side of the outer shell shield 4 to be constructed. On the other hand, the leading outer periphery side steel shell element 91B is arranged in the upper tier in the cross section of the leading shield 5, and is located on the radial outer periphery side of the outer shell shield 4 to be constructed.

[0046] The leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B have a common basic structure, and are horizontally laid along the circumferential direction of the outer shell shield 4 to be constructed so as to cross the leading shield 5. In addition, the concrete constituting the concrete structure 92 is boxed out from the end regions of the leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B so that they are not buried in the concrete structure 92.

[0047] First, a detailed structure of the leading inner periphery side steel-shell element 91A will be described with reference to Fig. 13 to Fig. 15. Fig. 13 is a plan view of the leading inner periphery side steel-shell element 91A. Fig. 14 is a front view of the leading inner periphery side steel-shell element 91A as viewed from the direction B in Fig. 13. Fig. 15 is a side view of the leading inner periphery side steel-shell element 91A as viewed from the direction C in Fig. 13.

[0048] The leading inner circumference side steel shell element 91A is a unit including the leading side edge cutting steel plate 40A and a plurality of leading side main girder steel plates 30A erected from the leading side edge cutting steel plate 40A. In this embodiment, the leading inner circumference side steel shell element 91A unitized in this manner is extended from the tip 5A of the leading shield 5 to the starting base 7 by being connected along the axial direction of the leading shield 5.

[0049] 13, the leading-side edge cutting steel plate 40A is a steel plate having a substantially rectangular plane. In this embodiment, the long side direction of the leading-side edge cutting steel plate 40A is arranged along the width direction of the leading shield 5, and the short side direction of the leading-side edge cutting steel plate 40A is arranged along the axial direction of the leading shield 5.

[0050] Reference numerals 401A and 405A denote a first side and a second side extending along the long side direction of the leading-side edge cutting steel plate 40A, and reference numeral 402A denotes an end face extending along the short side direction of the leading-side edge cutting steel plate 40A. Reference numeral 403A denotes a main girder support surface of the leading-side edge cutting steel plate 40A. In the example shown in FIG. 13 and FIG. 15, three leading-side main girder steel plates 30A are supported by the main girder support surface 403A of the leading-side edge cutting steel plate 40A. Reference numeral 404A denotes a cutting surface located on the opposite side of the main girder support surface 403A of the leading-side edge cutting steel plate 40A.

[0051] The first side surface 401A of the leading-side edge cutting steel plate 40A is arranged so as to face the tip portion 5A side of the leading shield 5 when the leading inner circumferential side steel shell element 91A is installed in the outer shell construction area A21 of the leading shield 5. On the other hand, the second side surface 405A of the leading-side edge cutting steel plate 40A is arranged so as to face the tip portion 5A side of the leading shield 5 when the leading inner circumferential side steel shell element 91A is installed in the outer shell construction area A21 of the leading shield 5. When the inner circumference side steel shell element 91A is installed in the outer shell body construction area A21 of the leading shield 5, it is arranged so as to face the opposite side to the tip 5A of the leading shield 5 (i.e., the starting base 7 side). In addition, when the leading inner circumference side steel shell element 91A is installed in the outer shell body construction area A21 of the leading shield 5, the edge cutting surface 404A of the leading side edge cutting steel plate 40A is arranged so as to face the lower side of the leading shield 5 (the inner circumference side of the outer shell shield 4). In addition, the leading side edge cutting steel plate 40A of the leading inner circumference side steel shell element 91A is curved in an arc shape so as to follow the circumferential direction of the outer shell shield 4 to be constructed when viewed from the front.

[0052] The leading-side main girder steel plate 30A is a structural steel plate whose outer shape is defined by a first main surface 301A, a second main surface 302A, a top surface 303A, a bottom surface 304A, and a pair of end surfaces 305A. The leading-side main girder steel plate 30A is erected from the main girder support surface 403A of the leading-side edge cutting steel plate 40A so as to extend along the long side direction of the leading-side edge cutting steel plate 40A. The leading-side main girder steel plate 30A is integrally structured with the leading-side edge cutting steel plate 40A by joining its bottom surface 304A to the main girder support surface 403A of the leading-side edge cutting steel plate 40A. As shown in FIG. 14, the leading-side main girder steel plate 30A is curved in a front view so as to follow the circumferential direction of the outer shell shield 4 to be constructed, similar to the leading-side edge cutting steel plate 40A.

[0053] The three leading-side main girder steel plates 30A erected from the leading-side edge cutting steel plate 40A are arranged parallel to each other and at regular intervals. Hereinafter, the direction in which the leading-side main girder steel plate 30A extends along the long side direction of the leading-side edge cutting steel plate 40A is referred to as the "longitudinal direction". As shown in Figures 13 and 14, each end face 305A of each leading-side main girder steel plate 30A is aligned with the end face 402A of the leading-side edge cutting steel plate 40A.

[0054] A perforated steel plate dowel (hereinafter referred to as "preceding side perforated steel plate dowel") 32A is rigidly joined to both ends of the leading side main girder steel plate 30A in the longitudinal direction by welding or the like. The leading side perforated steel plate dowel 32A has a substantially rectangular planar shape, and one long side is connected along the first main surface 301A of the leading side main girder steel plate 30A. The leading side perforated steel plate dowel 32A stands upright from the first main surface 301A of the leading side main girder steel plate 30A so as to face the main girder holding surface 403C of the leading side edge cutting steel plate 40A. As shown in FIG. 15, the leading side perforated steel plate dowel 32A is installed at a height near the center in the up-down direction of the leading side main girder steel plate 30A. As shown in FIG. 15, a gap V1 is formed between the side surface of the leading-side perforated steel plate dowel 32A and the second principal surface 302A of the leading-side main girder steel plate 30A with which the side surface faces.

[0055] As shown in Figs. 13 and 15, the leading side perforated steel plate dowel 32A has a plurality of dowel holes 320 drilled therethrough in the thickness direction of the leading side perforated steel plate dowel 32A. In the example shown in Fig. 13, a total of 10 dowel holes 320 are arranged vertically and horizontally in two rows in the short side direction and five rows in the long side direction of the leading side perforated steel plate dowel 32A. The dowel holes 320 have a circular cross section. However, the number, position, size, arrangement pattern, and other aspects of the dowel holes 320 formed in the leading side perforated steel plate dowel 32A are not particularly limited. Here, of the two rows of dowel holes 320 in the leading side perforated steel plate dowel 32A, the row closer to the first main surface 301A of the leading side main girder steel plate 30A may be called the "first row" and the row farther from it may be called the "second row".

[0056] Here, the reference symbol AE1 shown in Fig. 14 denotes an end region in the long side direction (longitudinal direction) of the leading inner circumference side steel shell element 91A. The end region AE1 of the leading inner circumference side steel shell element 91A includes leading side perforated steel plate dowels 32A formed on both ends of the leading side main girder steel plate 30A.

[0057] Next, referring to Figs. 16 to 18, the detailed structure of the leading outer peripheral steel shell element 91B will be described. Fig. 16 is a plan view of the leading outer peripheral side steel-shell element 91B. Fig. 17 is a front view of the leading outer peripheral side steel-shell element 91B as viewed from the D direction in Fig. 16. Fig. 18 is a side view of the leading outer peripheral side steel-shell element 91B as viewed from the E direction in Fig. 16.

[0058] The basic structure of the leading outer periphery side steel shell element 91B is the same as that of the leading inner periphery side steel shell element 91A described above. In the following, the components of the leading outer periphery side steel shell element 91B that are common to the leading inner periphery side steel shell element 91A are denoted by the same reference numerals and will not be described in detail.

[0059] The leading outer shell element 91B is a unit including a leading edge cutting steel plate 40A and a plurality of leading main girder steel plates 30A erected from the leading edge cutting steel plate 40A, similar to the leading inner shell element 91A. Similarly to the leading inner shell element 91A, the leading outer shell element 91B is also connected along the axial direction of the leading shield 5.

[0060] In the leading outer periphery side steel shell element 91B, the leading side edge cutting steel plate 40A and the leading side main girder steel plate 30A are also curved in an arc shape along the circumferential direction of the outer shell shield 4 to be constructed in a front view. When the leading outer periphery side steel shell element 91B is installed in the outer shell body construction area A21 of the leading shield 5, the leading side edge cutting steel plate 40A in the leading outer periphery side steel shell element 91B is arranged so that the first side surface 401A of the leading side edge cutting steel plate 40A faces the tip portion 5A side of the leading shield 5, the second side surface 405A of the leading side edge cutting steel plate 40A faces the starting base 7 side, and the edge cutting surface 404A of the leading side edge cutting steel plate 40A faces the upper side of the leading shield 5 (the outer periphery side of the outer shell shield 4).

[0061] In addition, the leading-side main girder steel plate 30A of the leading outer periphery side steel shell element 91B also has leading-side perforated steel plate dowels 32A at both ends in the longitudinal direction. As shown in Fig. 18, the leading-side perforated steel plate dowels 32A are installed at a height near the center in the up-down direction of the leading-side main girder steel plate 30A. Also, the reference symbol AE2 shown in Fig. 17 is an end region in the long side direction (longitudinal direction) of the leading outer periphery side steel shell element 91B. The end region AE2 in the leading outer periphery side steel shell element 91B includes the leading-side perforated steel plate dowels 32A formed at both ends of the leading-side main girder steel plate 30A.

[0062] The leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B configured as described above are positioned and fixed at predetermined positions in the outer shell body construction area A21 of the leading shield 5 as shown in Fig. 19. Fig. 19 is a diagram showing a state in which the leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B are installed in the outer shell body construction area A21 of the leading shield 5. The leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B may be installed at the predetermined positions shown in Fig. 19 by a positioning bracket or a stand attached to the segment in the leading shield 5. Note that the example shown in Fig. 19 shows a situation after the outer shell body construction area A21 of the leading shield 5 is filled with liquefied treated soil and the cutting element 56 is constructed.

[0063] Here, FIG. 20 is a diagram showing a schematic arrangement of the leading inner periphery side steel shell elements 91A (leading outer periphery side steel shell elements 91B) along the axial direction of the leading shield 5. As shown in FIG. 20, when constructing the leading outer shell body part 9A, a plurality of leading inner periphery side steel shell elements 91A (leading outer periphery side steel shell elements 91B) are arranged in series along the axial direction of the leading shield 5. The leading outer shell body part 9A is constructed sequentially from the tip part 5A side of the leading shield 5 toward the starting base 7. The plurality of leading inner periphery side steel shell elements 91A (leading outer periphery side steel shell elements 91B) arranged in series along the axial direction of the leading shield 5 can be joined in a state in which the second side surface 405A of the leading side edge cutting steel plate 40A is butted against the first side surface 401A of the counterpart leading side edge cutting steel plate 40A connected to the leading side edge cutting steel plate 40A. The method of joining the side surfaces 401A, 405A of the leading edge cutting steel plate 40A is not particularly limited, and a splice plate may be used. The joints may be welded or bolted.

[0064] Also, reference numeral 15 shown in Figures 19 and 20 denotes a box punching formwork installed in the end regions AE1, AE2 of the leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B. The box punching formwork 15 is installed so as to cover the end regions AE1, AE2 of the leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B positioned and fixed at a predetermined position in the outer shell body construction region A21 of the leading shield 5. Reference numeral 16 denotes a hollow portion (hereinafter referred to as "box punching portion") inside the box punching formwork 15. The end regions AE1, AE2 of the leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B are arranged in the box punching portion 16 formed by the box punching formwork 15.

[0065] As described above, after the installation of the leading inner periphery side steel shell element 91A and the leading outer periphery side steel shell element 91B in the outer shell construction area A21 of the leading shield 5 is completed, the concrete structure 92 and the non-structural elements 57, 58 are constructed in an appropriate order. For example, in the case of the leading shield 5 located on the top side of the outer shell shield 4 to be constructed, the outer shell structure external area A22 is located on the lower side in the direction of gravity in the leading shield 5, the outer shell structure external area A23 is located on the upper side in the direction of gravity, and the outer shell structure construction area A21 is located in a position sandwiched between them. In this embodiment, the concrete structure 92 and the non-structural elements 57, 58 are constructed in order or in parallel from the lower side to the upper side in the direction of gravity depending on the location of each leading shield 5. For example, when the outer shell skeleton external area A22 is located on the lower side in the direction of gravity and the outer shell skeleton external area A23 is located on the upper side in the direction of gravity in the preceding shield 5, first, as shown in Fig. 21, the outer shell skeleton external area A22 located on the lower side in the direction of gravity is filled with liquefied treated soil to construct the non-structural element 57. Next, as shown in Fig. 22, concrete is poured in the outer shell skeleton construction area A21 to construct the skeleton concrete 92.

[0066] Then, the outer shell skeleton external area A23 located on the upper side in the gravity direction is filled with liquefied treated soil to construct the non-structural element 58. As a result, as shown in FIG. 12, the leading outer shell skeleton part 9A and the non-structural elements 57, 58 are constructed in the leading shield 5. When constructing the concrete skeleton 92 in the outer shell skeleton construction area A21, concrete is poured in the area sandwiched between the leading side edge cutting steel plate 40A (main girder holding surface 403A) of the leading inner periphery side steel shell element 91A and the leading side edge cutting steel plate 40A (main girder holding surface 403A) of the leading outer periphery side steel shell element 91B. At that time, the leading side main girder steel plate 30A of each steel shell element 91A, 91B is covered with concrete to be integrated with the concrete skeleton 92, except for the end areas AE1, AE2 covered with the box punching formwork 15. As a result, the preceding shell skeleton portion 9A consisting of the steel shell elements 91A, 91B and the skeleton concrete 92 is constructed.

[0067] Conversely, in the case of the preceding shield 5 arranged on the bottom side of the outer shell shield 4 to be constructed, the outer shell skeleton external area A22 is located on the upper side in the direction of gravity, the outer shell skeleton external area A23 is located on the lower side in the direction of gravity, and the outer shell skeleton construction area A21 is located in a position sandwiched between them. In this case, the construction order is reversed from the above example, and the non-structural element 58 is first constructed in the outer shell skeleton external area A23 located on the lower side in the direction of gravity, and then the skeleton concrete 92 is constructed by pouring concrete in the outer shell skeleton construction area A21, and finally the non-structural element 57 is constructed in the outer shell skeleton external area A22 located on the upper side in the direction of gravity. Alternatively, in the case of the preceding shield 5 arranged on the side of the outer shell shield 4 to be constructed, the skeleton concrete 92 and the non-structural elements 57 and 58 may be constructed in parallel or in stages from the lower side to the upper side in the direction of gravity. In this way, the order of construction of the concrete body 92 and the non-structural elements 57, 58 within the leading shield 5 can be changed as appropriate depending on the location of the leading shield 5, specifically, in relation to the direction of gravity.

[0068] In addition, the non-structural element 57 and the concrete structure 92 in the leading shield 5 are separated by the leading-side edge-cutting steel plate 40A of the leading inner-circumference steel shell element 91A, and the non-structural element 58 and the concrete structure 92 are separated by the leading-side edge-cutting steel plate 40A of the leading outer-circumference steel shell element 91B. In addition, in step S07, the length of the leading outer shell structure part 9A constructed by one concrete pouring (the length of one section of the leading outer shell structure part 9A) is not particularly limited, but may be, for example, about 10 m. The leading outer shell structure part 9A can be constructed in the entire section of the leading shield 5 by sequentially extending the leading outer shell structure part 9A from the tip part 5A side of the leading shield 5 toward the starting base 7 side. In addition, instead of filling the outer shell structure external areas A22, A23 of the leading shield 5 with liquefied treated soil, the outer shell structure external areas A22, A23 may be filled with concrete. That is, the concrete structure 92 may be constructed in the outer regions A22 and A23 of the outer shell structure of the preceding shield 5.

[0069] Next, the construction of the trailing shield 6 will be described. In step S08, as shown in FIG. 23, the trailing shield 6 is constructed. The trailing shield 6 is constructed by a trailing shield machine starting from a starting base 7, which excavates between a pair of adjacent leading shields 5 while cutting the cutting segments 52 and cutting elements 56 of the leading shield 5. Note that in FIG. 23, the starting shaft 11 and the circumferential shield 12 are omitted from illustration. Also, the trailing shields 6 can be constructed one by one in order. That is, the trailing shield machine, which excavates from the starting base 7, may excavate up to the tip 6A (see FIG. 25 described later) of the trailing shield 6 on the arrival point side, and then may be temporarily returned to the starting base 7 while leaving the cutter and skin plate at the tip 6A, and may start excavating the next trailing shield 6.

