Large-section tunnels and their construction methods

Abstract

This invention relates to a large-diameter tunnel formed by the coexistence of multiple small-diameter tunnels, and to a construction method thereof, and provides a large-diameter tunnel and a construction method thereof that exhibits excellent watertightness between adjacent small-diameter tunnels. [Solution] A large cross-section tunnel 100 is formed by arranging multiple small cross-section tunnels 20 side by side along a rectangular frame-shaped line L perpendicular to the axis of the tunnel. The tunnel boxes 10 of adjacent small cross-section tunnels 20 are equipped with a strip-shaped axial waterproofing material 31 that extends axially at the inner end faces 10b of the outer shells 10a on both sides facing the ground. Waterproofing steel plates 33 are attached across the boundary between the two small cross-section tunnels 20, and in both tunnel boxes 10, the axial waterproofing material 31 is sandwiched between the inner end faces 10b of the outer shells 10a and the waterproofing steel plates 33.

Description

Technical Field

[0001] The present invention relates to a large-section tunnel and a construction method therefor.

Background Art

[0002] For example, when constructing an underpass grade separation to alleviate traffic congestion in urban areas, the method that requires setting up a construction yard on the ground and constructing the frame via an open-cut method needs a large construction yard and leads to a prolonged construction period, which may cause problems such as new traffic congestion and impacts on the surrounding environment. Therefore, when constructing a tunnel having a cross-section sized to correspond to a large-section rectangular underground structure (underpass) for example, a construction method is sometimes used in which the large-section tunnel is divided into a plurality of small-section tunnels, each small-section tunnel is repeatedly excavated and formed with a small excavator, and then a large-section rectangular underground structure, for example, is constructed inside these tunnels. This construction method is called the harmonica method (registered trademark) because the shape of the tunnel portal formed by stacking small-section tunnels resembles the mouthpiece of a harmonica. In the above-mentioned harmonica method, a plurality of rectangular frame-shaped tunnel boxes are joined in the axial direction of the tunnel by the jacking method or the shield method to construct small-section tunnels, and a large-section tunnel is constructed by sequentially constructing a plurality of small-section tunnels arranged vertically and / or horizontally. Here, the number of small-section tunnels, that is, the number of divisions for the cross-section of the large-section tunnel, is determined by the dimensions of the underpass to be constructed, site conditions, transportation conditions for the excavator and steel shells, and other factors.

[0003] Here, Patent Document 1 proposes a large-section tunnel constructed by the above-mentioned harmonica method and a construction method therefor. This large-section tunnel is a large-section tunnel having a top slab, a bottom slab, and left and right side walls, which is formed by connecting a plurality of small-section tunnels arranged side by side via the jacking method. This large-section tunnel comprises a steel shell that is arranged in a series along the tunnel axis to form small-section tunnels, tensile reinforcement bars at joints arranged across the boundary between adjacent small-section tunnels, bearing plates fixed within the steel shell so as to face each other at both ends of the tensile reinforcement bars at joints, and concrete filled within the small-section tunnels. The steel shell comprises frame-shaped main girders arranged in parallel at predetermined intervals along the tunnel axis, longitudinal ribs arranged in parallel along the tunnel axis between the main girders, and main girder reinforcing members arranged across two mutually orthogonal or opposing sides of the main girders. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-58299 [Overview of the project] [Problems that the invention aims to solve]

[0005] According to the large-diameter tunnel and its construction method described in Patent Document 1, it becomes possible to construct a large-diameter tunnel simply and inexpensively. Incidentally, when constructing the large-section tunnels mentioned above, the adjacent tunnel boxes are connected by removing the opposing main girders, which are rectangular frame-shaped main girders that make up the tunnel boxes of adjacent small-section tunnels. This allows the large-section tunnels to be constructed. In this way, since the opposing main girders on both sides of adjacent tunnel boxes are removed, there is a concern that groundwater may infiltrate (leak) through the joints between the tunnel boxes, i.e., the joints of the adjacent small-section tunnels. Therefore, waterproofing measures at these joints become an issue.

[0006] The present invention relates to a large-diameter tunnel constructed by arranging multiple small-diameter tunnels side by side, and a method for constructing the same, with the aim of providing a large-diameter tunnel and a method for constructing the same that exhibits excellent watertightness between adjacent small-diameter tunnels. [Means for solving the problem]

[0007] To achieve the above objective, one embodiment of the large-section tunnel according to the present invention is: A large-section tunnel is formed by connecting multiple rectangular frame-shaped tunnel boxes in the axial direction of the tunnel via ring joints using a tunneling method or a shield tunneling method, thereby forming small-section tunnels, and then arranging multiple such small-section tunnels side by side along a rectangular frame-shaped line perpendicular to the tunnel axis. The tunnel box comprises a plurality of rectangular frame-shaped main girders arranged at intervals in the axial direction, skin plates attached to the periphery of the plurality of main girders, and longitudinal ribs extending in the axial direction and connecting the plurality of main girders. Both of the adjacent small-section tunnels are equipped with a strip-shaped axial watertight material extending in the axial direction at the inner end face of the outer shell on the ground side of both tunnels. A watertight steel plate is installed across the boundary between the adjacent small-section tunnels. In both of the aforementioned tunnel boxes, the axial water-sealing material is characterized in that it is sandwiched between the inner end face of the outer shell and the water-sealing steel plate.

[0008] According to this embodiment, both tunnel boxes of adjacent small-section tunnels are equipped with a strip-shaped axial watertight material extending axially at the inner end faces of the outer shells on the ground side of both tunnel boxes, a watertight steel plate is attached across the boundary between the adjacent small-section tunnels, and the axial watertight material is sandwiched between the inner end faces of the outer shells and the watertight steel plate in both tunnel boxes, thereby enabling the formation of a large-section tunnel with excellent watertightness between adjacent small-section tunnels.

[0009] Multiple watertight steel plates are sequentially installed, extending in the axial direction of the tunnel, spanning multiple tunnel boxes of adjacent small-section tunnels. The watertight steel plates can be connected to each other, for example, by overlapping some of them and welding or bolting the overlapping sections.

[0010] Examples of axial water-sealing materials include axial, standard-shaped gaskets and fillable sealing materials.

[0011] Furthermore, in another embodiment of the large-section tunnel according to the present invention, The aforementioned small cross-section tunnel is equipped with a ring-to-ring water-sealing material in the ring joint, The ring-interlocking water-sealing material and the axial-axis water-sealing material are continuous.

[0012] According to this embodiment, a small-section tunnel is equipped with a ring-to-ring waterproofing material at the ring joint, and the ring-to-ring waterproofing material and the axial waterproofing material are continuous, thereby enabling the formation of a large-section tunnel that is excellent in both watertightness between adjacent small-section tunnels and watertightness between tunnel boxes connected in the axial direction of the tunnels forming the small-section tunnels.

[0013] Here, the inter-ring waterproofing material can be similar to the axial waterproofing material, and examples include axial, standard-shaped gaskets and fillable sealing materials.

[0014] Furthermore, in another embodiment of the large-section tunnel according to the present invention, The inner end face of the outer shell is characterized by being the inner end face of a plurality of main girders located on the ground side.

[0015] According to this embodiment, since the inner end face of the outer shell on which the axial water-sealing material is provided is the inner end face of a plurality of main girders located on the ground side, a water-sealing structure can be formed between small-section tunnels in the ground-side region of adjacent tunnel boxes.

[0016] Furthermore, other embodiments of the large-section tunnel according to the present invention are: A common watertight steel plate is attached to a plurality of tunnel boxes that are connected axially via the ring joint.

[0017] According to this embodiment, by attaching a common watertight steel plate across multiple tunnel bodies of adjacent small-section tunnels, the number of connection points between the watertight steel plates can be reduced, further improving watertightness and making the installation of the watertight steel plates easier.

[0018] Another aspect of the large-section tunnel according to the present invention is the water-stop steel plate is attached to a removed area where an opposing main girder opposing to an adjacent small-section tunnel among the rectangular frame-shaped main girders has been removed, and a replacement girder that serves as a substitute for the removed opposing main girder is replaced and installed in the vicinity of the removed area of the opposing main girder.

[0019] According to this aspect, the water-stop steel plate is attached to the removed area where the opposing main girder opposing to the adjacent small-section tunnel among the rectangular frame-shaped main girders has been removed, and the replacement girder is replaced and installed in the vicinity of the removed area, whereby a reduction in rigidity of the tunnel box caused by the removal of the opposing main girder can be suppressed.

[0020] One aspect of the construction method for a large-section tunnel according to the present invention is a construction method for a large-section tunnel formed as follows: a small-section tunnel is formed by joining a plurality of rectangular frame-shaped tunnel boxes in the axial direction of the tunnel via ring joints by a jacking method or a shield method, and a plurality of the small-section tunnels are arranged side by side along a rectangular frame-shaped line in the direction perpendicular to the axis of the tunnel, wherein the tunnel box comprises: a plurality of rectangular frame-shaped main girders arranged at intervals in the axial direction; a skin plate and a joint plate attached to the peripheral edges of the plurality of main girders; and longitudinal ribs extending in the axial direction and connecting the plurality of main girders, the tunnel boxes of both adjacent small-section tunnels each include a band-shaped axial water-stop material extending in the axial direction on an inner-space side end surface of an outer shell located on the natural ground side of both tunnel boxes, a water-stop steel plate is attached across the boundary between the adjacent small-section tunnels, in both of the tunnel boxes, the axial water-stop material is sandwiched between the inner-space side end surface of the outer shell and the water-stop steel plate.

[0021] According to this embodiment, both tunnel boxes of adjacent small-section tunnels are equipped with a strip-shaped axial watertight material extending axially at the inner end faces of the outer shells on the ground side of both tunnel boxes, a watertight steel plate is attached across the boundary between the adjacent small-section tunnels, and the axial watertight material is sandwiched between the inner end faces of the outer shells and the watertight steel plate in both tunnel boxes, thereby forming a large-section tunnel with excellent watertightness between adjacent small-section tunnels.