[0070] Fig. 24 is a diagram showing a cross section of the constructed trailing shield 6. The segments of the trailing shield 6 are composed of steel segments 61. As shown in Fig. 24, the leading shields 5 and the trailing shields 6 are arranged alternately, and partially overlap in a cross section perpendicular to the axial direction of the shields. Note that Fig. 24 shows a schematic cross section of some of the leading shields 5 and trailing shields 6 included in the outer shell shield 4.

[0071] FIG. 25 is a diagram showing a schematic diagram of a state in which the construction of a predetermined number of trailing shields 6 has been completed. In this embodiment, a total of 17 trailing shields 6 extend from the starting base 7 toward the arrival point side, but the number of the trailing shields 6 is not particularly limited. In addition, the construction order of the predetermined number of trailing shields 6 is not particularly limited. For example, 17 trailing shield machines may be started from the starting base 7 at the same time so that all the trailing shields 6 are constructed in parallel, or the trailing shields 6 may be constructed one by one in order. In addition, several trailing shield machines (e.g., 3 to 5) may be started from the starting base 7 at the same time to construct multiple trailing shields 6 in parallel. As shown in FIG. 25, the leading shield 5 and the trailing shield 6 are mutually connected in a rosary-like manner. As a result, an outer shell shield 4 is formed that has an annular (ring-shaped) cross section and a generally cylindrical shape as a whole. That is, in this embodiment, the outer shell shield 4 is constructed by connecting the segments of 34 small cross-section shield tunnels (17 each of the leading shield 5 and the trailing shield 6) in a rosary shape. The frozen soil 13 covering the front end face 12A of the circumferential shield 12 can be thawed after the construction of all the trailing shields 6. In the example shown in Fig. 25, the outer shell shield 4 gradually narrows in diameter from the starting base 7 toward the destination point.

[0072] Next, in step S09, as shown in Fig. 26, freezing tubes 63 are installed inside the steel segments 61 of each trailing shield 6. Fig. 26 is a schematic cross-sectional view of a portion of the leading shield 5 and trailing shield 6 included in the outer shell shield 4. The freezing tubes 63 are fixed to the inner surfaces of the steel segments 61 at the upper and lower parts of the trailing shield 6, for example, by so-called U-bands. In the example shown in Fig. 26, three freezing tubes 63 are installed at the upper and lower parts of the trailing shield 6, respectively. Although four freezing pipes 63 are installed, the number of freezing pipes 63 to be installed is not particularly limited. Here, the freezing pipes 63 are covered with a covering material 64 such as mortar or concrete. Furthermore, the covering material 64 covering the freezing pipes 63 is further covered with a heat insulating material 65 such as urethane foam. The freezing pipes 63 extend along the axial direction of the trailing shield 6. Furthermore, materials such as the freezing pipes 63, the covering material 64, the heat insulating material 65, etc., as well as the equipment for installing these, can be carried into the trailing shield 6 through the departure shaft 11 and the departure base 7.

[0073] Next, in step S10, brine is poured into the freezing pipe 53 of the leading shield 5 and the freezing pipe 63 of the trailing shield 6 to create frozen soil 41, 42 on the outer and inner sides of the outer shield 4. FIG. 27 shows the state in which the frozen soil 41, 42 has been created on the outer and inner sides of the outer shield 4, and also shows cross sections of a portion of the leading shield 5 and the trailing shield 6 included in the outer shield 4. The frozen soil 41 is a ring-shaped frozen soil that surrounds the outer shield 4, and the frozen soil 42 is a ring-shaped frozen soil that surrounds the inner side of the outer shield 4. The thickness of the frozen soil 41, 42 can be appropriately determined based on the surrounding earth pressure, water pressure, depth, soil quality, and diameters of the leading shield 5 and the trailing shield 6 in the outer shield 4.

[0074] Next, in step S11, as shown in FIG. 27, a part of the steel segment 61 in the trailing shield 6 is cut open to connect the trailing shield 6 and the leading shield 5. Specifically, at the side of the trailing shield 6 overlapping with the leading shield 5, the skin plate is removed while leaving the main girder of the steel segment 61 in place. Then, the cutting element 56 formed by the liquefied treated soil filled in the cutting area A1 of the leading shield 5 is removed. A heavy machine such as a backhoe is used to remove the cutting element 56 (liquefied treated soil). The skin plate of the removed steel segment 61 and the cutting element 56 (liquefied treated soil) can be discharged using a carrying vehicle. Appropriate waterproofing treatment can be performed at the connection point between the leading shield 5 and the trailing shield 6, such as by installing a waterproof sheet.

[0075] Next, in step S12, as shown in FIG. 28, a trailing outer shell body part 9B is constructed inside the trailing shield 6. The trailing outer shell body part 9B is a structural body forming a part of the outer shell ring body 9, and is extended from the tip part 6A to the starting base 7 along the axial direction of each trailing shield 6. The trailing outer shell body part 9B is configured to include a trailing inner circumference side steel shell element 93A and a trailing outer circumference side steel shell element 93B arranged in two stages, upper and lower, in the trailing shield 6, and a concrete body 95 constructed by filling concrete between each of these steel shell elements 93A and 93B. The trailing inner circumference side steel shell element 93A is arranged in the lower stage in the cross section of the trailing shield 6, and is located on the radial inner circumference side of the outer shell shield 4. On the other hand, the trailing outer peripheral steel shell element 93B is disposed in an upper stage in the cross section of the trailing shield 6, and is positioned on the outer peripheral side of the outer shell shield 4 in the radial direction.

[0076] The trailing inner periphery side steel shell element 93A and the trailing outer periphery side steel shell element 93B have a common basic structure, and are horizontally mounted along the circumferential direction of the outer shell shield 4 so as to cross the trailing shield 6. The trailing inner periphery side steel shell element 93A is integrally connected to the end of the leading inner periphery side steel shell element 91A in the leading shield 5 adjacent to both sides of the trailing shield 6, and the trailing outer periphery side steel shell element 93B in the trailing shield 6 is integrally connected to the end of the leading outer periphery side steel shell element 91B in the leading shield 5 adjacent to both sides of the trailing shield 6.

[0077] As shown in Fig. 28, non-structural elements 67, 68 are constructed in the region below the trailing inner steel shell element 93A and above the trailing outer steel shell element 93B inside the segment of the trailing shield 6. The non-structural elements 67, 68 can be constructed, for example, by filling the segment with liquefied treated soil. Also, the non-structural elements 67, 68 may be constructed using air mortar instead of liquefied treated soil. Hereinafter, within the trailing shield 6, the area in which the trailing outer shell body portion 9B is constructed will be referred to as an outer shell body construction area B21, and the areas in which the non-structural elements 67, 68 are constructed will be referred to as outer shell body outer areas B22, B23, respectively.

[0078] First, the trailing inner circumference side steel shell element 93A will be described. FIG. 29 is a plan view of the trailing inner circumference side steel shell element 93A. The trailing inner circumference side steel shell element 93A is configured to include a first steel shell unit 94A having a trailing side first main girder steel plate 30B and a trailing side second main girder steel plate 30C combined with the first steel shell unit 94A. As shown in FIG. 29, the first steel shell unit 94A and the trailing side second main girder steel plate 30C are separated from each other. In the following, the trailing side first main girder steel plate 30B and the trailing side second main girder steel plate 30C may be collectively referred to as the "trailing side main girder steel plate".

[0079] The first steel shell unit 94A is configured to include a trailing-side edge cutting steel plate 40B having a substantially rectangular plane, and a plurality of trailing-side first main girder steel plates 30B erected from the trailing-side edge cutting steel plate 40B. In this embodiment, a plurality of first steel shell units 94A are arranged in series along the axial direction of the trailing shield 6. FIG. 30 is a front view of the first steel shell unit 94A as viewed from the F direction in FIG. 29. FIG. 31 is a side view of the first steel shell unit 94A as viewed from the G direction in FIG. 29. FIG. 32 is a side view of the first steel shell unit 94A as viewed from the H direction in FIG. 29.

[0080] Reference numerals 401B and 405B denote the first and second side faces extending along the long side of the trailing-side edge cutting steel plate 40B, and reference numerals 402B and 406B denote the outer end face and inner end face extending along the short side of the trailing-side edge cutting steel plate 40B. Reference numeral 403B denotes the main girder holding surface of the trailing-side edge cutting steel plate 40B, and in the example shown in FIG. 29, three trailing-side first main girder steel plates 30B are integrally held by the main girder holding surface 403B. Reference numeral 404B denotes the edge cutting surface located on the opposite side of the main girder holding surface 403B of the trailing-side edge cutting steel plate 40B. Reference numeral 407 denotes a notch provided on the outer end face 406B side of the trailing-side edge cutting steel plate 40B. The cutout portion 407 is formed from the outer end surface 406B of the trailing-side edge cutting steel plate 40B along the long side direction of the trailing-side edge cutting steel plate 40B. The cutout portion 407 of the trailing-side edge cutting steel plate 40B is an opening for preventing interference between the main girder of the steel segment 61 and the trailing-side edge cutting steel plate 40B when the first steel shell unit 94A is installed on the trailing shield 6.

[0081] The first side surface 401B of the trailing side edge cutting steel plate 40B in the first steel shell unit 94A is arranged so as to face the tip 6A side of the trailing shield 6 when the first steel shell unit 94A is installed inside the segment of the trailing shield 6. On the other hand, the second side surface 405B of the trailing side edge cutting steel plate 40B is arranged so as to face the opposite side to the tip 6A of the trailing shield 6 when the first steel shell unit 94A is installed inside the segment of the trailing shield 6. In addition, the edge cutting surface 404B of the trailing side edge cutting steel plate 40B is arranged so as to face the lower side of the trailing shield 6 (the inner peripheral side of the outer shell shield 4) when the first steel shell unit 94A is installed inside the segment of the trailing shield 6. In addition, the trailing side edge cutting steel plate 40B of the first steel shell unit 94A is curved in an arc shape along the circumferential direction of the outer shell shield 4 in a front view.

[0082] The trailing-side first main girder steel plate 30B is a structural steel plate whose outer shape is defined by a first main surface 301B, a second main surface 302B, a top surface 303B, a bottom surface 304B, an outer end surface 305B, and an inner end surface 306B. The trailing-side first main girder steel plate 30B stands upright from the main girder support surface 403B of the trailing-side edge cutting steel plate 40B so as to extend along the long side direction of the trailing-side edge cutting steel plate 40B. The trailing-side first main girder steel plate 30B is integrally formed with the trailing-side edge cutting steel plate 40B by joining its bottom surface 304B to the main girder support surface 403B of the trailing-side edge cutting steel plate 40B. As shown in FIG. 30, the trailing-side first main girder steel plate 30B is curved along the circumferential direction of the outer shell shield 4 in a front view, similar to the trailing-side edge cutting steel plate 40B. The first of the first main girder steel plate 30B on the trailing side The main surface 301B is disposed so as to face the tip 6A of the trailing shield 6 when the first steel shell unit 94A is installed inside the segment of the trailing shield 6. The second main surface 302B of the trailing-side first main girder steel plate 30B is disposed so as to face the side opposite the tip 6A of the trailing shield 6 when the first steel shell unit 94A is installed inside the segment of the trailing shield 6.

[0083] In addition, the three trailing-side first main girder steel plates 30B erected from the trailing-side edge cutting steel plate 40B are arranged parallel to each other and at regular intervals. Hereinafter, the direction in which the trailing-side first main girder steel plate 30B extends along the long side direction of the trailing-side edge cutting steel plate 40B is referred to as the "longitudinal direction". As shown in Figures 29 and 30, the longitudinal dimension of the trailing-side first main girder steel plate 30B is longer than the long side dimension of the trailing-side edge cutting steel plate 40B, and each end face 402B, 406B of the trailing-side edge cutting steel plate 40B is arranged in a position retreated to the inside from each end face 305B, 306B of the trailing-side first main girder steel plate 30B.

[0084] Hereinafter, the end of the trailing-side first main girder steel plate 30B located on the outer end surface 305B side is referred to as the outer end, and the end of the trailing-side first main girder steel plate 30B located on the inner end surface 306B side is referred to as the inner end. A trailing-side first perforated steel plate dowel 32B is provided at the outer end of the trailing-side first main girder steel plate 30B, and a trailing-side second perforated steel plate dowel 32C is provided at the inner end of the trailing-side first main girder steel plate 30B. The trailing-side first perforated steel plate dowel 32B and the trailing-side second perforated steel plate dowel 32C are rigidly joined to the second main surface 302B of the trailing-side first main girder steel plate 30B by welding or the like. The trailing-side first perforated steel plate dowel 32B and the trailing-side second perforated steel plate dowel 32C are joined to the second main surface 302B of the trailing-side first main girder steel plate 30B so as to be arranged substantially parallel to and facing the main girder supporting surface 403B of the trailing-side edge cutting steel plate 40B. Also, as shown in Fig. 30 and Fig. 31, the trailing-side first perforated steel plate dowel 32B and the trailing-side second perforated steel plate dowel 32C are joined at a position (height) lower than the center in the up-down direction of the trailing-side first main girder steel plate 30B.

[0085] In addition, a plurality of dowel holes 320 having a circular cross section are drilled through the trailing-side first perforated steel sheet dowel 32B and the trailing-side second perforated steel sheet dowel 32C in the sheet thickness direction. In the example shown in FIG. 29, a total of 10 dowel holes 320 are arranged vertically and horizontally in two rows in the short side direction and five rows in the long side direction of the trailing-side first perforated steel sheet dowel 32B. In addition, a total of 14 dowel holes 320 are arranged vertically and horizontally in two rows in the short side direction and seven rows in the long side direction of the trailing-side second perforated steel sheet dowel 32C. However, the number, position, size, arrangement pattern, and other aspects of the dowel holes 320 formed in the trailing-side first perforated steel sheet dowel 32B and the trailing-side second perforated steel sheet dowel 32C are not particularly limited. In addition, among the dowel holes 320 in the trailing side first perforated steel plate dowel 32B and the trailing side second perforated steel plate dowel 32C, the row closer to the second main surface 302C of the trailing side first main girder steel plate 30B may be referred to as the "first row" and the row farther away may be referred to as the "second row".

[0086] Next, the trailing-side second main girder steel plate 30C will be described. The trailing-side second main girder steel plate 30C is a long structural steel plate having substantially the same shape as the trailing-side first main girder steel plate 30B, and is provided at its end with a trailing-side first perforated steel plate dowel 32B and a trailing-side second perforated steel plate dowel 32C.

[0087] FIG. 33 is a front view of the trailing-side second main girder steel plate 30C as viewed from the I direction in FIG. 29. FIG. 34 is a side view of the trailing-side second main girder steel plate 30C as viewed from the J direction in FIG. The trailing-side second main girder steel plate 30C has an outer shape defined by a first main surface 301C, a second main surface 302C, a top surface 303C, a bottom surface 304C, an outer end surface 305C, and an inner end surface 306C, and is curved along the circumferential direction of the outer shell shield 4 in a front view, similar to the trailing-side first main girder steel plate 30B. The trailing-side second main girder steel plate 30C has a trailing-side first perforated steel plate dowel 32B provided on the outer end surface 305C, and a trailing-side second perforated steel plate dowel 32C provided on the inner end surface 306C. The first main surface 301C of the trailing side second main girder steel plate 30C is disposed on the inner side of the segment of the trailing shield 6. The second main surface 302C of the trailing-side second main girder steel plate 30C is arranged so as to face the side opposite to the tip portion 6A of the trailing shield 6 when the trailing-side second main girder steel plate 30C is installed inside the segment of the trailing shield 6.

[0088] The trailing-side second main girder steel plate 30C has a trailing-side first perforated steel plate dowel 32B arranged at the outer end located on the outer end face 305C side, and a trailing-side second perforated steel plate dowel 32C arranged at the inner end located on the inner end face 306C side. In addition, the trailing-side first perforated steel plate dowel 32B is rigidly joined to the second main surface 302C by welding or the like, and the trailing-side second perforated steel plate dowel 32C is rigidly joined to the first main surface 301C by welding or the like. In addition, as shown in FIG. 34, the trailing-side first perforated steel plate dowel 32B and the trailing-side second perforated steel plate dowel 32C are joined at a position (height) above the center in the up-down direction of the trailing-side second main girder steel plate 30C. The trailing-side first perforated steel plate dowel 32B and the trailing-side second perforated steel plate dowel 32C provided on the trailing-side second main girder steel plate 30C are similar to those provided on the trailing-side first main girder steel plate 30B.

[0089] Next, the trailing outer periphery side steel shell element 93B will be described. FIG. 35 is a plan view of the trailing outer periphery side steel shell element 93B. The trailing outer periphery side steel shell element 93B is configured to include a second steel shell unit 94B having a trailing side second main girder steel plate 30B and a trailing side second main girder steel plate 30C combined with the second steel shell unit 94B. As shown in FIG. 35, in the trailing outer periphery side steel shell element 93B, the second steel shell unit 94B and the trailing side second main girder steel plate 30C are separated from each other. The second steel shell unit 94B in the trailing outer periphery side steel shell element 93B has a basic structure similar to that of the first steel shell unit 94A. In the second steel shell unit 94B, the components common to the first steel shell unit 94A are denoted by the same reference numerals and detailed descriptions thereof will be omitted.

[0090] The second steel shell unit 94B in the trailing outer periphery steel shell element 93B is configured to include a trailing side edge cutting steel plate 40B having a substantially rectangular plane and a plurality of trailing side first main girder steel plates 30B erected from the trailing side edge cutting steel plate 40B, similar to the first steel shell unit 94A. The second steel shell unit 94B is also configured as a unit connected along the axial direction of the trailing shield 6, similar to the first steel shell unit 94A.

[0091] Fig. 36 is a front view of the second steel shell unit 94B as viewed from the K direction in Fig. 35. Fig. 37 is a side view of the second steel shell unit 94B as viewed from the L direction in Fig. 35. Fig. 38 is a side view of the second steel shell unit 94B as viewed from the M direction in Fig. 35.

[0092] In the second steel shell unit 94B of the trailing outer periphery steel shell element 93B, the bottom surface 304B of the trailing side first main girder steel plate 30B is joined to the main girder holding surface 403C of the trailing side edge cutting steel plate 40B. In the second steel shell unit 94B, the trailing side edge cutting steel plate 40B and the trailing side first main girder steel plate 30B are curved in an arc shape along the circumferential direction of the outer shell shield 4 in a front view. When the second steel shell unit 94B is installed inside the segment of the trailing shield 6, the first side surface 401B of the trailing side edge cutting steel plate 40B faces the tip portion 6A side of the trailing shield 6, the second side surface 405B faces the opposite side to the tip portion 6A of the trailing shield 6, and the edge cutting surface 404B is arranged to face the upper side of the trailing shield 6 (the outer periphery side of the outer shell shield 4). In addition, in the second steel shell unit 94B of the trailing outer peripheral steel shell element 93B, a cutout portion 407 extending along the long side direction of the trailing side edge cutting steel plate 40B is provided on the outer end face 406B side of the trailing side edge cutting steel plate 40B, so that when the second steel shell unit 94B is set in the trailing shield 6, interference between the main girder of the steel segment 61 and the trailing side edge cutting steel plate 40B is suppressed.

[0093] In the second steel shell unit 94B, as in the first steel shell unit 94A, three trailing side first shells are installed. A trailing-side first main girder steel plate 30B is provided, and a trailing-side first perforated steel plate dowel 32B is provided at the outer end of each trailing-side first main girder steel plate 30B, and a trailing-side second perforated steel plate dowel 32C is provided at the inner end of each trailing-side first main girder steel plate 30B. The trailing-side first perforated steel plate dowel 32B and the trailing-side second perforated steel plate dowel 32C are rigidly joined to the second main surface 302B of the trailing-side first main girder steel plate 30B by welding or the like. Also, as shown in Figs. 37 and 38, the trailing-side first perforated steel plate dowel 32B and the trailing-side second perforated steel plate dowel 32C of each trailing-side first main girder steel plate 30B in the second steel shell unit 94B are joined at a position (height) lower than the center in the up-down direction of the trailing-side first main girder steel plate 30B.

[0094] Next, a procedure for installing the trailing inner periphery side steel shell element 93A and the trailing outer periphery side steel shell element 93B configured as described above will be described.

[0095] 39 to 45 are diagrams for explaining the installation state of the trailing inner periphery side steel shell element 93A. FIG. 39 shows a schematic plan view of the first steel shell unit 94A and the trailing side second main girder steel plate 30C in the trailing inner periphery side steel shell element 93A temporarily installed in the outer shell body construction area B21 of the trailing shield 6. FIG. 39 shows a part of the leading inner periphery side steel shell element 91A constructed on the leading shield 5 to which both sides of the trailing shield 6 are connected, specifically, the end area AE1 of the leading inner periphery side steel shell element 91A arranged in the box cutout portion 16. Also, the reference numeral 61A in FIG. 39 is the main girder of the steel segment 61.

[0096] In a state where the first steel shell unit 94A is temporarily installed in the shell construction area B21 of the trailing shield 6, the trailing side edge cutting steel plate 40B is arranged so that the edge cutting surface 404A faces the lower side of the trailing shield 6 (the inner circumference side of the outer shell shield 4). Also, as shown in FIG. 39, a plurality of trailing side second main girder steel plates 30C are arranged in a superimposed state on the main girder holding surface 403C of the trailing side edge cutting steel plate 40B in the first steel shell unit 94A. As shown in FIG. 39, the trailing side second main girder steel plates 30C are arranged in a number corresponding to the trailing side first main girder steel plate 30B in the trailing side edge cutting steel plate 40B. In the temporary installation state shown in FIG. 39, the first main surface 301B of the trailing side first main girder steel plate 30B of the first steel shell unit 94A and the second main surface 302C of the trailing side second main girder steel plate 30C are arranged back to back. In addition, in the temporary installation state, the outer end of each trailing side second main girder steel plate 30C is positioned on the inner end side of the trailing side first main girder steel plate 30B, and the inner end of each trailing side second main girder steel plate 30C is positioned on the outer end side of the trailing side first main girder steel plate 30B.

[0097] Next, from the temporary installation state shown in Fig. 39, the first steel shell unit 94A is slid to one side in the width direction of the trailing shield 6, and the outer end side of the first steel shell unit 94A is inserted into the box cutout portion 16 of one leading shield 5 connected to the trailing shield 6. Specifically, the first main surface 301B and the bottom surface 304B of each trailing side first main girder steel plate 30B in the first steel shell unit 94A are aligned with the second main surface 302A of the leading side main girder steel plate 30A and the main girder holding surface 403A of the leading side edge cutting steel plate 40A, respectively, while the outer end of the trailing side first main girder steel plate 30B is inserted into the gap portion V1 of the leading inner circumference side steel shell element 91A.

[0098] Then, as shown in Fig. 40, the first steel shell unit 94A is positioned and fixed at a first normal position where the trailing side first perforated steel plate dowel 32B attached to the outer end of the trailing side first main girder steel plate 30B faces (vertically overlaps) the leading side perforated steel plate dowel 32A of the leading side main girder steel plate 30A arranged in the box cutout portion 16 of the leading shield 5. Hereinafter, the first steel shell unit 94A is positioned and fixed at the first normal position in a state where the outer end surface 402B of the trailing side edge cutting steel plate 40B is abutted against the end surface 402A of the leading side edge cutting steel plate 40A. Hereinafter, the state where the first steel shell unit 94A has been positioned and fixed at the first normal position is referred to as the "first positioning state".

[0099] Here, the outer end surface 402B of the trailing edge cutting steel plate 40B in the first steel shell unit 94A are arranged at a position retreated inward from the trailing-side first perforated steel plate dowel 32B provided at the outer end of each trailing-side first main girder steel plate 30B. Therefore, each trailing-side first perforated steel plate dowel 32B of the first steel shell unit 94A can be smoothly inserted into the end region AE1 of the leading inner periphery side steel shell element 91A without interfering with the outer end surface 402B of the trailing-side edge cutting steel plate 40B and the end surface 402A of the leading-side edge cutting steel plate 40A. Furthermore, since the trailing-side edge cutting steel plate 40B of the first steel shell unit 94A has a notch 407, when the first steel shell unit 94A is slid laterally from the temporary installation state, the main girder 61A of the steel segment 61 can be received into the notch 407 of the trailing-side edge cutting steel plate 40B. In this way, by receiving the main girder 61A of the steel segment 61 in the cutout portion 407 of the trailing edge cutting steel plate 40B, each trailing first perforated steel plate dowel 32B of the first steel shell unit 94A can be smoothly inserted into the end region AE1 of the leading inner circumference side steel shell element 91A. The cutout portion 407 of each first steel shell unit 94A is designed so that when the first steel shell units 94A are connected along the axial direction of the trailing shield 6, the cutout portion 407 of each first steel shell unit 94A and each main girder 61A of the steel segment 61 are aligned in the axial direction of the shield.

[0100] Furthermore, the leading-side perforated steel plate dowel 32A in the leading inner periphery side steel shell element 91A is installed at a height near the center in the up-down direction of the leading-side main girder steel plate 30A, and the trailing-side first perforated steel plate dowel 32B in the first steel shell unit 94A in the trailing inner periphery side steel shell element 93A is installed at a height below the center in the up-down direction of the trailing-side first main girder steel plate 30B. According to this, when the outer end surface 402B of the trailing-side edge cutting steel plate 40B of the first steel shell unit 94A is butted against the end surface 402A of the leading-side edge cutting steel plate 40A, the leading-side perforated steel plate dowel 32A and the trailing-side first perforated steel plate dowel 32B are in a vertically staggered positional relationship. This allows the trailing first perforated steel sheet dowel 32B in the first steel shell unit 94A to be smoothly inserted into the end region AE1 of the leading inner circumference side steel shell element 91A without interfering with the leading side perforated steel sheet dowel 32A.

[0101] 41 is a diagram showing the positional relationship between the trailing-side first perforated steel plate dowel 32B of the first steel shell unit 94A and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A in the dowel joint region R1 shown in FIG. 40. In the first positioning state, the trailing-side first perforated steel plate dowel 32B of the first steel shell unit 94A and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A are arranged opposite each other with a vertical gap. In the example shown in FIG. 40 and FIG. 41, in the box punching portion 16, the second-stage dowel hole 320 of the leading-side perforated steel plate dowel 32A and the second-stage dowel hole 320 of the trailing-side first perforated steel plate dowel 32B are arranged so as to overlap each other vertically.

[0102] As described above, after the installation of the first steel shell unit 94A in the first normal position is completed, each of the trailing-side second main girder steel plates 30C in the temporarily installed state is sequentially slid to the other side in the width direction of the trailing shield 6, and the outer end side of the trailing-side second main girder steel plate 30C is inserted into the box cutout portion 16 of the other leading shield 5 connected to the trailing shield 6. Specifically, the outer end of the trailing-side second main girder steel plate 30C is inserted into the gap portion V1 of the leading inner circumference side steel shell element 91A while aligning the first main surface 301C and the bottom surface 304C of the trailing-side second main girder steel plate 30C with the second main surface 302A of the leading-side main girder steel plate 30A and the main girder holding surface 403A of the leading-side edge cutting steel plate 40A, respectively.

[0103] Then, as shown in Figure 42, the trailing-side second main girder steel plate 30C is positioned and fixed at the second regular position where the trailing-side first perforated steel plate dowel 32B at the outer end of each trailing-side second main girder steel plate 30C faces (vertically overlaps) the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A arranged in the box cutout portion 16 of the leading shield 5. As shown in Figure 42, when the trailing-side second main girder steel plate 30C is positioned and fixed at the second regular position, The trailing-side second perforated steel plate dowel 32C provided at the inner end is arranged to face the trailing-side second perforated steel plate dowel 32C of each trailing-side first main girder steel plate 30B in the first steel shell unit 94A. Hereinafter, the state in which the trailing-side second main girder steel plate 30C has been positioned and fixed to the second regular position is referred to as the "second positioning state."

[0104] Here, the leading-side perforated steel plate dowel 32A in the leading inner periphery side steel shell element 91A is installed at a height near the center in the vertical direction of the leading-side main girder steel plate 30A, and the trailing-side first perforated steel plate dowel 32B of the trailing-side second main girder steel plate 30C in the trailing inner periphery side steel shell element 93A is installed at a height above the center in the vertical direction of the trailing-side second main girder steel plate 30C. According to this, when the trailing-side second main girder steel plate 30C is moved to the second normal position, the trailing-side first perforated steel plate dowel 32B of the trailing-side second main girder steel plate 30C and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A are in a vertically staggered positional relationship, and it is possible to suppress mutual interference between them. Therefore, the trailing-side second main girder steel plate 30C can be smoothly moved to the second normal position.

[0105] 43 is a diagram showing the positional relationship between the trailing-side first perforated steel plate dowel 32B of the trailing-side second main girder steel plate 30C and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A in the dowel joint region R2 shown in FIG. 42. In the second positioning state, the trailing-side first perforated steel plate dowel 32B of the trailing-side second main girder steel plate 30C and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A are arranged opposite each other with a vertical gap. In the example shown in FIG. 42 and FIG. 43, in the box punching portion 16, the second-stage dowel hole 320 of the leading-side perforated steel plate dowel 32A and the second-stage dowel hole 320 of the trailing-side first perforated steel plate dowel 32B are arranged so as to overlap each other vertically.

[0106] Fig. 44 is a diagram showing the arrangement relationship between the trailing-side second perforated steel plate dowel 32C at the inner end of the trailing-side first main girder steel plate 30B and the inner end of the trailing-side second main girder steel plate 30C in the dowel joint region R3 shown in Fig. 42. Here, the trailing-side second perforated steel plate dowel 32C of the trailing-side first main girder steel plate 30B in the trailing inner circumference side steel shell element 93A is installed on the lower side of the trailing-side first main girder steel plate 30B, and the trailing-side second perforated steel plate dowel 32C of the trailing-side second main girder steel plate 30C is installed on the upper side of the second main girder steel plate 30C.

[0107] Therefore, when the trailing-side second main girder steel plate 30C is moved to the second normal position, the trailing-side second perforated steel plate dowel 32C at the inner end of the trailing-side second main girder steel plate 30C and the trailing-side second perforated steel plate dowel 32C at the inner end of the trailing-side first main girder steel plate 30B are in a vertically staggered positional relationship, which can prevent them from interfering with each other. Therefore, the trailing-side second main girder steel plate 30C can be moved smoothly to the second normal position.

[0108] In the second positioning state, the trailing-side second perforated steel plate dowel 32C provided at the inner end of the trailing-side first main girder steel plate 30B and the trailing-side second perforated steel plate dowel 32C provided at the inner end of the trailing-side second main girder steel plate 30C are arranged opposite each other with a vertical gap. In the example shown in Figures 42 and 44, the second-stage dowel hole 320 in the trailing-side second perforated steel plate dowel 32C provided at the inner end of the trailing-side first main girder steel plate 30B and the second-stage dowel hole 320 in the trailing-side second perforated steel plate dowel 32C provided at the inner end of the trailing-side second main girder steel plate 30C are arranged so as to overlap each other vertically.

[0109] As described above, after the first steel shell unit 94A and the trailing second main girder steel plate 30C of the trailing inner circumference side steel shell element 93A are installed in the first normal position and the second normal position, as shown in Fig. 45, an additional edge cutting steel plate indicated by the reference symbol 20A is joined to the trailing inner circumference side steel shell element 93A. The additional edge cutting steel plate 20A is joined to the boundary portion between the outer shell structure construction area B21 and the outer shell structure external area B22, where the trailing side edge cutting steel plate 40B of the first steel shell unit 94A is provided. The additional edge cutting steel plate 20A is a cutting steel plate for cutting off both regions by blocking the unfinished part. In FIG. 45, the region where the additional edge cutting steel plate 20A is installed is shown by a hatched region. In this manner, the trailing inner circumferential steel element 93A can be constructed in sequence along the axial direction of the trailing shield 6. In this case, the first steel shell units 94A arranged in series along the axial direction of the trailing shield 6 may be joined to each other by, for example, welding or bolting via a splice plate or the like, with the first side surface 401B and the second side surface 405B of the trailing edge cutting steel plate 40B of the first steel shell unit 94A butting against each other. In this manner, the trailing inner circumferential steel element 93A can be constructed in sequence from the tip portion 6A side of the trailing shield 6 toward the starting base 7 side.