[0022] In either the tunneling method or the shield tunneling method, a closed-type tunneling machine may be positioned in front of the tunnel body in the direction of excavation. Alternatively, ground improvement work may be carried out in advance in the construction area, and the tunnel body may be installed underground using an open-type tunneling method, where the cutting edge is provided in front of the tunnel body in the direction of excavation and the front is open, provided that groundwater intrusion is prevented and the tunnel face is self-supporting.

[0023] Furthermore, other embodiments of the construction method for large-section tunnels according to the present invention include: The method is characterized by removing the opposing main girder of the rectangular frame-shaped main girder that faces the adjacent small-section tunnel to create a removal area, attaching the watertight steel plate to the removal area, and then installing the replacement beam of the removed opposing main girder.

[0024] According to this embodiment, by attaching a watertight steel plate to the removal area where the opposing main girder facing the adjacent small-section tunnel has been removed from the rectangular frame-shaped main girder, and by installing a replacement beam near the removal area, the reduction in rigidity of the tunnel box structure caused by the removal of the opposing main girder can be suppressed. [Effects of the Invention]

[0025] The present invention relates to a large-section tunnel and its construction method, which are constructed by arranging multiple small-section tunnels side by side, and it is possible to improve the watertightness between adjacent small-section tunnels. [Brief explanation of the drawing]

[0026] [Figure 1] This is a perspective view of an example of a large-section tunnel according to this embodiment. [Figure 2] This is an enlarged view of part II of Figure 1, showing two adjacent tunnel casings viewed from diagonally above. [Figure 3] This is an enlarged view of part III of Figure 1, showing two adjacent tunnel casings viewed from diagonally below. [Figure 4A] This is a longitudinal cross-section of the tunnel box, viewed from the front, showing the main girders extending along the rectangular frame-like lines inside the tunnel box. [Figure 4B] Figure 4A is a view along the BB arrow, showing a longitudinal cross-section of the tunnel box structure as seen along the rectangular frame-shaped line. [Figure 5] This is a perspective view showing two tunnel boxes of adjacent small-section tunnels, illustrating the state before the removal of the opposing main girders (removable main girders) on both sides. [Figure 6A] This is an enlarged view of section VI in Figure 5. [Figure 6B] This figure shows the state after the opposing main girders (detachable main girders) have been removed, the replacement beams have been installed, and the watertight steel plates have been installed, compared to the state shown in Figure 6A. [Figure 7] This is an enlarged view of section VII in Figure 1, showing an example of a reinforcement structure for the corner of a large-section tunnel. [Figure 8A] This is a plan view showing both the watertight lines between ring joints and the watertight lines between small-section tunnels in a large-section tunnel according to the embodiment. [Figure 8B] This is a view from arrow BB in Figure 8A. [Figure 9A] This is a plan view showing an example of the arrangement of guide materials applied to the construction method for a large-section tunnel according to the embodiment. [Figure 9B] This is a longitudinal cross-sectional view taken in a direction perpendicular to the tunneling direction, showing the positional relationship between each guide material and each small-section tunnel in the construction method for a large-section tunnel according to the embodiment. [Figure 10] This is a process diagram of an example of a construction method for a large-section tunnel according to the embodiment. [Figure 11A]This diagram shows an example of an excavation method for tunnel boxes located at the top and bottom (both horizontal) edges of a rectangular frame-shaped line. [Figure 11B] This figure shows an example of an excavation method for tunnel boxes located on the left and right sides (vertical sides) of a rectangular frame-shaped line. [Modes for carrying out the invention]

[0027] The large-section tunnel and its construction method according to the embodiment will be described below with reference to the attached drawings. In this specification and the drawings, substantially identical components may be denoted by the same reference numerals to avoid redundant explanations.

[0028] [Large-section tunnel according to an embodiment and its construction method] An example of a large-section tunnel and its construction method according to an embodiment will be described with reference to Figures 1 to 11. Here, Figure 1 is a perspective view of an example of a large-section tunnel according to the embodiment, Figure 2 is an enlarged view of part II of Figure 1, showing two adjacent tunnel bodies viewed from diagonally above, and Figure 3 is an enlarged view of part III of Figure 1, showing two adjacent tunnel bodies viewed from diagonally below. Furthermore, Figure 4A is a longitudinal cross-sectional view of the tunnel body, showing the main girder extending along a rectangular frame-shaped line from the front, and Figure 4B is a view of the tunnel body in the direction of arrow BB in Figure 4A, showing a longitudinal cross-sectional view of the tunnel body in the direction along the rectangular frame-shaped line. Figure 5 is a perspective view showing two tunnel boxes of adjacent small-section tunnels, showing the state before the removal of the opposing main girders (detachable main girders) on both sides. Figure 6A is an enlarged view of section VI of Figure 5. Figure 6B shows the state after the opposing main girders (detachable main girders) have been removed, the replacement beams have been installed, and the watertight steel plates have been installed, compared to the state shown in Figure 6A. Figure 7 is an enlarged view of section VII of Figure 1, showing an example of a reinforcement structure for the corner of a large-section tunnel. Figure 8A is a plan view showing both the watertight line between ring joints and the watertight line between small-section tunnels in a large-section tunnel according to the embodiment. Figure 8B is a view from arrow BB in Figure 8A. Figure 9A is a plan view showing an example of the arrangement of guide materials applied to the construction method of a large-section tunnel according to the embodiment. Figure 9B is a longitudinal cross-sectional view taken in a direction perpendicular to the tunneling direction, showing the positional relationship between each guide material and each small-section tunnel in the construction method of a large-section tunnel according to the embodiment. Furthermore, Figure 10 is a process diagram of an example of a construction method for a large-section tunnel according to the embodiment, and Figures 11A and 11B show an example of an excavation method for tunnel boxes located on the upper and lower sides (both horizontal sides) of a rectangular frame-shaped line, and an example of an excavation method for tunnel boxes located on the left and right sides (vertical sides), respectively.