[0110] Next, the installation state of the trailing outer circumference side steel shell element 93B will be described with reference to Figures 46 to 50. The installation procedure of the trailing outer circumference side steel shell element 93B is generally the same as that of the trailing inner circumference side steel shell element 93A. Figure 46 is a view of the state in which the second steel shell unit 94B and the trailing side second main girder steel plate 30C in the trailing outer circumference side steel shell element 93B are installed in the first normal position and the second normal position, respectively, viewed from the main girder holding surface 403C side of the trailing side edge cutting steel plate 40B. In the trailing inner circumference steel shell element 93A, the second steel shell unit 94B and the trailing side second main girder steel plate 30C are temporarily installed in the outer shell structure construction area B21 in the trailing shield 6, and then the second steel shell unit 94B is slid to one side in the width direction of the trailing shield 6 to be installed in the first normal position, and the trailing side second main girder steel plate 30C is sequentially slid to the other side of the trailing shield 6 to be installed in the second normal position.

[0111] In addition, in the temporary installation state of the trailing outer circumference side steel shell element 93B, the edge cutting surface 404A of the trailing side edge cutting steel plate 40B in the second steel shell unit 94B is arranged to face the upper side of the trailing shield 6 (the outer circumference side of the outer shell shield 4). Also, in the trailing outer circumference side steel shell element 93B, similar to the construction of the trailing inner circumference side steel shell element 93A, in the temporary installation state, the trailing side second main girder steel plate 30C in the number corresponding to the trailing side first main girder steel plate 30B is temporarily installed on the main girder holding surface 403C side of the trailing side edge cutting steel plate 40B in the second steel shell unit 94B. At this time, the first main surface 301B of the trailing side first main girder steel plate 30B and the second main surface 302C of the trailing side second main girder steel plate 30C of the second steel shell unit 94B are arranged back-to-back, and the outer end of each trailing side second main girder steel plate 30C is arranged on the inner end side of the trailing side first main girder steel plate 30B, and the inner end of each trailing side second main girder steel plate 30C is arranged on the outer end side of the trailing side first main girder steel plate 30B.

[0112] When the second steel shell unit 94B in the temporary installation state is moved to the first regular position, the first main surface 301B and the top surface 303B of each trailing side first main girder steel plate 30B in the second steel shell unit 94B are aligned with the second main surface 302A of the leading side main girder steel plate 30A in the leading outer peripheral side steel shell element 91B and the main girder holding surface 403A of the leading side edge cutting steel plate 40A, respectively, while the outer end of the trailing side first main girder steel plate 30B is inserted into the gap V1 of the leading outer peripheral side steel shell element 91B. Then, the second steel shell unit 94B is positioned and fixed to the first regular position in a state in which the outer end surface 402B of the trailing side edge cutting steel plate 40B in the second steel shell unit 94B is butted against the end surface 402A of the leading side edge cutting steel plate 40A in the leading outer peripheral side steel shell element 91B.

[0113] Here, the outer end surface 402B of the trailing edge cutting steel plate 40B in the second steel shell unit 94B is disposed at a position retreated inward from the trailing first perforated steel plate dowel 32B provided at the outer end of each trailing first main girder steel plate 30B. Therefore, each trailing first perforated steel plate dowel 32B of the second steel shell unit 94B can be smoothly inserted into the end region AE2 of the leading outer peripheral steel shell element 91B without interfering with the outer end surface 402B of the trailing edge cutting steel plate 40B in the second steel shell unit 94B and the end surface 402A of the leading edge cutting steel plate 40A in the leading outer peripheral steel shell element 91B. Furthermore, since the trailing edge cutting steel plate 40B of the second steel shell unit 94B is also provided with a notch portion 407, the second steel shell unit 94B can be inserted into the first normal position. When the second steel shell unit 94B is moved to the position, the main girder 61A of the steel segment 61 can be received in the cutout portion 407. This allows each trailing first perforated steel sheet dowel 32B of the second steel shell unit 94B to be smoothly inserted into the end region AE2 of the leading outer periphery side steel shell element 91B.

[0114] In addition, the leading-side perforated steel plate dowel 32A in the leading outer periphery side steel shell element 91B is installed at a height near the center of the leading-side main girder steel plate 30A, and the trailing-side first perforated steel plate dowel 32B in the second steel shell unit 94B is installed at a lower height of the trailing-side first main girder steel plate 30B. Therefore, when the outer end surface 402B of the trailing-side edge cutting steel plate 40B of the second steel shell unit 94B is butted against the end surface 402A of the leading-side edge cutting steel plate 40A, the leading-side perforated steel plate dowel 32A and the trailing-side first perforated steel plate dowel 32B are in a vertically staggered positional relationship. This allows the trailing first perforated steel sheet dowel 32B in the second steel shell unit 94B to be smoothly inserted into the end region AE2 of the leading outer peripheral steel shell element 91B without interfering with the leading first perforated steel sheet dowel 32A.

[0115] 47 is a diagram showing the positional relationship between the trailing-side first perforated steel plate dowel 32B of the second steel shell unit 94B and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A in the dowel joint region R4 shown in FIG. 46. In the first positioning state, the trailing-side first perforated steel plate dowel 32B of the second steel shell unit 94B and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A are arranged opposite each other with a vertical gap. In the example shown in FIG. 47, in the box punching portion 16, the second-stage dowel hole 320 of the leading-side perforated steel plate dowel 32A and the second-stage dowel hole 320 of the trailing-side first perforated steel plate dowel 32B are arranged so as to overlap each other vertically.

[0116] When each of the trailing-side second main girder steel plates 30C in the temporarily installed state is moved to the second regular position, the first main surface 301C and the top surface 303C of the trailing-side second main girder steel plate 30C are aligned with the second main surface 302A of the leading-side main girder steel plate 30A in the leading outer periphery steel shell element 91B and the main girder holding surface 403A of the leading-side edge cutting steel plate 40A, respectively, while the outer end of the trailing-side second main girder steel plate 30C is inserted into the gap portion V1 of the leading outer periphery steel shell element 91B. Then, the trailing-side second main girder steel plate 30C is positioned and fixed to the second regular position where the trailing-side first perforated steel plate dowel 32B at the outer end of each of the trailing-side second main girder steel plates 30C faces (overlaps vertically) the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A arranged in the box cutout portion 16 of the leading shield 5.

[0117] Here, the leading-side perforated steel plate dowel 32A in the leading outer periphery side steel shell element 91B is installed at a height near the center in the up-down direction of the leading-side main girder steel plate 30A, and the trailing-side first perforated steel plate dowel 32B of the trailing-side second main girder steel plate 30C in the trailing outer periphery side steel shell element 93B is installed at a height above the center in the up-down direction of the trailing-side second main girder steel plate 30C. Therefore, when each trailing-side second main girder steel plate 30C in the trailing outer periphery side steel shell element 93B is moved to the second normal position, the trailing-side first perforated steel plate dowel 32B of the trailing-side second main girder steel plate 30C and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A are in a vertically staggered positional relationship. This allows the trailing first perforated steel plate dowel 32B of the trailing second main girder steel plate 30C in the trailing outer peripheral steel shell element 93B to be smoothly inserted into the end region AE2 of the leading outer peripheral steel shell element 91B without interfering with the leading perforated steel plate dowel 32A of the leading main girder steel plate 30A.

[0118] 48 is a diagram showing the positional relationship between the trailing-side first perforated steel plate dowel 32B of the trailing-side second main girder steel plate 30C and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A in the dowel joint region R5 shown in FIG. The trailing-side first perforated steel plate dowel 32B and the leading-side perforated steel plate dowel 32A of the leading-side main girder steel plate 30A are arranged opposite each other with a gap between them. In the example shown in Fig. 48, in the box punching portion 16, the second row dowel hole 320 of the leading-side perforated steel plate dowel 32A and the second row dowel hole 320 of the trailing-side second perforated steel plate dowel 32C are arranged so as to overlap each other vertically.

[0119] Fig. 49 is a diagram showing the arrangement relationship between the trailing-side second perforated steel plate dowel 32C at the inner end of the trailing-side first main girder steel plate 30B and the inner end of the trailing-side second main girder steel plate 30C in the dowel joint region R6 shown in Fig. 46. Here, the trailing-side second perforated steel plate dowel 32C of the trailing-side first main girder steel plate 30B in the trailing outer periphery-side steel shell element 93B is provided on the lower side of the trailing-side first main girder steel plate 30B, and the trailing-side second perforated steel plate dowel 32C of the trailing-side second main girder steel plate 30C is provided on the upper side of the second main girder steel plate 30C.

[0120] Therefore, when the trailing second main girder steel plate 30C in the trailing outer periphery side steel shell element 93B is moved to the second normal position, the trailing second perforated steel plate dowel 32C at the inner end of the trailing second main girder steel plate 30C and the trailing second perforated steel plate dowel 32C at the inner end of the trailing first main girder steel plate 30B in the second steel shell unit 94B are in a vertically staggered positional relationship, and mutual interference between them can be suppressed. Therefore, the trailing second main girder steel plate 30C in the trailing outer periphery side steel shell element 93B can be smoothly moved to the second normal position.

[0121] When the trailing-side second main girder steel plate 30C of the trailing outer periphery-side steel shell element 93B is installed in the second normal position, the trailing-side second perforated steel plate dowel 32C provided at the inner end of the trailing-side first main girder steel plate 30B and the trailing-side second perforated steel plate dowel 32C provided at the inner end of the trailing-side second main girder steel plate 30C are arranged opposite each other with a vertical gap. In the example shown in Fig. 49, the second-stage dowel hole 320 in the trailing-side second perforated steel plate dowel 32C provided at the inner end of the trailing-side first main girder steel plate 30B and the second-stage dowel hole 320 in the trailing-side second perforated steel plate dowel 32C provided at the inner end of the trailing-side second main girder steel plate 30C are arranged so as to overlap each other vertically.

[0122] As described above, after the second steel shell unit 94B and the trailing second main girder steel plate 30C in the trailing outer periphery side steel shell element 93B are installed in the first normal position and the second normal position, as shown in FIG. 50, the additional edge cutting steel plate 20B is joined to the trailing outer periphery side steel shell element 93B. The additional edge cutting steel plate 20B is an edge cutting steel plate for cutting the boundary between the outer shell body construction area B21 and the outer shell body external area B23, by blocking the part where the trailing side edge cutting steel plate 40B of the second steel shell unit 94B is not provided. In FIG. 50, the area where the additional edge cutting steel plate 20B is installed is illustrated by a hatched area. In this manner, the trailing outer periphery side steel shell element 93B can be constructed sequentially along the axial direction of the trailing shield 6. In this case, the second steel shell units 94B arranged in series along the axial direction of the trailing shield 6 may be joined to each other by, for example, welding or bolting via a splice plate or the like, with the first side surface 401B and the second side surface 405B of the trailing side edge cutting steel plate 40B of the second steel shell units 94B butting against each other. In this manner, the trailing outer peripheral side steel shell elements 93B can be constructed in sequence from the tip portion 6A side of the trailing shield 6 toward the departure base 7 side.

[0123] Fig. 51 is a diagram showing a cross section of a part of the outer shell shield 4 after the trailing inner periphery steel shell element 93A and the trailing outer periphery steel shell element 93B are installed on the trailing shield 6. From this state, the concrete structure 95 and the non-structural elements 67, 68 are constructed in an appropriate order. That is, in the trailing shield 6, similarly to the leading shield 5, the concrete structure 95 and the non-structural elements 67, 68 are constructed according to the location of the trailing shield 6, i.e., the positional relationship with the weight direction. For example, When constructing the trailing shield 6, the outer shell structure external area B22 is located on the lower side in the direction of gravity within the trailing shield 6, the outer shell structure external area B23 is located on the upper side in the direction of gravity, and the outer shell structure construction area B21 is positioned between these.

[0124] In this embodiment, depending on the location where each trailing shield 6 is arranged, the concrete body 95 and the non-structural elements 67, 68 are constructed in order from the lower side to the upper side in the direction of gravity, or in parallel. For example, when the outer shell body external area B22 is located on the lower side in the direction of gravity and the outer shell body external area B23 is located on the upper side in the direction of gravity in the trailing shield 6, first, as shown in FIG. 52, the outer shell body external area B22 located on the lower side in the direction of gravity is filled with liquefied treated soil to construct the non-structural element 67. Then, as shown in FIG. 53, the concrete body 95 is constructed by pouring concrete in the outer shell body construction area B21. After that, the outer shell body external area B23 located on the upper side in the direction of gravity is filled with liquefied treated soil to construct the non-structural element 68. As a result, as shown in FIG. 28, the concrete body 95 and the non-structural elements 67, 68 are constructed in the trailing shield 6.

[0125] In contrast to the above example, in the case of the trailing shield 6 arranged on the bottom side of the outer shell shield 4, the outer shell skeleton external region B22 is located on the upper side in the direction of gravity, the outer shell skeleton external region B23 is located on the lower side in the direction of gravity, and the outer shell skeleton construction region B21 is located between them. In this case, the construction order is reversed from the above example, and first, the non-structural element 58 is constructed in the outer shell skeleton external region B23 located on the lower side in the direction of gravity, and then concrete is poured in the outer shell skeleton construction region B21 to construct the skeleton concrete 95, and finally, the non-structural element 67 is constructed in the outer shell skeleton external region B22 located on the upper side in the direction of gravity. Also, instead of filling the outer shell skeleton external regions B22 and B23 of the trailing shield 6 with liquefied treated soil, concrete may be filled in the outer shell skeleton external regions B22 and B23. That is, the concrete structure 95 may be constructed in the outer regions B22 and B23 of the outer shell structure of the trailing shield 6.

[0126] When concrete is poured in the outer shell construction region B21 of the trailing shield 6, concrete is poured in the region sandwiched between the trailing edge cutting steel plate 40B and the additional edge cutting steel plate 20A in the trailing inner circumferential steel shell element 93A and the additional edge cutting steel plate 20B in the trailing outer circumferential steel shell element 93B. As a result, the trailing main girder steel plates (i.e., the trailing first main girder steel plate 30B and the trailing second main girder steel plate 30C) in each of the trailing inner circumferential steel shell element 93A and the trailing outer circumferential steel shell element 93B are covered with concrete to form an integral structure with the concrete structure 95. In addition, when constructing the concrete structure 95, concrete is also filled in the box-out portions 16 of each leading shield 5 connected to both sides of the trailing shield 6 and in the space formed by removing the cutting elements 56 in the cutting region A1 of the leading shield 5.

[0127] Here, in each of the above-mentioned dowel joint regions R1 to R6, the perforated steel plate dowels arranged opposite to each other are embedded in the concrete structure 95. As a result, the perforated steel plate dowels arranged opposite to each other are joined together via the concrete structure 95. Fig. 54 is a diagram for explaining the joining state between the trailing first perforated steel plate dowel 32B in the trailing first main girder steel plate 30B of the trailing inner circumference side steel shell element 93A (first steel shell unit 94A) and the leading side perforated steel plate dowel 32A in the leading side main girder steel plate 30A of the leading inner circumference side steel shell element 91A in the dowel joint region R1. As described above, the trailing side first perforated steel plate dowel 32B rigidly connected to the end of the trailing side first main girder steel plate 30B and the leading side perforated steel plate dowel 32A rigidly connected to the end of the leading side main girder steel plate 30A are arranged opposite to each other with a gap between them, and these dowels 32A, 32B are integrated in a state where they are embedded in the concrete structure 95. As a result, the leading side perforated steel plate dowel 32A and the trailing side first perforated Stress can be transmitted between the leading side perforated steel plate dowel 32A and the trailing side first perforated steel plate dowel 32B via the structural concrete 95 that integrally covers the leading inner periphery steel shell element 91A and the trailing side first main girder steel plate 30B of the trailing inner periphery steel shell element 93A (first steel shell unit 94A).

[0128] In addition, in Figure 54, the joining state of the leading side perforated steel plate dowel 32A and the trailing side first perforated steel plate dowel 32B in the dowel joint region R1 is explained, but the joining state of the leading side perforated steel plate dowel 32A and the trailing side first perforated steel plate dowel 32B in the other dowel joint regions R2, R4, R5 is also similar, and stress transmission between the dowels is possible via the structural concrete 95.