[0029] The large-section tunnel 100 shown in Figure 1 is constructed by joining multiple rectangular frame-shaped tunnel boxes 10 in the axial direction of the tunnel via ring joints 10A to form small-section tunnels 20, and by arranging multiple small-section tunnels 20 side by side along a rectangular frame-shaped line L perpendicular to the axis of the tunnel.

[0030] Each tunnel box 10 in the illustrated example is constructed underground by being driven from a shaft T (see Figure 9A) in a predetermined direction. Here, the construction of the tunnel box 10 underground may be carried out by the shield tunneling method in addition to the tunnel jacking method.

[0031] Furthermore, the construction direction shown in the illustration is an open excavation method in which, when pushing up the tunnel box 10, a retaining wall D (see Figure 9A) is constructed, ground improvement work is carried out at least inside the retaining wall D, and the face is excavated from the inside of the tunnel box 10 while ensuring groundwater infiltration and the self-supporting nature of the tunnel face. Alternatively, regardless of whether ground improvement is performed, the tunnel box 10 may be installed underground by a construction method that cuts the ground using a closed-type tunnel boring machine.

[0032] The large-section tunnel 100 shown in Figure 1 is formed by tunnel boxes 10 with the same cross-sectional shape and dimensions perpendicular to the axis, with a short side length of t2, a long side length of t3, and a thickness (length in the axial direction) of t1.

[0033] Along the upper and lower edges (both horizontal edges) of the rectangular frame-shaped line L, three adjacent tunnel boxes 10 are arranged horizontally, while along the left and right sides (both vertical edges), two adjacent tunnel boxes 10 are arranged vertically.

[0034] A ring joint watertight line 50A is formed along the rectangular frame-shaped line that runs along the ring joint 10A of each small-section tunnel 20 that constitutes the large-section tunnel 100. In addition, an inter-small-section tunnel watertight line 50B is formed between adjacent small-section tunnels 20 along the axial direction. Details of the watertight structure that forms these watertight lines will be explained in detail below.

[0035] Figure 1 simulates the state in which each small-section tunnel 20 forming the large-section tunnel 100 underground has been constructed. However, in reality, as shown in Figure 10, concrete may be poured into the interior of the small-section tunnel 20 in areas requiring reinforcement in advance.

[0036] In the illustrated example, an existing structure exists above the construction area. From the viewpoint of suppressing ground subsidence during the construction of the large-section tunnel 100, three small-section tunnels 20 located on the upper edge of the rectangular frame-shaped line L are constructed first. After connecting the interiors of each small-section tunnel 20, concrete is poured into the interior of each small-section tunnel 20 to support the load of the existing structure above, and then the small-section tunnels 20 in the other areas are constructed sequentially.

[0037] As shown in Figures 2 and 3, the tunnel box 10 comprises a plurality of rectangular frame-shaped main girders 11 (three in the illustrated example) arranged at intervals in the axial direction, skin plates 13 attached to the periphery of the plurality of main girders 11, and a plurality of longitudinal ribs 15 extending in the axial direction and connecting the plurality of main girders 11.

[0038] The two tunnel boxes 10 shown in Figures 2 and 3 are tunnel boxes located on the upper or lower edge of the rectangular frame-shaped line L, and shear reinforcement members 16 made of multiple shaped steel materials (angle steel in the illustrated example) are attached between the main girders 11 located above and below each tunnel box 10. These shear reinforcement members 16 are welded to the main girders 11 and longitudinal ribs 15, etc., when the tunnel boxes 10 are manufactured in the factory.

[0039] Furthermore, with respect to the tunnel boxes 10 located on the sides of the rectangular frame-shaped line L, each tunnel box 10 will be rotated 90 degrees from the position shown in Figures 2 and 3, and therefore, shear reinforcement members 16 will be attached between the main girders 11 on the left and right.

[0040] The states shown in Figures 1 to 3 indicate that the detachable main girder 11A (opposing main girder, see Figures 5 and 6A), which was fitted into the recess 10b (internal end face) of the outer shell 10a of each tunnel box 10, has been removed, and a watertight steel plate 33 has been attached to the recess 10c (removal area of ​​the detachable main girder 11A) formed by the internal end face 10b of the adjacent tunnel box 10. The detachable main girder 11A is fitted into the upper and lower (or left and right) recesses 10b and is joined to the vertical ribs 15, etc., for example by bolt connections, and can be easily removed by releasing the bolt connections.

[0041] In other words, at the stage of constructing each small-section tunnel 20, as shown in Figure 5, each tunnel box 10 has three rectangular frame-shaped main girders 11, and the opposing main girders 11A (detachable main girders) on both sides are adjacent to the other tunnel box 10.

[0042] As shown in Figures 5 and 6A, in the state before the detachable main girder 11A is removed, a rectangular frame-shaped inter-ring waterproofing material 35 is provided on the side surface of the main girder 11 that forms the ring joint A. This inter-ring waterproofing material 35 is a waterproofing material formed by, for example, a axial, standard-shaped gasket.

[0043] As shown in Figures 6A and 6B, a strip-shaped axial waterproofing material 31 extending in the axial direction, as indicated by the dotted line, is attached to the recess 10b (the inner end face of the outer shell 10a) into which the end of the detachable main girder 11A is fitted in the tunnel box 10, and the axial waterproofing material 31 and the inter-ring waterproofing material 35 are continuous. This axial waterproofing material 31, like the inter-ring waterproofing material 35, is a waterproofing material formed, for example, by an axial, standard-shaped gasket.

[0044] From the state before the removal of the detachable main girders 11A shown in Figures 5 and 6A, the removal of the detachable main girders 11A of both adjacent tunnel boxes 10 results in the tunnel boxes 10 being connected to each other, as shown in Figures 1, 2, 3, and 6B.

[0045] As shown in detail in Figure 6B, in the recess 10c formed by the inner end face 10b of the outer shell 10a on the ground side of the adjacent tunnel box 10, a watertight steel plate 33 is attached from below, sandwiching the axial watertight material 31.

[0046] In other words, by installing the watertight steel plate 33, the axial watertight material 31, which is continuous with the inter-ring watertight material 35, comes into close contact with the watertight steel plate 33.

[0047] Here, the watertight steel plate 33 is installed so as to span not only the recesses 10c of an adjacent pair of tunnel boxes 10, but also the recesses 10c of multiple pairs of tunnel boxes 10 that are continuous in the axial direction (multiple recesses 10c). Furthermore, multiple watertight steel plates 33 that extend in the axial direction are joined to each other by welding or bolting at both ends.

[0048] In this way, by arranging a single watertight steel plate 33 so as to span multiple recesses 10c in the axial direction, the number of connection points of the watertight steel plates 33 arranged in the axial direction can be reduced, and the watertightness can be further improved.

[0049] In this way, the axial water-sealing material 31, the inter-ring water-sealing material 35, and the water-sealing steel plate 33 are connected to or in close contact with each other, so as shown in Figures 8A and 8B, a plurality of inter-small cross-section tunnel water-sealing lines 50B extending in the axial direction and a plurality of inter-ring joint water-sealing lines 50A extending perpendicular to the axis are formed, both of which form an excellent water-sealing structure.

[0050] Here, the flow of groundwater in the Y1 direction shown in Figures 8A and 8B is a flow that occurs on the outer perimeter of the large-diameter tunnel 100, as the intrusion of groundwater into the large-diameter tunnel 100 is prevented by the ring joint watertight line 50A. On the other hand, the flow of groundwater in the Y2 direction is a flow that occurs on the outer perimeter of the large-diameter tunnel 100, as the intrusion of groundwater into the large-diameter tunnel 100 is prevented by the small-diameter tunnel watertight line 50B.

[0051] Furthermore, as shown in Figure 6B, replacement beams 11B are installed near the area where the detachable main girder 11A (opposing main girder) is removed, to serve as a replacement for the removed detachable main girder 11A. For example, the ends of the replacement beams 11B, which are made of shaped steel (angle steel in the illustrated example), are installed to the vertical ribs 15 at corresponding positions above and below (or left and right) by welding or bolting.

[0052] In this way, when the detachable main girder 11A of an adjacent tunnel box 10 is removed and the two are connected, the reduction in rigidity of the tunnel box 10 caused by the removal of the detachable main girder 11A can be suppressed by installing a replacement beam 11B near the area where the detachable main girder 11A was removed.

[0053] As shown in Figures 4A and 4B, each tunnel box 10 has multiple through holes 15a in its longitudinal ribs 15. An axial force transmission member 17 inserted through the through holes 15a of each longitudinal rib 15 in one tunnel box 10 is then inserted through the through holes 15a of each longitudinal rib 15 in the other tunnel box 10, so that, as shown in Figures 2 and 3, the axial force transmission member 17 spans the interior of both tunnel boxes 10.

[0054] This axial force transmission member 17 is formed from steel rods, reinforcing bars, etc., and is a member that transmits axial force in the direction along the rectangular frame-shaped line L. Multiple axial force transmission members 17 are housed in the tunnel box 10 in advance for its propulsion. After the detachable main girder 11A of adjacent tunnel box 10 is removed, the axial force transmission member 17 is inserted through the through-hole 15a of the longitudinal rib 15 of one tunnel box 10, and then through the through-hole 15a of the longitudinal rib 15 of the other tunnel box 10.

[0055] Here, instead of inserting the axial force transmission member 17 through the through-holes provided in the longitudinal ribs 15, the axial force transmission member 17, which may be made of steel rods, reinforcing bars, flat steel, shaped steel, etc., may be welded to the longitudinal ribs 15 of both tunnel boxes 10. However, the configuration in which the axial force transmission member 17 is inserted through the through-holes is preferred because it eliminates or reduces welding work inside the tunnel box 10.