[0129] 55 is a diagram for explaining the joining state between the trailing-side second perforated steel plate dowel 32C in the trailing-side first main girder steel plate 30B of the trailing inner circumference side steel shell element 93A and the trailing-side second perforated steel plate dowel 32C in the trailing-side second main girder steel plate 30C in the dowel joint region R3. As described above, the trailing-side second perforated steel plate dowel 32C rigidly joined to the inner end of the trailing-side first main girder steel plate 30B and the trailing-side second perforated steel plate dowel 32C rigidly joined to the inner end of the trailing-side second main girder steel plate 30C are arranged opposite to each other with a gap therebetween, and these dowels 32C, 32C are integrated in a state where they are embedded in the concrete structure 95. This enables stress transmission between the dowels 32C, 32C via the concrete structure 95, thereby enabling stress transmission between the trailing first main girder steel plate 30B and the trailing second main girder steel plate 30C in the trailing inner circumference side steel shell element 93A. In addition, although the dowel joint region R3 has been described in Fig. 55, the same is true for the joint state between the trailing second perforated steel plate dowels 32C in the dowel joint region R6, and stress transmission between the dowels is possible via the concrete structure 95.

[0130] In each of the dowel joint regions R1 to R6, the distance between the perforated steel dowels arranged opposite each other is preferably at least (4 / 3) times the maximum aggregate size of the aggregate contained in the concrete structure 95. In addition, the hole diameter of each dowel hole 320 of the perforated steel dowel is preferably at least (4 / 3) times the maximum aggregate size of the aggregate contained in the concrete structure 95. This improves the filling of concrete in each of the dowel joint regions R1 to R6.

[0131] In this manner, the trailing inner periphery steel shell element 93A, the trailing outer periphery steel shell element 93B, and the trailing outer shell body part 9B including the body concrete 95 are constructed inside the trailing shield 6. As a result, inside the outer shell shield 4 in which the leading shield 5 and the trailing shield 6 arranged alternately in an annular shape are connected in a rosary-like manner, as shown in FIG. 56, an annular outer shell ring body 9 formed by the leading outer shell body part 9A and the trailing outer shell body part 9B being integrally constructed is constructed. The outer shell ring body 9 has a ring-shaped (annular) cross section and extends along the axial direction of the outer shell shield 4, so it is a structural body that can be said to be cylindrical. As a result, a roughly cylindrical outer shell lining body 10 as the outer shell of the underground widening section 1 including the outer shell shield 4 and the outer shell ring body 9 is completed (step S13).

[0132] In the outer shell ring skeleton 9 in this embodiment, the inner ends of the trailing side first main girder steel plate 30B and the trailing side second main girder steel plate 30C in the trailing outer shell skeleton portion 9B are joined to each other by integrating the trailing side second perforated steel plate dowels 32C through concrete (structure concrete 95). Also, the outer ends of the trailing side first main girder steel plate 30B in the trailing outer shell skeleton portion 9B and the ends of the leading side main girder steel plate 30A in the leading outer shell skeleton portion 9A are joined to each other by integrating the trailing side first perforated steel plate dowels 32B and the leading side perforated steel plate dowels 32A through concrete (structure concrete 95). Also, in the trailing outer shell skeleton portion 9B, The outer end of the trailing side second main girder steel plate 30C in the leading shell body section 9A and the end of the leading side main girder steel plate 30A in the leading shell body section 9A are joined to each other by integrating the trailing side first perforated steel plate dowel 32B and the leading side perforated steel plate dowel 32A through concrete (body concrete 95).

[0133] Then, around the entire circumference of the outer shell shield 4, both ends of the trailing main girder steel plates (trailing first main girder steel plate 30B and trailing second main girder steel plate 30C) in the leading inner steel shell element 91A of each trailing shield 6 are sequentially joined to the ends of the leading main girder steel plate 30A in the leading inner steel shell element 91A of the leading shield 5 adjacent to the trailing shield 6, and these are connected in a ring shape along the circumferential direction of the outer shell shield 4, forming a ring-shaped inner steel main girder ring 300A (steel main girder ring) that runs along the circumferential direction of the outer shell shield 4 (see Figure 56). Similarly, over the entire circumference of the outer shell shield 4, both ends of the trailing side main girder steel plate (the trailing side first main girder steel plate 30B and the trailing side second main girder steel plate 30C) in the trailing outer periphery side steel shell element 93B of each trailing shield 6 are joined in sequence to the ends of the leading side main girder steel plate 30A in the leading outer periphery side steel shell element 91B of the leading shield 5 adjacent to the trailing shield 6, and these are connected in a ring shape along the circumferential direction of the outer shell shield 4, forming a ring-shaped outer periphery side steel main girder ring 300B (steel main girder ring) along the circumferential direction of the outer shell shield 4 (see FIG. 56). As a result, stress can be transmitted through each steel main girder ring 300A, 300B over the entire circumference of the outer shell shield 4 (outer shell ring body 9). Hereinafter, the leading side main girder steel plate 30A, the trailing side first main girder steel plate 30B, and the trailing side second main girder steel plate 30C that form the annular steel main girder ring may be collectively referred to simply as "main girder steel plates 30." Also, the first to third perforated steel plate dowels 32A, 32B, 32C arranged at the ends of the main girder steel plate 30 may be collectively referred to simply as "perforated steel plate dowels 32."

[0134] When the outer shell ring body 9 is constructed inside the outer shell shield 4 as described above, next, in step S14, the frozen soils 41, 42 formed on the outer circumferential side and the inner circumferential side of the outer shell shield 4 are thawed.

[0135] Next, in step S15, as shown in Figs. 57 and 58, etc., frozen soil 43 is created on the hem of the outer shell shield 4 on the arrival point side (opposite the starting base 7).

[0136] Next, in step S16, as shown in FIG. 58, the inside of the outer shell shield 4 is excavated. For example, the excavation inside the outer shell shield 4 is performed in a plurality of steps from the upper side of the outer shell shield 4 so as to form a staircase shape. The excavation inside the outer shell shield 4 can be performed by the existing bench cut method. In addition, in the hem part on the opposite side to the starting base 7, concrete is poured in parallel with the excavation work to construct the hem wall 44. That is, concrete is poured in a plurality of steps from the upper side of the outer shell shield 4 to construct the hem wall 44. The hem wall 44 can be constructed by the existing reverse winding method. When the construction of the hem wall 44 is completed, the frozen soil 43 in the hem part is thawed. In addition, a fireproof panel 83 is installed on the steel segment on the inner side of the outer shell shield 4 according to the progress of the internal excavation of the outer shell shield 4. In addition, the segments of the main line shield 2 are removed, and the deck 81 and the internal structure 82 are constructed. This completes the construction of the underground widening section 1 as shown in Fig. 2 (step S17). In this embodiment, steps S05, S06, S10, and S11 for constructing the outer shell shield 4 in the outer shell lining structure 10 correspond to the outer shell shield construction process in the present invention. Also, steps S07 and S12 for forming an outer shell ring body inside the outer shell shield 4 correspond to the outer shell ring body construction process in the present invention.

[0137] <Effects> In the construction method of the outer shell lining 10 in the underground widening section 1 (large cross-section tunnel) described above, the segments of the multiple leading shield 5 and trailing shield 6 (small cross-section shield tunnel) arranged side by side underground are connected in a rosary shape to form a ring-shaped outer shell shield. The method includes a shell shield construction step of forming an outer shield 4, and a shell ring skeleton construction step of forming an outer ring skeleton 9 including annular steel main girder rings 300A, 300B extending along the circumferential direction of the outer shield 4 inside the outer shield 4 and skeleton concrete 92, 95 covering the steel main girder rings 300A, 300B. The steel main girder rings 300A, 300B are formed by a plurality of main girder steel plates 30 that are jointed to each other via perforated steel dowels 32 rigidly joined to both ends in the longitudinal direction, and in the shell ring skeleton construction step, concrete is poured into the outer shield 4 so that the perforated steel dowels 32 arranged at the ends of the main girder steel plates 30 to be joined to each other are arranged facing each other with a gap between them, and the perforated steel dowels 32 are embedded in the concrete, and the main girder steel plates 30 are joined to each other via the concrete. This allows the main girder steel plates 30 forming the steel main girder rings 300A, 300B to be joined together without directly welding or bolting them together, making it extremely easy to install.

[0138] In particular, in this embodiment, in the outer shell ring skeleton construction process, a leading shield machine is launched from a launch base 7 constructed underground, and multiple leading shields 5 with cuttable cutting segments 52 are constructed at intervals from each other, and then a trailing shield machine is launched from the launch base 7, and multiple trailing shields 6 are constructed between adjacent leading shields 5 while cutting parts of the leading shields 5, thereby connecting the alternating leading shields 5 and trailing shields 6 like beads, and cutting open segments of the trailing shields 6 located at the boundaries with the leading shields 5 to form the outer shell shield 4. In contrast, according to the joining structure between the main girder steel plates 30 in this embodiment, the main girder steel plates 30 can be joined together in a state in which the perforated steel plate dowels 32 in a pair of main girder steel plates 30 to be joined are arranged opposite each other and at intervals, so that even if there is some error in the construction positions of the leading shields 5 and the trailing shields 6, the error in the construction positions can be absorbed and the main girder steel plates 30 can be joined together. Therefore, even if there is a slight error in the construction position of the leading shield 5 or the trailing shield 6, it will not result in the main girder steel plates 30 being unable to be joined together or in the need to rework the joining work, which would require a great deal of effort and time, and the construction is extremely easy.

[0139] Furthermore, the steel main girder rings 300A, 300B in the outer shell ring body 9 include a leading side main girder steel plate 30A that is horizontally laid within the leading shield 5 so as to follow the circumferential direction of the outer shell shield 4, and trailing side main girder steel plates 30B, 30C that are horizontally laid within the trailing shield 6 so as to follow the circumferential direction of the outer shell shield 4, and in the outer shell ring body construction process, the leading side perforated steel plate dowel 32A arranged at the end of the leading side main girder steel plate 30A and the second perforated steel plate dowel 32B (trailing side perforated steel plate dowel) arranged at the end of the trailing side main girder steel plates 30B, 30C are joined together via concrete. According to this, the leading side main girder steel plate 30A, which is horizontally suspended on the leading shield 5, and the trailing side main girder steel plates 30B, 30C, which are horizontally suspended on the trailing shield 6, can be sequentially joined to preferably construct annular steel main girder rings 300A, 300B.

[0140] In the present embodiment, in the outer shell ring body construction process, before constructing the trailing shield 6, a leading outer shell body portion 9A that will become part of the outer shell ring body 9 is constructed in advance in the leading shield 5 in the outer shell body construction area A21 that does not include the cutting area to be cut by the trailing shield machine, and concrete is box-punched in the end areas AE1 and AE2 including the leading side perforated steel plate dowel 32A in the leading side main girder steel plate 30A during construction of the leading outer shell body portion 9A. In this way, a box cutout portion 16 is formed in the trailing shield 6, and after the trailing shield 6 is constructed, the trailing first perforated steel plate dowel 32B (trailing perforated steel plate dowel) in the trailing main girder steel plates 30B, 30C is inserted into the box cutout portion 16, and concrete is filled in the trailing shield 6 and in the box cutout portion 16, thereby integrally joining the ends of the leading side main girder steel plate 30A and the trailing side main girder steel plates 30B, 30C and constructing the trailing outer shell body portion 9B in the trailing shield 6. In this way, the leading outer shell body portion 9A is constructed in the leading shield 5 beforehand, before the trailing shield 6 is constructed. After constructing the trailing outer hull body section 9B within the trailing shield 6, the leading side main girder steel plate 30A and the trailing side main girder steel plates 30B, 30C can be joined together, making it possible to construct the outer hull covering body 10 with good workability.

[0141] Next, a modified example of the construction method of the shell lining body 10 according to the first embodiment will be described. Fig. 59 is a diagram for explaining modified example 1 of the first embodiment. Fig. 59 is a diagram for explaining the joining state of the trailing first main girder steel plate 30B of the trailing inner periphery side steel shell element 93A (first steel shell unit 94A) and the leading main girder steel plate 30A of the leading inner periphery side steel shell element 91A in the dowel joint region R1. As shown in Fig. 59, in modified example 1, the skeleton concrete 95 is poured in the shell shield 4 in a state where the rod-shaped or plate-shaped reinforcing steel materials 21A, 21B are inserted into the dowel holes 320 of the leading side perforated steel plate dowel 32A and the trailing side first perforated steel plate dowel 32B.

[0142] Here, the reinforcing iron material 21A is a reinforcing iron material arranged so as to straddle the dowel hole 320 of one perforated steel plate dowel 32 and the dowel hole 320 of the other perforated steel plate dowel 32 arranged opposite each other, and in the example shown in Fig. 59, the reinforcing iron material 21A is arranged straddling the second row dowel hole 320 of the leading side perforated steel plate dowel 32A and the second row dowel hole 320 of the trailing side first perforated steel plate dowel 32B. Also, the reinforcing iron material 21B is a reinforcing iron material arranged so as to solely pass through the first row dowel hole 320 of the leading side perforated steel plate dowel 32A or the first row dowel hole 320 of the trailing side first perforated steel plate dowel 32B. As in this modification, pouring the concrete structure 95 with the reinforcing bars 21A, 21B inserted through the dowel holes 320 of the perforated steel dowel 32 can suitably reinforce the concrete between the opposing perforated steel dowels 32, thereby increasing the joint strength in the dowel joint region R1. Note that, although the dowel joint region R1 has been described as an example in Fig. 59, the reinforcing steel members 21A, 21B according to this modification can be applied to the other dowel joint regions R2 to R6.

[0143] In this modification, the hole diameter of the dowel hole 320 in each perforated steel plate dowel is preferably set so that the dimension obtained by subtracting the diameter of the reinforcing iron materials 21A, 21B from the hole diameter of the dowel hole 320 is at least (4 / 3) times the maximum aggregate dimension of the aggregate contained in the concrete structure 95. This improves the filling of concrete in each dowel joint region R1 to R6.

[0144] FIG. 60 is a diagram for explaining the second modified example of the first embodiment. FIG. 60 is a plan view of the dowel joint region R3. Reference numeral 22 shown in FIG. 60 is a constraining steel plate that constrains the dowel joint region R3. The constraining steel plate 22 is a steel plate having a rectangular plane, and is welded to the top surface 303B of the trailing side first main girder steel plate 30B and the top surface 303C of the trailing side second main girder steel plate 30C so as to cover the upper part of the dowel joint region R3. A concrete filling port 220 is opened in the plate thickness direction in the constraining steel plate 22, so that concrete can be filled into the dowel joint region R3 through the concrete filling port 220. The shape, size, position, number, range, etc. of the concrete filling port 220 in the constraining steel plate 22 can be changed. By installing the restraining steel plate 22 in the dowel joint region R3 as in this modified example, the concrete filled in the dowel joint region R3 can be restrained from all sides by the trailing edge cutting steel plate 40B, the trailing first main girder steel plate 30B, the trailing second main girder steel plate 30C, and the restraining steel plate 22 in the first steel shell unit 94A. In this way, by increasing the degree of restraint of the concrete filled in the dowel joint region R3, cracks are less likely to occur in the concrete in the dowel joint region R3, and the joint strength of the dowel joint region R3 can be further increased. Note that, although the case where the restraining steel plate 22 is applied to the dowel joint region R3 has been described as an example in FIG. 60, the restraining steel plate 22 can be applied to the other dowel joint regions R1, R2, R4 to R6.

[0145] FIG. 61 is a diagram showing a modified example of the restraining steel plate 22. The restraining steel plate 22 shown in FIG. 61 has a concrete filling port 220 provided so as to cross the restraining steel plate 22, and the restraining steel plate 22 is divided into two, a first restraining piece 22A and a second restraining piece 22B, by the concrete filling port 220. The first restraining piece 22A and the second restraining piece 22B are welded to, for example, the top surface 303B of the trailing side first main girder steel plate 30B. The restraining steel plate 22 in this modified example has a lower concrete restraining effect than the restraining steel plate 22 according to the modified example 2 described in FIG. 60 because it is divided into the first restraining piece 22A and the second restraining piece 22B by the concrete filling port 220. However, it can be welded to the top surface 303B of the trailing side first main girder steel plate 30B in advance, rather than after the trailing shield 6 is installed at the specified position. Therefore, the number of steps required for constructing the outer shell ring body 9 in the outer shell covering structure 10 can be reduced, and the workability can be improved.

[0146] In addition, various embodiments can be adopted for the construction method of the underground widening portion 1 according to the present invention. For example, in the above embodiment, the starting shaft 11 is constructed by excavating the ground surface, but of course, this is not limited to this. For example, the ramp shield 3 or a segment of the main line shield 2 may be cut open to construct an underground shaft, and the starting base 7 may be constructed by the underground shaft. In the above embodiment, the starting base 7 is constructed on the branching and merging portion side where the main line shield 2 and the ramp shield 3 are connected, but the starting base 7 may be provided on the single side of the main line shield 2. In the above embodiment, the case where one perforated steel plate dowel 32 is arranged on each end of the main girder steel plate 30 (leading side main girder steel plate 30A, trailing side main girder steel plates 30B, 30C) forming the steel main girder rings 300A, 300B in the outer shell ring body 9 has been described as an example, but the number of perforated steel plate dowels 32 arranged on each end is not particularly limited. For example, a plurality of perforated steel plate dowels 32 (for example, two stages) may be provided at each end of the main girder steel plates 30 (leading side main girder steel plate 30A, trailing side main girder steel plates 30B, 30C).

[0147] <Embodiment 2> Next, a description will be given of embodiment 2. The following description will focus on the differences from the above-described embodiments and their modifications. In addition, the same reference symbols are used to designate components common to the above-described embodiments and their modifications, and detailed descriptions thereof will be omitted.

[0148] FIG. 62 is a diagram showing the outer shell ring body 9 of the outer shell shield 4 according to the second embodiment. FIG. 63 is a diagram showing a part of the outer shell ring body 9 according to the second embodiment. As in the first embodiment, the annular outer shell ring body 9 is constructed by integrating the leading outer shell body part 9A and the trailing outer shell body part 9B. In addition, the reference characters S-1 to S-15 in FIG. 62 indicate the leading shield 5 by serial numbers. The reference characters K-1 to K-15 indicate the trailing shield 6 by serial numbers. In this embodiment, the number of leading shields 5 and trailing shields 6 forming the outer shell shield 4 is different from that in the first embodiment, but as described above, the number of leading shields 5 and trailing shields 6 forming the outer shell shield 4 is not particularly limited. In addition, in FIG. 62 and FIG. 63, illustration of the structural concrete 92, 95 and various non-structural elements in the outer shell shield 4 is omitted. Along the circumferential direction of the outer shell ring body 9, the ends of the leading inner circumferential side steel shell element 91C and the leading outer circumferential side steel shell element 91D in the leading shield 5 are sequentially and integrally connected to the ends of the trailing inner circumferential side steel shell element 93C and the trailing outer circumferential side steel shell element 93D in the trailing shield 6, respectively, to construct an annular outer shell ring body 9. In addition, in this embodiment, as in the above-mentioned embodiment 1, the outer shell ring body 9 is continuously installed along the shield axial direction from the tip side to the starting base side of the shield. Also, the reference numerals 99A and 99B shown in FIG. 63 are shear reinforcement steel materials. The shear reinforcement steel materials 99A and 99B extend in the radial direction of the outer shell ring body 9 and are arranged at a predetermined pitch around the entire circumference of the outer shell ring body 9.

[0149] In this embodiment, the basic construction procedure in the underground widening section 1 is the same as that in the above-mentioned embodiment 1. In embodiment 2, the configurations of the leading inner circumference side steel shell element 91C and the leading outer circumference side steel shell element 91D in the leading outer shell body section 9A, and the trailing inner circumference side steel shell element 93C and the trailing outer circumference side steel shell element 93D in the trailing outer shell body section 9B are different from those in embodiment 1. The following mainly describes the detailed structure of each of these steel shell elements.

[0150] Fig. 64 is a diagram for explaining the connection relationship between the leading inner periphery side steel-shell element 91C and the trailing inner periphery side steel-shell element 93C according to embodiment 2. Fig. 65 is a diagram for explaining the connection relationship between the leading outer periphery side steel-shell element 91D and the trailing outer periphery side steel-shell element 93D according to embodiment 2.

[0151] As shown in FIG. 64, a leading-side perforated steel plate dowel 32D is provided at both ends of the leading inner circumference side steel shell element 91C in the longitudinal direction. On the other hand, the trailing inner circumference side steel shell element 93C includes a trailing first steel shell unit 94C and a trailing second steel shell unit 94D that are joined together via a splice plate. The trailing first steel shell unit 94C and the trailing second steel shell unit 94D form the trailing inner circumference side steel shell element 93C by joining together the inner end regions formed on one side of the longitudinal direction via a splice steel plate. In addition, a trailing-side perforated steel plate dowel 32E is provided in the outer end region formed as the other end of the trailing first steel shell unit 94C and the trailing second steel shell unit 94D. The trailing first steel shell unit 94C and the trailing second steel shell unit 94D are joined to the leading side perforated steel shell dowel 32E of the adjacent leading inner periphery steel shell element 91C via concrete. In this manner, the leading inner periphery steel shell element 91C and the trailing inner periphery steel shell element 93C are alternately connected along the circumferential direction of the outer shell shield 4 (outer shell ring body 9).

[0152] As shown in FIG. 65, a leading-side perforated steel plate dowel 32D is provided at both ends of the leading outer peripheral side steel shell element 91D in the longitudinal direction. On the other hand, the trailing outer peripheral side steel shell element 93D includes a trailing first steel shell unit 94E and a trailing second steel shell unit 94F that are joined together via a splice plate. The trailing first steel shell unit 94E and the trailing second steel shell unit 94F form the trailing outer peripheral side steel shell element 93D by joining together the inner end regions formed on one side of the longitudinal direction via a splice steel plate. In addition, a trailing-side perforated steel plate dowel 32E is provided in the outer end region formed as the other end of the trailing first steel shell unit 94E and the trailing second steel shell unit 94F. The trailing first steel shell unit 94E and the trailing second steel shell unit 94F are joined to the leading side perforated steel plate dowel 32E of the adjacent leading outer peripheral side steel shell element 91D via concrete. In this manner, the leading outer peripheral side steel shell element 91D and the trailing outer peripheral side steel shell element 93D are alternately connected along the circumferential direction of the outer shell shield 4 (outer shell ring body 9).

[0153] FIG. 66 is a diagram for explaining a leading inner periphery side steel shell element 91C according to the embodiment 2. (a) is a plan view of the leading inner periphery side steel shell element 91C. (b) is a plan view of the leading inner periphery side steel shell element 91C in the N direction in (a). 1C is a front view of the leading inner periphery side steel shell element 91C as viewed from the O direction in FIG.

[0154] The leading inner circumference side steel shell element 91C is a unit including a leading side edge cutting steel plate 40A and a plurality of leading side main girder steel plates 30D erected from this leading side edge cutting steel plate 40A. In this embodiment, the leading inner circumference side steel shell element 91C is connected along the axial direction of the leading shield 5, so as to extend from the tip 5A (see FIG. 9) of the leading shield 5 to the starting base 7. The basic configuration of the leading side edge cutting steel plate 40A is the same as in embodiment 1. When the leading side edge cutting steel plate 40A is installed in the outer shell structure construction area A21 (see FIG. 21) of the leading shield 5, the long side direction is arranged along the width direction of the leading shield 5, and the leading side edge cutting steel plate 4 The leading side edge cutting steel plate 40A is arranged so that the short side direction of the leading side edge cutting steel plate 40A is along the axial direction of the leading shield 5. Furthermore, the leading side edge cutting steel plate 40A is arranged so that the first side surface 401A faces the tip portion 5A of the leading shield 5. Furthermore, similar to embodiment 1, the edge cutting surface 404A of the leading side edge cutting steel plate 40A is arranged so as to face the lower side of the leading shield 5 (the inner side of the outer shell shield 4). Note that the leading side edge cutting steel plate 40A of the leading inner side steel shell element 91C is curved in an arc shape in front view so as to follow the circumferential direction of the outer shell shield 4 to be constructed.

[0155] On the girder support surface 403A of the leading-side edge cutting steel plate 40A, two leading-side main girder steel plates 30D are erected in parallel with a gap therebetween and extending along the long side direction of the leading-side edge cutting steel plate 40A. The leading-side main girder steel plate 30D is curved along the circumferential direction of the outer shell shield 4 to be constructed in a front view, similar to the leading-side edge cutting steel plate 40A. In addition, the number of leading-side main girder steel plates 30D erected from the leading-side edge cutting steel plate 40A is not particularly limited. In addition, the longitudinal length of each leading-side main girder steel plate 30D is equal to the long side dimension of the leading-side edge cutting steel plate 40A, and each end face 305A in the longitudinal direction of each leading-side main girder steel plate 30D is aligned with the end face 402A of the leading-side edge cutting steel plate 40A.

[0156] Leading side perforated steel plate dowels 32D are rigidly joined by welding or the like to both end regions in the longitudinal direction of the leading side main girder steel plate 30D. Two leading side perforated steel plate dowels 32D are provided in each end region of the leading side main girder steel plate 30D, one of which is vertically erected from the first main surface 301A toward the side, and the other is vertically erected from the second main surface 302A toward the side. In other words, each leading side perforated steel plate dowel 32D of the leading side main girder steel plate 30D protrudes from the first main surface 301A and the second main surface 302A in the end region of the leading side main girder steel plate 30D toward the width direction of the leading inner periphery side steel shell element 91A (leading side edge cutting steel plate 40A) and is held in a position approximately parallel to the leading side edge cutting steel plate 40A. A plurality of dowel holes 320 are drilled in the leading side perforated steel plate dowel 32D so as to penetrate the leading side perforated steel plate dowel 32D in the thickness direction. The leading side perforated steel plate dowel 32D has a rectangular planar shape defined by a pair of long sides and a pair of short sides, and one long side is connected along the first main surface 301A or the second main surface 302A of the leading side main girder steel plate 30D. In addition, the leading side perforated steel plate dowel 32D has four dowel holes 320 arranged along the long side direction. However, the number, shape, size, and arrangement pattern of the dowel holes 320 in the leading side perforated steel plate dowel 32D are not particularly limited. In addition, each leading side perforated steel plate dowel 32D is provided at a position (height) near the center in the up-down direction (height direction) of the leading side main girder steel plate 30D.

[0157] FIG. 67 is a partial enlarged view showing one end region in the longitudinal direction of the leading inner periphery side steel shell element 91C according to the second embodiment (the right end in the figure in the example in FIG. 65(a)). An end plate (bearing steel plate) 34 is joined to each end face 305A in the longitudinal direction of the leading side main girder steel plate 30D. The end plate 34 is, for example, a square or rectangular flat steel plate, and is joined to the end face 305A of the leading side main girder steel plate 30D by welding or the like. The end plate 34 is disposed perpendicular to the longitudinal direction of the leading side main girder steel plate 30D. In addition, the end plate 34 is provided with an opening 341 penetrating the end plate 34 in the thickness direction in order to improve the filling property of concrete when concrete is poured. The shape, position, size, etc. of the opening 341 in the end plate 34 are not particularly limited. In the example shown in FIG. 66, a circular opening 341 is provided in the vicinity of the center of the end plate 34.

[0158] In addition, a restraining steel plate 96 having a rectangular plane is provided in the end region of the leading-side main girder steel plate 30D so as to cover the upper part of the leading-side perforated steel plate dowel 32D. The restraining steel plate 96 is arranged across the top surface 303A of each leading-side main girder steel plate 30D and is joined to the end region of each leading-side main girder steel plate 30D by, for example, welding. In addition, as shown in Figures 66 and 67, the restraining steel plate 96 is arranged opposite the end region in the long side direction of the leading-side edge cutting steel plate 40A. The portion corresponding to the restraining steel plate 96, located in the end region of the leading-side edge cutting steel plate 40A, is referred to as the "restraint steel plate portion 408". In the leading inner periphery side steel shell element 91C, the region sandwiched between the restraint steel plate 96 and the restraint steel plate portion 408 is formed as a dowel joint region, and the leading side perforated steel plate dowel 32D is arranged in this dowel joint region. Furthermore, in the restraint steel plate 96, a shear stop steel material 962 for improving adhesion with concrete is fixed by welding or the like to a surface 961 on the opposite side to the surface facing the dowel joint region (the main girder holding surface 403A of the leading side edge cutting steel plate 40A). The shear stop steel material 962 extends along the force distribution direction, i.e., along a direction perpendicular to the longitudinal direction of the leading side main girder steel plate 30D. However, the shape, number, arrangement pattern, etc. of the shear stop steel material 962 are not particularly limited. Also, the reference numeral 963 shown in FIG. 66 and FIG. 67 denotes a shear reinforcement steel material holding portion for holding the shear reinforcement steel material 99. As shown in FIG. 66(c), the shear reinforcement steel holding portions 963 are provided at positions overlapping with the leading-side main girder steel plates 30D in the up-down direction.

[0159] Here, the portion of the leading-side main girder steel plate 30D excluding the end region (joint region) where the leading-side perforated steel plate dowel 32D is provided is referred to as the "general steel material portion 307". The general steel material portion 307 of the leading-side main girder steel plate 30D is provided with anti-slip steel material 308. The shape, number, arrangement pattern, etc. of the anti-slip steel material 308 are not particularly limited, but in the example shown in FIG. 66, a plurality of anti-slip steel materials 308 are provided at intervals along the longitudinal direction of the general steel material portion 307. The arrangement intervals of the anti-slip steel materials 308 along the longitudinal direction of the general steel material portion 307 may or may not be constant. In addition, the anti-slip steel material 308 is formed of, for example, a flat plate-shaped or strip-shaped steel material, and is provided in the vertical direction (from the lower end to the upper end) of the general steel material portion 307 in the leading-side main girder steel plate 30D. Of course, such an installation mode of the anti-slip steel material 308 is one example. For example, the anti-slip steel material 308 may extend only in a part of the height direction from the lower end to the upper end of the general steel material part 307 of the leading side main girder steel plate 30D. Also, instead of arranging the anti-slip steel material 308 in a line, small pieces of steel plate may be arranged in a dotted shape. For example, the anti-slip steel material 308 is provided on both the first main surface 301A and the second main surface 302A of the general steel material part 307. In the illustrated example, the anti-slip steel material 308 is joined by welding or the like to the same positions on the first main surface 301A side and the second main surface 302A side of the general steel material part 307. However, the anti-slip steel material 308 may be provided only on either one of the first main surface 301A and the second main surface 302A of the general steel material part 307.

[0160] Also, the reference numeral 97 in FIG. 66 denotes a distribution steel material. A plurality of distribution steel materials 97 are arranged at regular intervals in the long side direction of the leading inner circumference side steel shell element 91C. However, the interval between the distribution steel materials 97 is not particularly limited. As shown in FIG. 66, a notch 309 is formed along the longitudinal direction at the lower end of the general steel material portion 307 of the leading side main girder steel plate 30D, and a gap is formed between the bottom surface 304A of the general steel material portion 307 and the main girder holding surface 403A of the leading side edge cutting steel plate 40A to avoid interference with the distribution steel material 97. Each distribution steel material 97 is joined to the bottom surface 304A of the general steel material portion 307 by welding or the like so as to extend along the force distribution direction, i.e., a direction perpendicular to the longitudinal direction of the leading side main girder steel plate 30D. The force distribution steel material 97 is provided with one end protruding outward a predetermined distance from the first side surface 401A of the leading-side edge cutting steel plate 40A, and the other end set back inward a predetermined distance from the second side surface 405A of the leading-side edge cutting steel plate 40A. The protruding dimension of the force distribution steel material 97 from the first side surface 401A and the setback dimension from the second side surface 405A are designed to be equal. Also, reference numeral 409 shown in FIG. 66 denotes a concrete inlet.

[0161] Next, the details of the trailing first steel-shell unit 94C and the trailing second steel-shell unit 94D in the trailing inner circumference side steel-shell element 93C will be described. FIG. 68 is a diagram for explaining the trailing first steel-shell unit 94C of the trailing inner circumference side steel-shell element 93C according to the second embodiment. (a) is a plan view of the trailing first steel-shell unit 94C. (b) is a front view of the trailing first steel-shell unit 94C as viewed from the P direction in (a). FIG. 69 is a diagram for explaining the trailing first steel-shell unit 94C of the trailing inner circumference side steel-shell element 93C according to the second embodiment. 1A and 1B are diagrams illustrating the trailing second steel shell unit 94D of the shell element 93C, in which (a) is a plan view of the trailing second steel shell unit 94D, and (b) is a front view of the trailing second steel shell unit 94D as viewed from the Q direction in (a).