[0056] In Figures 2 and 3, corresponding axial force transmission members 17 are inserted through multiple through-holes 15a in the longitudinal ribs 15 connected to the upper and lower main girders 11, and the multiple axial force transmission members 17 are arranged so as to straddle both tunnel boxes 10.

[0057] Next, as shown in Figures 4A and 4B, the anchoring portions 18b of each of the multiple shear reinforcement members 18 (e.g., head bars), which have an axial member 18a such as a deformed reinforcing bar and anchoring portions 18b such as steel plates provided at both ends, are locked to a pair of axial force transmission members 17 located above and below.

[0058] In the end, concrete will be poured into the interior of the interconnected tunnel boxes 10, and the arrangement of main reinforcement bars along the rectangular frame lines and shear reinforcement bars perpendicular to them at the joints of the tunnel boxes 10 is carried out by multiple upper and lower axial force transmission members 17 extending in the direction along the rectangular frame-shaped lines and multiple shear reinforcement members 18 that are locked to a pair of upper and lower axial force transmission members 17.

[0059] Furthermore, at the joints between adjacent tunnel casings 10 located on the sides (vertical sides) of the rectangular frame-shaped line, the anchoring portions 18b of multiple shear reinforcement members 18, which extend in the horizontal direction, are locked to a pair of axial force transmission members 17 that extend in the vertical direction on the left and right sides.

[0060] In this way, by locking the anchoring portions 18b of the shear reinforcement member 18, which has anchoring portions 18b at both ends, to the pair of axial force transmission members 17, welding can be eliminated when installing the shear reinforcement member 18, thereby suppressing the prolonged work time and increased construction costs caused by welding work. Furthermore, a joint structure can be formed between tunnel boxes 10 that provides the same shear reinforcement effect as if the shear reinforcement members were welded together.

[0061] Furthermore, as shown in Figures 2 and 3, the upper (one) axial force transmission member 17 is positioned to straddle the recesses 10b of the corresponding tunnel boxes 10 that are exposed after the removal of the detachable main girder 11A, and the lower (other) axial force transmission member 17 is positioned in a corresponding location, with shear reinforcement members 18 being locked to both axial force transmission members 17.

[0062] This configuration allows the pair of axial force transmission members 17 to be positioned as far to the outside as possible of the tunnel body 10, thereby increasing the resistance of the tunnel body 10 to bending and other forces acting upon it.

[0063] For example, compared to the case where one of the axial force transmission members 17 (the upper one in Figures 2 and 3) is positioned inside (below) the recess 10b of the tunnel body 10, the position of the other axial force transmission member 17 can be about 10 to 10-something centimeters further outward, resulting in a significant improvement in the resistance to bending that is dominant on the outside of the tunnel body 10.

[0064] As shown in Figure 7, corner reinforcing steel members 95 extending diagonally are attached to the tunnel box 10 located at the corner 90 of the large-section tunnel 100. In addition, multiple shear reinforcing members 16 are pre-installed at the factory on the sides and above (not shown) of the corner 90, and when additional shear reinforcing members 16 are to be added on-site, they are joined to the upper and lower vertical ribs 15, etc., by welding or bolting on-site.

[0065] As explained above, according to the illustrated example of the large-section tunnel 100, the ring joint watertight line 50A and the small-section tunnel joint watertight line 50B result in a large-section tunnel with excellent watertight performance.

[0066] Furthermore, when joining the tunnel boxes 10 of adjacent small-section tunnels 20, a pair of axial force transmission members 17 are arranged to straddle both, and the anchoring portions 18b at both ends of the shear reinforcement member 18 are locked to these, thereby creating a large-section tunnel that guarantees high shear strength at the joint while eliminating the need for welding work when installing the shear reinforcement member 18.

[0067] Furthermore, both adjacent tunnel boxes 10 are equipped with a pair of recesses 10b located either vertically or horizontally in the area of ​​the rectangular frame-shaped main girder 11 on the side of the adjacent small-section tunnel 20, and the detachable main girder 11A is fitted into the pair of recesses 10b. Therefore, by smoothly removing the detachable main girder 11A, the adjacent tunnel boxes 10 can be quickly connected to each other.

[0068] Furthermore, because a replacement beam 11B is installed near the area where the detachable main girder 11A was removed, the reduction in rigidity of the tunnel box 10 caused by the removal of the detachable main girder 11A is suppressed.

[0069] Next, an example of a construction method for a large-section tunnel according to this embodiment will be described with reference to Figures 9A to 11B.

[0070] As shown in Figure 9A, a shaft T is constructed to propel the tunnel box 10, and as shown in Figure 9B, a large-section tunnel 100 is constructed using the harmonica method below an existing underground structure S.

[0071] First, a retaining wall D is constructed to surround the construction area. Ground improvement work is then carried out on the ground inside the retaining wall D, and, if necessary, on the ground outside the retaining wall D, to increase the strength of the ground.

[0072] In this way, by improving the ground inside the retaining wall D, as shown in Figures 11A and 11B, the tunnel box 10 at the leading edge in the tunneling direction becomes the cutting box M, and its front is opened, enabling open excavation where the face K ahead is excavated from inside the tunnel box 10. Furthermore, this open excavation allows the use of the guide material 60, which is described below, as there is a concern that it may interfere with the cutter head, etc., when using a closed-type tunnel boring machine.