[0162] The trailing first steel shell unit 94C includes a trailing edge cutting steel plate 40B having a substantially rectangular plane and a plurality of trailing main girder steel plates 30E erected from the trailing edge cutting steel plate 40B. Reference numerals 401B and 405B denote a first side surface and a second side surface extending along the long side direction of the trailing edge cutting steel plate 40B, and reference numerals 402B and 406B denote an outer end surface and an inner end surface extending along the short side direction of the trailing edge cutting steel plate 40B. Reference numeral 403B denotes a main girder holding surface of the trailing edge cutting steel plate 40B, and in the example shown in FIG. 68, two trailing main girder steel plates 30E are integrally held by the main girder holding surface 403B. Reference numeral 404B denotes a cutting surface located on the opposite side of the main girder holding surface 403B in the trailing edge cutting steel plate 40B. Further, reference numeral 407 denotes a cutout provided on the outer end surface 406B side of the trailing side edge cutting steel plate 40B. The cutout 407 is formed from the outer end surface 406B of the trailing side edge cutting steel plate 40B along the long side direction of the trailing side edge cutting steel plate 40B. The cutout 407 of the trailing side edge cutting steel plate 40B is an opening for preventing interference between the main girder of the steel segment 61 and the trailing side edge cutting steel plate 40B when the trailing first steel shell unit 94C is installed on the trailing shield 6.

[0163] The first side surface 401B of the trailing side edge cutting steel plate 40B is arranged so as to face the tip 6A side of the trailing shield 6 when the trailing first steel shell unit 94C is installed inside the segment of the trailing shield 6. On the other hand, the second side surface 405B of the trailing side edge cutting steel plate 40B is arranged so as to face the opposite side to the tip 6A of the trailing shield 6, that is, the departure base side, when the trailing first steel shell unit 94C is installed inside the segment of the trailing shield 6. In addition, the edge cutting surface 404B of the trailing side edge cutting steel plate 40B is arranged so as to face the lower side of the trailing shield 6 (the inner peripheral side of the outer shell shield 4) when the trailing first steel shell unit 94C is installed inside the segment of the trailing shield 6. In addition, the trailing side edge cutting steel plate 40B is curved in an arc shape along the circumferential direction of the outer shell shield 4 in a front view.

[0164] The trailing side main girder steel plate 30E is a structural steel plate whose outer shape is defined by a first main surface 301B, a second main surface 302B, a top surface 303B, a bottom surface 304B, an outer end surface 305B, and an inner end surface 306B. The trailing side main girder steel plate 30E is erected from the main girder holding surface 403B side of the trailing side edge cutting steel plate 40B so as to extend along the long side direction of the trailing side edge cutting steel plate 40B. The trailing side main girder steel plate 30E is curved along the circumferential direction of the outer shell shield 4 in the front view, similar to the trailing side edge cutting steel plate 40B. The first main surface 301B of the trailing side main girder steel plate 30E is arranged so as to face the tip portion 6A side of the trailing shield 6 when installed inside the segment of the trailing shield 6. The second principal surface 302B of the trailing side main girder steel plate 30E is positioned so that, when installed inside the segment of the trailing shield 6, it faces the side opposite the tip 6A of the trailing shield 6, i.e., toward the starting base.

[0165] As shown in FIG. 68, the two trailing-side main girder steel plates 30E erected from the trailing-side edge cutting steel plate 40B are arranged parallel to each other with a gap therebetween. Of the trailing-side main girder steel plate 30E, the end region located on the outer end surface 305B side is called the outer end region, and the end region located on the inner end surface 306B side is called the inner end region. A trailing-side perforated steel plate dowel 32E is provided at the outer end of the trailing-side main girder steel plate 30E, and a joining bolt hole BH is provided at the inner end of the trailing-side main girder steel plate 30E. The joining bolt hole BH is a bolt hole for inserting a bolt for joining a splice plate.

[0166] The reference numeral 97 in the figure denotes a distribution steel member extending in one direction in a band shape. The distribution steel members 97 are arranged at regular intervals in the long side direction of the trailing side edge cutting steel plate 40B. However, the interval between the distribution steel members 97 is not particularly limited. Each distribution steel member 97 is arranged in the force distribution direction, i.e., the trailing side main girder steel plate 30E. The trailing-side main girder steel plates 30E are arranged to extend along a direction perpendicular to the longitudinal direction of the trailing-side edge cutting steel plate 40B, and are fixed to the main girder support surface 403B of the trailing-side edge cutting steel plate 40B by welding or the like. Each trailing-side main girder steel plate 30E is joined integrally to the trailing-side edge cutting steel plate 40B via each of the force distribution steel materials 97 by, for example, welding it to each of the force distribution steel materials 97 with the bottom surface 304B abutting against each of the force distribution steel materials 97. Therefore, as shown in FIG. 68, a gap equivalent to the thickness of the force distribution steel material 97 is formed between the bottom surface 304B of each trailing-side main girder steel plate 30E and the main girder support surface 403B of the trailing-side edge cutting steel plate 40B. 68, the longitudinal dimension of the trailing-side main girder steel plate 30E is longer than the long side dimension of the trailing-side edge cutting steel plate 40B, and the trailing-side perforated steel plate dowel 32E provided in the outer end region of the trailing-side main girder steel plate 30E is arranged so as to protrude longitudinally outward from the outer end surface 402B of the trailing-side edge cutting steel plate 40B. The inner end surface 306B of the trailing-side main girder steel plate 30E is aligned with the inner end surface 406B of the trailing-side edge cutting steel plate 40B.

[0167] The force distribution steel material 97 is provided with one end side protruding outward a predetermined distance from the first side surface 401B of the trailing-side edge cutting steel plate 40B, and the other end side set back inward a predetermined distance from the second side surface 405B of the trailing-side edge cutting steel plate 40B. The protruding dimension of the force distribution steel material 97 from the first side surface 401B and the setback dimension from the second side surface 405B are designed to be equal.

[0168] In the outer end region of each trailing side main girder steel plate 30E, a trailing side perforated steel plate dowel 32E is rigidly joined by welding or the like to the first main surface 301B and the second main surface 302B. As shown in FIG. 68, each trailing side perforated steel plate dowel 32E protrudes from the first main surface 301B and the second main surface 302B of the trailing side main girder steel plate 30E toward the width direction of the trailing first steel shell unit 94C (trailing side edge cutting steel plate 40B) and is held in a position approximately parallel to the trailing side edge cutting steel plate 40B. A plurality of dowel holes 320 are drilled in each trailing side perforated steel plate dowel 32E. In the example shown in FIG. 68, four dowel holes 320 are arranged in the trailing side perforated steel plate dowel 32E along the long side direction. However, in the trailing-side perforated steel plate dowel 32E, there is no particular limitation on the number, shape, size, and arrangement pattern of the dowel holes 320. Also, the trailing-side perforated steel plate dowel 32E is provided at a position (height) near the center in the up-down direction (height direction) of the trailing-side main girder steel plate 30E.

[0169] In addition, an end plate (support steel plate) 34 similar to that of the leading inner circumference side steel shell element 91C is joined to the outer end surface 305B of each trailing side main girder steel plate 30E. In addition, in the trailing side main girder steel plate 30E, the general steel material portion 307 sandwiched between the outer end region and the inner end region is provided with anti-slip steel materials 308 at intervals. The arrangement intervals of the anti-slip steel materials 308 along the longitudinal direction of the general steel material portion 307 may be constant or may not be constant. The anti-slip steel materials 308 are provided in the vertical direction (from the lower end to the upper end) of the general steel material portion 307 in the trailing side main girder steel plate 30E. In addition, in the example shown in FIG. 68, the anti-slip steel materials 308 are provided on both the first main surface 301B and the second main surface 302B of the general steel material portion 307, but they may be provided on only one surface.

[0170] Next, referring to Fig. 69, the trailing second steel shell unit 94D of the trailing inner circumference side steel shell element 93C will be described. The trailing second steel shell unit 94 is a steel shell unit that has the same basic structure as the trailing first steel shell unit 94C described in Fig. 68. Specifically, the trailing second steel shell unit 94D has a configuration in which the structures of the inner end region and the outer end region in the long side direction of the trailing first steel shell unit 94C are interchanged. Individual members such as the trailing side edge cutting steel plate 40B, the trailing side main girder steel plate 30E, and the trailing side perforated steel plate dowel 32E included in the trailing second steel shell unit 94D are the same as those of the trailing first steel shell unit 94C, and detailed description thereof will be omitted here.

[0171] Next, the leading outer-periphery side steel-shell element 91D and the trailing outer-periphery side steel-shell element 93D will be described. Fig. 70 is a diagram for explaining the leading outer-periphery side steel-shell element 91D according to embodiment 2. (a) is a front view of the leading outer-periphery side steel-shell element 91D. (b) is a plan view of the leading outer-periphery side steel-shell element 91D viewed from the R direction in (a). (c) is a side view of the leading inner-periphery side steel-shell element 91C viewed from the S direction in (a). Note that (a) illustrates the leading outer-periphery side steel-shell element 91D as viewed from the starting base side.

[0172] The basic structure of the leading outer periphery side steel shell element 91D is the same as that of the leading inner periphery side steel shell element 91C described above, and is configured to include a leading side edge cutting steel plate 40A and a leading side main girder steel plate 30D erected from the leading side edge cutting steel plate 40A. In the leading outer periphery side steel shell element 91D, the leading side edge cutting steel plate 40A and the leading side main girder steel plate 30D are also curved in an arc shape in front view so as to follow the circumferential direction of the outer shell shield 4 to be constructed. Furthermore, when the leading outer peripheral side steel shell element 91D is installed in the outer shell structure construction area A21 (see FIG. 21) of the leading shield 5, the first side surface 401A of the leading side edge cutting steel plate 40A faces the tip portion 5A (see FIG. 9) of the leading shield 5, the second side surface 405A of the leading side edge cutting steel plate 40A faces the starting base 7, and the edge cutting surface 404A of the leading side edge cutting steel plate 40A faces the upper side of the leading shield 5 (the outer peripheral side of the outer shell shield 4). Furthermore, in the leading outer peripheral side steel shell element 91D, the edge cutting surface 404A of the leading side edge cutting steel plate 40A is arranged to face the upper side of the leading shield 5 (the outer peripheral side of the outer shell shield 4).

[0173] Next, the trailing first steel-shell unit 94E and the trailing second steel-shell unit 94F of the trailing outer periphery side steel-shell element 93D will be described with reference to Figures 71 and 72. Figure 71 is a diagram for explaining the trailing first steel-shell unit 94E of the trailing outer periphery side steel-shell element 93D according to embodiment 2. (a) is a front view of the trailing first steel-shell unit 94E. (b) is a plan view of the trailing first steel-shell unit 94E as viewed from the T direction in (a). Figure 72 is a diagram for explaining the trailing second steel-shell unit 94F of the trailing outer periphery side steel-shell element 93D according to embodiment 2. (a) is a front view of the trailing second steel-shell unit 94F. (b) is a plan view of the trailing second steel-shell unit 94F as viewed from the U direction in (a).

[0174] The trailing first steel shell unit 94E and the trailing second steel shell unit 94F of the trailing outer peripheral steel shell element 93D have substantially the same structure as the trailing first steel shell unit 94C and the trailing second steel shell unit 94D of the trailing inner peripheral steel shell element 93C, respectively, except that when installed inside the segment of the trailing shield 6, the edge cutting surface 404B of the trailing side edge cutting steel plate 40B is positioned facing the upper side of the trailing shield 6 (the outer peripheral side of the outer shell shield 4).

[0175] Next, the construction procedure in the underground widening section 1 according to the second embodiment will be described, focusing on the differences from the first embodiment. In this embodiment, as in the first embodiment, the leading outer shell structure 9A is constructed in the leading shield 5 prior to the construction of the trailing shield 6. Specifically, as in the procedure described in FIG. 19, the leading inner periphery side steel shell element 91C and the leading outer periphery side steel shell element 91D are positioned and fixed at predetermined positions in the outer shell structure construction area A21 of the leading shield 5, and the end areas AE1 and AE2 of the leading inner periphery side steel shell element 91C and the leading outer periphery side steel shell element 91D are box-cut by the box-cutting formwork 15, and the structure concrete 92 is poured in the outer shell structure construction area A21. The construction of the non-structural elements 57 and 58 in the leading shield 5 is the same as in the first embodiment.

[0176] In this embodiment as well, the leading outer shell body portion 9A can be constructed over the entire section of the leading shield 5 by successively extending the leading outer shell body portion 9A from the tip portion 5A side of the leading shield 5 toward the starting base 7 side.

[0177] FIG. 73 shows a leading inner circumferential steel shell element 91C according to the second embodiment in the axial direction of the leading shield 5. 73 is a diagram for explaining a state in which the leading inner periphery side steel shell elements 91C are connected to each other in the axial direction of the leading shield 5 by welding, bolting, or the like. In addition, the force distribution steel materials 97 of the leading inner periphery side steel shell elements 91C connected to each other in the axial direction of the leading shield 5 are arranged continuously in a straight line, and the force distribution steel materials 97 continuous in a straight line are welded to each other. Note that in FIG. 73, the leading inner periphery side steel shell element 91C is used as an example for explanation, but the same applies to the leading outer periphery side steel shell element 91D.

[0178] In addition, as shown in Figures 66 and 70(c), a backing plate 98 is provided along the edge of the edge cutting surface 404A of the leading side edge cutting steel plate 40A on the second side surface 405A side arranged on the starting base side. When connecting the leading inner periphery side steel shell elements 91C (leading outer periphery side steel shell elements 91D) to each other in the axial direction of the leading shield 5, the edge of the leading side edge cutting steel plate 40A on the first side surface 401A side of the leading inner periphery side steel shell element 91C (leading outer periphery side steel shell element 91D) of the other leading inner periphery side steel shell element 91C (leading outer periphery side steel shell element 91D) can be placed on the backing plate 98 of the leading inner periphery side steel shell element 91C (leading outer periphery side steel shell element 91D). This makes it possible to easily connect the leading inner periphery side steel shell elements 91C (leading outer periphery side steel shell elements 91D) to each other.

[0179] Next, the construction procedure of the trailing outer shell body part 9B in the trailing shield 6 will be described. Specifically, after constructing each trailing shield 6 in the same procedure as in embodiment 1, a part of the steel segment 61 in the trailing shield 6 is cut open as described in FIG. 27 to connect the trailing shield 6 and the leading shield 5. Then, the trailing inner periphery side steel-shell element 93C and the trailing outer periphery side steel-shell element 93D are positioned and fixed in the outer shell body construction area B21 of the trailing shield 6. Specifically, the trailing inner periphery side steel-shell element 93A and the trailing outer periphery side steel-shell element 93B in FIG. 51 are replaced with the trailing inner periphery side steel-shell element 93C and the trailing outer periphery side steel-shell element 93D, respectively, and installed. At that time, the trailing inner steel shell element 93C joins the inner end regions of the trailing first steel shell unit 94C and the trailing second steel shell unit 94D with the trailing perforated steel plate dowels 32E in each trailing main girder steel plate 30E of the trailing first steel shell unit 94C and the trailing second steel shell unit 94D inserted and positioned relative to the dowel joint regions of the leading inner steel shell element 91C in the leading shields 5 located on both sides of the trailing shield 6.

[0180] The joining of the inner end regions of the trailing first steel shell unit 94C and the trailing second steel shell unit 94D is performed by joining the inner end region of the trailing main girder steel plate 30E on the trailing first steel shell unit 94C side and the inner end region of the trailing main girder steel plate 30E on the trailing second steel shell unit 94D side via a splice plate 100, as shown in FIG. 74 (a) is a view of the joint between the inner end regions of the trailing main girder steel plate 30E viewed from the top surface side, and (b) is a view viewed from the side. The splice plate 100 has joining bolt holes 100A for inserting bolts at appropriate positions, and is joined by using bolts (not shown) in a state where it is spliced ​​across the inner end regions of a pair of trailing main girder steel plates 30E.

[0181] Similarly, for the trailing outer periphery steel shell element 93D, the trailing perforated steel plate dowels 32E in the trailing main girder steel plates 30E of the trailing first steel shell unit 94E and the trailing second steel shell unit 94F are inserted and positioned in the dowel joint regions of the leading outer periphery steel shell element 91D in the leading shield 5 located on both sides of the trailing shield 6, and the inner end regions of the trailing first steel shell unit 94E and the trailing second steel shell unit 94F are joined together. A splice plate 100 shown in FIG. 74 can be used to join the inner end regions of the trailing first steel shell unit 94E and the trailing second steel shell unit 94F together.

[0182] As described above, the trailing inner circumferential steel shell element 93C (the trailing outer circumferential steel shell element 93D) is connected in the axial direction of the trailing shield 6. The trailing inner circumferential side steel shell elements 93C (trailing outer circumferential side steel shell elements 93D) are connected to each other by welding or bolting. At that time, the force distribution steel materials 97 of the leading inner circumferential side steel shell elements 91C (leading outer circumferential side steel shell elements 91D) arranged in series in the axial direction of the trailing shield 6 are arranged continuously in a straight line, and the force distribution steel materials 97 continuing in a straight line are welded to each other.

[0183] FIG. 75 is a diagram showing a state in which the trailing perforated steel plate dowels 32E of the trailing main girder steel plate 30E in the trailing first steel shell unit 94C and the trailing second steel shell unit 94D are inserted into the dowel joint region of the leading inner circumference side steel shell element 91C of the embodiment 2 in which the end region is boxed out, and positioning is completed. The "longitudinal joint" in the figure indicates the joint location where the leading inner circumference side steel shell elements 91C and the trailing inner circumference side steel shell elements 93C connected in the axial direction of the outer shell shield 4 are connected to each other. As described above, the leading inner circumference side steel shell elements 91C and the trailing inner circumference side steel shell elements 93C connected in the axial direction of the outer shell shield 4 can be joined by an appropriate joining method such as welding or bolt joining. In addition, the "transverse joint 1" in the figure indicates the joint location of the leading inner circumference side steel shell element 91C and the trailing inner circumference side steel shell element 93C connected in the circumferential direction of the outer shell shield 4. Also, "transverse joint 2" in the figure indicates the joint position of the trailing first steel shell unit 94C and the trailing second steel shell unit 94D in the trailing inner circumference side steel shell element 93C. As described above, the trailing first steel shell unit 94C and the trailing second steel shell unit 94D are bolted together via a splice plate 100. Note that, although FIG. 75 shows an example of the positioning relationship of the trailing inner circumference side steel shell element 93C relative to the leading inner circumference side steel shell element 91C, the positioning relationship of the trailing outer circumference side steel shell element 93D relative to the leading outer circumference side steel shell element 91D is also the same as the embodiment shown in FIG. 75.

[0184] FIG. 76 is a diagram for explaining the arrangement relationship between the leading side perforated steel plate dowel 32D of the leading side main girder steel plate 30D in the leading inner periphery side steel shell element 91C (leading outer periphery side steel shell element 91D) according to the second embodiment and the trailing side perforated steel plate dowel 32E of the trailing side main girder steel plate 30E in the trailing inner periphery side steel shell element 93C (trailing outer periphery side steel shell element 93D). FIG. 77 is a V-V cross-sectional view of FIG. 76. Note that in FIG. 76, the illustration of the distribution steel material 97, the restraining steel plate 96, etc. is omitted. As shown in FIG. 76, the leading side perforated steel plate dowel 32D provided in the end region of the leading side main girder steel plate 30D and the trailing side perforated steel plate dowel 32E provided in the end region of the trailing side main girder steel plate 30E are arranged opposite to each other with a gap in the lateral direction. In this way, from a state in which the leading side perforated steel plate dowel 32D on the leading inner circumference side steel shell element 91C (leading outer circumference side steel shell element 91D) side and the trailing side perforated steel plate dowel 32E on the trailing inner circumference side steel shell element 93C (trailing outer circumference side steel shell element 93D) side are arranged opposite each other with a horizontal gap between them (hereinafter referred to as the ``dowel positioning state''), the structural concrete 95 and non-structural elements 67, 68 are constructed in the trailing shield 6 in an appropriate order, as in the above-mentioned embodiment 1.

[0185] When concrete is poured in the outer shell construction region B21 of the trailing shield 6, concrete is poured in the region sandwiched between the trailing edge cutting steel plate 40B of the trailing inner periphery side steel shell element 93C and the trailing edge cutting steel plate 40B of the trailing outer periphery side steel shell element 93D, so that the trailing side main girder steel plate 30E of each of the trailing inner periphery side steel shell element 93C and the trailing outer periphery side steel shell element 93D is covered with concrete to form an integral structure with the concrete structure 95. Of course, when constructing the concrete structure 95, concrete is also filled in the box-out portions 16 of each leading shield 5 connected to both sides of the trailing shield 6 and in the space formed by removing the cutting element 56 in the cutting region A1 of the leading shield 5, as in the first embodiment.

[0186] In the above-mentioned dowel joint region, the perforated steel dowels 32D and 32E arranged opposite each other with a gap in the horizontal direction as shown in Fig. 76 are embedded in the concrete structure 95. As a result, the leading perforated steel dowels 32D and the trailing perforated steel dowels 32E arranged opposite each other are embedded in the concrete structure 95. The perforated steel plate dowels 32E are joined together via the concrete structure 95.

[0187] Fig. 78 is a diagram showing the dowel joint region and its surroundings after concrete is poured in the second embodiment. In Fig. 78, the illustration of the restraining steel plate 96 is omitted. As described above, the leading side perforated steel plate dowel 32D and the trailing side perforated steel plate dowel 32E are arranged opposite to each other with a gap in the lateral direction, and these perforated steel plate dowels 32D, 32E are integrated in a state of being embedded in the concrete structure 95. This enables stress transmission between the leading side perforated steel plate dowel 32D and the trailing side perforated steel plate dowel 32E via the concrete structure 95, thereby enabling stress transmission between the leading side main girder steel plate 30D of the leading inner circumference side steel shell element 91C (leading outer circumference side steel shell element 91D) and the trailing side main girder steel plate 30E of the trailing inner circumference side steel shell element 93C (trailing outer circumference side steel shell element 93D).

[0188] Furthermore, according to this embodiment, the restraining steel plate 96 and the restraining steel plate portion 408 are provided so as to cover the upper and lower parts of the leading side perforated steel plate dowel 32D and the trailing side perforated steel plate dowel 32E in the dowel joint region. In addition to restraining the structural concrete 95 cast in the dowel joint region from the side by the end regions of the leading side main girder steel plate 30D and the trailing side main girder steel plate 30E arranged at an interval as a so-called open lap joint, the structural concrete 95 cast in the dowel joint region can also be restrained from the top and bottom by the restraining steel plate 96 and the restraining steel plate portion 408. This makes it possible to more suitably suppress splitting failure of the concrete cast in the dowel joint region. That is, when an axial tensile force acts on the leading side main girder steel plate 30D and the trailing side main girder steel plate 30E, the axial tensile force is transmitted to the concrete body 95 via the leading side perforated steel plate dowel 32D and the trailing side perforated steel plate dowel 32E, and as a result, a shear force is generated in the concrete body 95. In contrast, according to this joint structure, the concrete body 95 can be restrained from above and below not only by the leading side main girder steel plate 30D and the trailing side main girder steel plate 30E, but also by the restraining steel plate 96 and the restraining steel plate portion 408. This can improve the shear strength of the concrete body 95 cast in the dowel joint region, and can further improve the joint strength.

[0189] Furthermore, in this embodiment, the end plates 34 are provided on the end faces of the leading side main girder steel plate 30D and the trailing side main girder steel plate 30E. Therefore, the concrete structure 95 cast in the dowel joint region can be restrained from the end direction by the end plates 34. As shown in FIG. 78, the end plates 34 of the leading side main girder steel plate 30D and the trailing side main girder steel plate 30E are arranged along the boundary between the dowel joint region and the general region located outside of it. According to this, when stress is applied to the leading side main girder steel plate 30D and the trailing side main girder steel plate 30E, the concrete structure 95 cast in the dowel joint region is restrained by the support pressure Fb of the end plates 34, so that the cracking of the concrete structure 95 can be further suppressed and the joint strength can be further improved.

[0190] Furthermore, in this embodiment, the general steel material parts 307 of the leading-side main girder steel plate 30D and the trailing-side main girder steel plate 30E are provided with anti-slip steel materials 308. This makes it possible to increase the adhesive strength between the general steel material parts 307 of the leading-side main girder steel plate 30D and the trailing-side main girder steel plate 30E and the concrete, thereby further integrating them.

[0191] In this manner, the outer shell ring body 9 can be constructed by the leading outer shell body portion 9A and the trailing outer shell body portion 9B that are alternately arranged along the outer shell shield 4. The construction procedure for the underground widening section 1 thereafter is the same as in embodiment 1. As shown in FIG. 63, shear reinforcement steel 99A, 99B are arranged around the entire circumference of the outer shell shield 4 (outer shell ring body 9). Here, the shear reinforcement steel 99A is a shear reinforcement steel (hereinafter referred to as "shear reinforcement steel for joint section") that is arranged at a position corresponding to the dowel joint area, and shear reinforcement steel 99B (hereinafter referred to as "shear reinforcement steel for general section") is arranged in the other general sections. Fig. 79 is a diagram showing shear reinforcement steel members 99A and 99B according to the second embodiment. (a) shows the shear reinforcement steel member 99A for a joint portion, and (b) shows the shear reinforcement steel member 99B for a general portion. The shear reinforcement steel member 99A for a joint portion and the shear reinforcement steel member 99B for a general portion are each configured to include a main body portion 990 and hook portions 991A and 991B formed on both ends of the main body portion 990. As shown in Fig. 79, the shear reinforcement steel member 99A for a joint portion has a shorter main body portion 990 than the shear reinforcement steel member 99B for a general portion.

[0192] Here, the hook portions 991A, 991B of the joint shear reinforcement steel 99A are inserted into the retaining holes 963A (see FIG. 66) of the shear reinforcement steel retaining portion 963 provided on the leading inner periphery side steel shell element 91C side and the retaining holes 963A (see FIG. 70) of the shear reinforcement steel retaining portion 963 provided on the leading outer periphery side steel shell element 91D side, and welded as necessary. This allows the joint shear reinforcement steel 99A to be installed so as to span between the leading inner periphery side steel shell element 91C and the leading outer periphery side steel shell element 91D, as shown in FIG. In addition, the general shear reinforcement steel 99B arranged in the leading outer shell body section 9A has hook sections 991A, 991B inserted into notches 309 (gaps between the bottom surface 304A of the leading side main girder steel plate 30D and the main girder supporting surface 403A of the leading side edge cutting steel plate 40A) of the leading inner circumference side steel shell element 91C and the leading outer circumference side steel shell element 91D, respectively, and welded as necessary. In addition, the general shear reinforcement steel material 99B arranged in the trailing outer shell body part 9B has its hook part 991A inserted into a gap formed between the bottom surface 304B of the trailing main girder steel plate 30E in the trailing inner periphery side steel shell element 93C and the main girder holding surface 403B of the trailing edge cutting steel plate 40B, and the hook part 991B is inserted into a gap formed between the bottom surface 304B of the trailing main girder steel plate 30E in the trailing outer periphery side steel shell element 93D and the main girder holding surface 403B of the trailing edge cutting steel plate 40B, and is welded as necessary. In this manner, the shear reinforcement steel materials 99A, 99B can be installed at a predetermined pitch over the entire circumference of the outer shell ring body 9.

[0193] Although the preferred embodiments of the present invention have been described above, the present invention can be implemented by combining the embodiments and modifications as much as possible. [Explanation of symbols]

[0194] 1. Underground widening section 2. Mains shield 3. Lamp shield 4. Outer shell shield 5. Preceding Shield 6. Trailing shield 7. Launch base 9. Outer shell ring body 9A: Leading outer shell body 9B: Rear shell body 10... Outer shell lining 30A Leading side main girder steel plate 30B... Trailing side 1st main girder steel plate 30C...Second main girder steel plate on trailing side 32A... Leading side perforated steel plate dowel 32B... Trailing side 1st perforated steel plate dowel 32C···Second perforated steel plate dowel on rear side 91A: Leading inner shell element 91B: Leading outer periphery steel shell element 93A Trailing inner shell element 93B Trailing outer periphery steel shell element 92,95...Concrete structure

Claims

1. A construction method for an outer shell lining in a large cross-section tunnel, an outer shell construction process for forming a ring-shaped outer shell shield tunnel by connecting segments of a plurality of small cross-section shield tunnels arranged in parallel underground in a rosary-like manner; An outer shell ring skeleton construction process for forming an outer shell ring skeleton including an annular steel main girder ring extending along the circumferential direction of the outer shell shield tunnel inside the outer shell shield tunnel and a skeleton concrete covering the steel main girder ring; having The steel main girder ring includes a plurality of main girder steel plates that are jointed to each other via perforated steel plate dowels rigidly connected to both ends in the longitudinal direction, In the outer shell ring skeleton construction process, perforated steel plate dowels arranged at the ends of the main girder steel plates to be joined to each other are arranged facing each other with a gap between them, and concrete is poured into the outer shell shield tunnel so that the perforated steel plate dowels are embedded in the concrete, and the main girder steel plates are joined to each other via the concrete. Method for constructing the outer shell lining.

2. In the outer shell ring structure construction process, a leading shield machine is launched from a launch base constructed underground, and a plurality of leading shield tunnels in which cuttable segments are arranged are constructed at intervals from each other, and then a trailing shield machine is launched from the launch base, and a plurality of trailing shield tunnels are constructed while cutting a portion of the leading shield tunnel between adjacent leading shield tunnels, thereby connecting the alternating leading shield tunnels and the trailing shield tunnels in a rosary shape, and the outer shell shield tunnel is formed by cutting open a segment of the trailing shield tunnel located at the boundary between the leading shield tunnel and the leading shield tunnel. A method for constructing the shell covering structure according to claim 1.

3. The steel main girder ring includes a leading side main girder steel plate laid horizontally in the leading shield tunnel so as to extend along the circumferential direction of the outer shell shield tunnel, and a trailing side main girder steel plate laid horizontally in the trailing shield tunnel so as to extend along the circumferential direction of the outer shell shield tunnel, In the outer shell ring body construction process, a leading side perforated steel plate dowel, which is a perforated steel plate dowel arranged at the end of the leading side main girder steel plate, and a perforated steel plate dowel arranged at the end of the trailing side main girder steel plate The trailing perforated steel plate dowel is joined together via concrete. A method for constructing the outer shell covering structure according to claim 2.

4. In the outer shell ring structure construction process, before constructing the trailing shield tunnel, a leading outer shell structure portion that will become a part of the outer shell ring structure is constructed in advance in a predetermined outer shell structure construction area within the leading shield tunnel that does not include a cutting area to be cut by the trailing shield machine, When constructing the preceding outer shell skeleton portion, a box punching portion is formed in an end region including the preceding side perforated steel plate dowel in the preceding side main girder steel plate, for punching concrete into a box; After the trailing shield tunnel is constructed, the trailing perforated steel plate dowel of the trailing main girder steel plate is inserted into the box-opening portion, and concrete is filled in the trailing shield tunnel and in the box-opening portion to integrally join the ends of the leading main girder steel plate and the trailing main girder steel plate, and a trailing outer shell body portion that becomes part of the ring body is constructed in the trailing shield tunnel. A method for constructing the outer shell covering structure according to claim 3.

5. In the outer shell ring body construction process, concrete is poured into the outer shell shield tunnel in a state where a rod-shaped or plate-shaped reinforcing iron material is inserted so as to straddle the dowel hole of one of the perforated steel plate dowels arranged opposite to each other and the dowel hole of the other perforated steel plate dowel. A method for constructing an outer shell covering structure according to any one of claims 1 to 4.

6. In the outer shell ring body construction process, the leading side perforated steel plate dowel and the trailing side perforated steel plate dowel are arranged opposite each other with a gap in the vertical direction. A method for constructing an outer shell covering structure according to claim 3 or 4.

7. The method for constructing an outer shell covering structure according to claim 6, wherein in the outer shell ring body construction process, the end regions of the leading side main girder steel plate and the trailing side main girder steel plate are joined together in a facing state.

8. In the outer shell ring body construction process, the leading side main girder steel plate and the trailing side main girder steel plate are arranged opposite each other with a gap in the lateral direction, and the leading side perforated steel plate dowel and the trailing side perforated steel plate dowel are arranged opposite each other with a gap in the lateral direction. A method for constructing an outer shell covering structure according to claim 3 or 4.

9. The method for constructing an outer hull covering structure according to claim 8, wherein end plates are rigidly connected to end faces of the leading side main girder steel plate and the trailing side main girder steel plate.

10. A method for constructing an outer shell covering structure as described in claim 8 or 9, wherein a restraining steel plate for restraining concrete is provided at the joint portion of the leading side main girder steel plate and the trailing side main girder steel plate so as to cover the upper and lower parts of the leading side perforated steel plate dowel and the trailing side perforated steel plate dowel.

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