[0073] Figure 11A illustrates the construction direction when constructing the small-section tunnel 20 located on the upper and lower edges of the rectangular frame-shaped line L. Because it is horizontally elongated and has a low height t2, workers are forced to excavate in a crouched position as shown in the example, and the excavated soil is collected in the soil bucket J and discharged towards the shaft T.

[0074] In contrast, Figure 11B illustrates the construction direction when constructing the small-section tunnel 20 located on the left and right sides of the rectangular frame-shaped line L. Because it is vertically elongated and has a high height t3, workers set up multiple levels of scaffolding E as shown in the example and use each level of scaffolding E to perform excavation. Furthermore, because there is ample workspace, a conveyor belt B can be installed, and the excavated soil can be discharged into a soil bucket J via the conveyor belt B and then removed towards the shaft T.

[0075] When constructing a small-section tunnel 20 by sequentially propelling multiple tunnel boxes 10 into the ground from a shaft T, a guide material 60A is installed below the small-section tunnel where there is no other small-section tunnel below it, as shown in Figure 9B.

[0076] Specifically, since there are no other small-section tunnels below the small-section tunnels 20 provided at the top and bottom edges of the rectangular frame-shaped line L, guide materials 60B made of square pipes or steel pipes are inserted into the ground from the shaft T at these lower positions.

[0077] Here, the construction order of the small-section tunnels 20 in the illustrated example is as shown in Figure 10, for example. Specifically, the three small-section tunnels 20 located on the upper side of the rectangular frame line L are constructed first, then the two small-section tunnels 20 on each side of the rectangular frame line L are constructed in order from top to bottom. Finally, the three small-section tunnels 20 located on the lower side of the rectangular frame line L are constructed.

[0078] Following this construction sequence, guide materials 60A are installed at two locations on the left and right below the central small-section tunnel 20, one of the three small-section tunnels 20 located on the upper edge of the rectangular frame-shaped line L, before the central small-section tunnel 20 is constructed by jacking (Process A).

[0079] Next, regarding the guide materials 60 that guide the jacking of the small-section tunnels 20 located to the left and right of the central small-section tunnel 20, one of the lower left and right guide materials 60A will be used in conjunction with the already installed central guide material 60A, and the other lower left and right guide material 60A will be installed at the position that forms the inside corner with the small-section tunnels 20 on the left and right sides. Then, guided by these guide materials 60A, the small-section tunnels 20 located to the left and right of the upper edge will be jacked up sequentially (Step B).

[0080] This construction method allows the three small-section tunnels 20 at the top to be constructed in a stable position in the predetermined direction, while the two guide members 60A located below them on the left and right sides prevent the direction of tunneling from shifting downward in the direction of gravity.

[0081] Next, two small-section tunnels 20 are constructed sequentially from above on each of the left and right sides of the rectangular frame-shaped line L (all subsequent tunnel jacking construction of the small-section tunnels 20 is in process B). At this time, since there are no other small-section tunnels to the left or right of the small-section tunnels constructed on the sides, two guide materials 60B are installed on the left and right positions below the small-section tunnels when constructing the small-section tunnels 20 on the sides.

[0082] During the construction of the upper small-section tunnel 20 on the side, one guide material 60A at the upper inner corner and two guide materials 60B on the lower left and right ensure that the small-section tunnel 20 is constructed in a stable position in the predetermined direction without shifting laterally.

[0083] Next, when constructing the lower small-section tunnel 20 on the side, two more guide members 60B are installed on the left and right sides below. By using the two guide members 60B already installed on the left and right above, and the two newly installed guide members 60B on the left and right below, the small-section tunnel 20 is constructed in a stable position in the predetermined direction without shifting laterally.

[0084] Finally, two guide materials 60A are installed on the left and right sides below the central small-section tunnel 20 at the bottom of the rectangular frame-shaped line L, and the central small-section tunnel 20 is constructed by jacking while being guided by these guide materials.

[0085] Next, in the construction of the small cross-section tunnels 20 on the left and right sides of the lower edge, the small cross-section tunnels 20 on the left and right sides of the lower edge are constructed while being guided by one guide material 60A located on the central side that has already been constructed, and two guide materials 20B that have already been installed during the construction of the small cross-section tunnels 20 on the left and right sides of the lower edge.

[0086] In the tunnel jacking construction of a small-section tunnel 20 guided by the guide material 60 shown in the illustration, the guide material 60 that is no longer used during the subsequent tunnel jacking construction of the small-section tunnel 20 can be dismantled, removed, and recovered through the open front opening of the tunnel box 10.

[0087] This construction method makes it possible to reuse the removed and recovered guide material 60 as guide material during the construction of subsequent small-section tunnels 20.

[0088] In the example shown in Figure 10, there is an existing structure S above the small-section tunnel 20 on the upper side of the rectangular frame-shaped line L. To prevent settlement of the existing structure S, construction of the upper small-section tunnel 20 is carried out first. Then, inside each interconnected small-section tunnel 20, the axial force transmission members 17 and shear reinforcement members 18, as previously described, are installed, and concrete is poured to increase the rigidity of the three small-section tunnels 20. Subsequently, construction of the small-section tunnels 20 on each side and the small-section tunnel 20 on the lower side is carried out sequentially.

[0089] Here, the construction sequence of each small-section tunnel 20 along the rectangular frame-shaped line L is not limited to the illustrated example. For example, the three small-section tunnels 20 at the bottom edge of the rectangular frame-shaped line L may be constructed first, followed by the two small-section tunnels 20 on each of the left and right sides, and finally the three basic small-section tunnels 20 at the top edge.

[0090] The detachable main girders 11A of both tunnel boxes 10 of the adjacent small-section tunnel 20 are removed, a replacement beam 11B is installed nearby, and a watertight steel plate 33 is installed in the formed recess 10c, thereby forming a watertight structure at the joint between the tunnel boxes 10 (this completes step C).

[0091] Furthermore, other embodiments may be used in which other components are combined with the configurations listed in the above embodiments, and the present invention is not limited in any way to the configurations shown herein. In this regard, modifications can be made without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of Symbols]

[0092] 10: Tunnel box 10A: Ring fitting 10a: Outer shell 10b: Inner end face (recess) 10c: Recess (removal area) 11: Main girder 11A: Detachable main girder (opposing main girder) 13: Skin Plate 15: Vertical ribs 15a: Through hole 16: Shear reinforcement member 17: Axial force transmission member 18: Shear reinforcement member 18a: Shaft member 18b: Fixing section 20: Small-section tunnel 31: Axial waterproofing material 33:Water stop steel plate 35: Water sealing material between rings 50A: Ring joint water stop line 50B: Watertight line between small-section tunnels 60, 60A, 60B: Guide material 90: Corner section 95: Corner reinforcement steel 100: Large-section tunnel G: Ground (underground) L: Rectangular frame line T:Shaft D: Retaining wall S: Existing structure K: Post M: Cutting box E: Scaffolding B: Belt convection J: Bucket of excavated soil

Claims

1. A large-section tunnel is formed by connecting multiple rectangular frame-shaped tunnel boxes in the axial direction of the tunnel via ring joints using a tunneling method or a shield tunneling method, thereby forming small-section tunnels, and then arranging multiple such small-section tunnels side by side along a rectangular frame-shaped line perpendicular to the tunnel axis. The tunnel box comprises a plurality of rectangular frame-shaped main girders arranged at intervals in the axial direction, skin plates attached to the periphery of the plurality of main girders, and longitudinal ribs extending in the axial direction and connecting the plurality of main girders. Both of the adjacent small-section tunnels are equipped with a strip-shaped axial watertight material extending in the axial direction at the inner end face of the outer shell on the ground side of both tunnels. A watertight steel plate is installed across the boundary between the adjacent small-section tunnels. A large-section tunnel characterized in that, in both tunnel boxes, the axial water-sealing material is sandwiched between the inner end face of the outer shell and the water-sealing steel plate.

2. The aforementioned small cross-section tunnel is equipped with a ring-to-ring water-sealing material in the ring joint, The large cross-section tunnel according to claim 1, characterized in that the inter-ring water-sealing material and the axial water-sealing material are continuous.

3. The large-section tunnel according to claim 1, characterized in that the inner end face of the outer shell is the inner end face of a plurality of main girders located on the ground side.

4. The large-section tunnel according to claim 1, characterized in that a common watertight steel plate is attached to a plurality of tunnel boxes connected in the axial direction via the ring joint.

5. The large-section tunnel according to claim 1, characterized in that, among the rectangular frame-shaped main girders, the opposing main girder facing the adjacent small-section tunnel has been removed, and the water-stopping steel plate is attached to the removal area, and a replacement beam is installed near the removal area of ​​the opposing main girder to replace the removed opposing main girder.

6. A construction method for a large-section tunnel, wherein multiple rectangular frame-shaped tunnel boxes are joined together in the axial direction of the tunnel via ring joints using a tunneling method or a shield tunneling method to form small-section tunnels, and multiple such small-section tunnels are arranged side by side along a rectangular frame-shaped line perpendicular to the tunnel axis, The tunnel box comprises a plurality of rectangular frame-shaped main girders arranged at intervals in the axial direction, skin plates and joint plates attached to the periphery of the plurality of main girders, and longitudinal ribs extending in the axial direction to connect the plurality of main girders. Both of the adjacent small-section tunnels are equipped with a strip-shaped axial watertight material extending in the axial direction at the inner end face of the outer shell on the ground side of both tunnels. A watertight steel plate is installed across the boundary between the adjacent small-section tunnels. A method for constructing a large-section tunnel, characterized in that, in both tunnel boxes, the axial water-sealing material is sandwiched between the inner end face of the outer shell and the water-sealing steel plate.

7. A method for constructing a large-section tunnel according to claim 6, characterized in that, among the rectangular frame-shaped main girders, the opposing main girder facing the adjacent small-section tunnel is removed to create a removal area, the watertight steel plate is attached to the removal area, and a replacement beam is installed near the removal area of ​​the opposing main girder to replace the removed opposing main girder.

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