Methods for constructing underground structures

Abstract

This invention provides a method for constructing underground structures where connected widening sections and partially widened sections are adjacent to each other, thereby minimizing constraints on the work processes for each section. [Solution] The process includes a connecting widening step to form a connecting widening section A by linking the parallel-arranged first tunnel 1 and second tunnel 2, and a partial widening step to form a partial widening section C by cutting and widening the first tunnel 1. The connecting widening step includes a connecting space construction step to construct a space S1 in the area between the first tunnel 1 and the second tunnel 2, and in the first base construction step, an inbound / outbound route leading to space S1 is provided inside the second tunnel 2.

Description

Technical Field

[0001] The present invention relates to a method for constructing underground structures.

Background Art

[0002] As a method for constructing a road branch or merging section underground, a method is known in which a connection widening section where two or more parallel tunnels are connected and a partial widening section where a single tunnel is cut and widened are arranged in series in the longitudinal direction of the tunnel (Patent Document 1).

[0003] When excavation work is carried out outside the tunnel when constructing the connection widening section and the partial widening section, auxiliary construction methods such as support work, pipe roofing, ground improvement, and freezing method are often used in combination so that ground collapse and subsidence do not occur.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When working outside the tunnel, it is necessary to secure a space (hereinafter referred to as a "preparation work space") for a construction base outside the tunnel and carry in materials and heavy equipment used for auxiliary construction methods etc. into the preparation work space through the tunnel, and carry out in parallel the work of carrying out the removed lining and earth and sand etc. from the preparation work space to the tunnel. When such work is carried out in both the connection widening section and the partial widening section, if the work process is delayed in one section, there is a risk of affecting the other section.

[0006] The present invention aims to provide a method for constructing an underground structure in which a connected widening section and a partially widening section are adjacent, such that delays in the work process of one section are less likely to affect the other section. [Means for solving the problem]

[0007] The present invention is a method for constructing an underground structure, comprising a connecting widening step of forming a connecting widened section by linking a first tunnel and a second tunnel that are arranged side by side, and a partial widening step of forming a partially widened section by cutting and widening the first tunnel. The aforementioned connecting widening step includes a connecting space construction step that constructs a space in the area between the first tunnel and the second tunnel. Furthermore, an inbound / outbound route leading to the aforementioned space is provided within the second tunnel.

[0008] In this invention, since materials and equipment for constructing the connected widening section are transported to and from the first preparation work space via the second tunnel, the transport of materials and equipment can be carried out smoothly even if the connected widening section and the partial widening section are constructed at the same time. In other words, even if a delay occurs in the work process in one of the connected widening section or the partial widening section, it is unlikely to affect the other section.

[0009] The partial widening process may include a second base construction process for forming at least one second preparatory work space outside the first tunnel, which will serve as a construction base for the construction work of the partial widening section; a pipe roof installation process for pressing a plurality of steel pipes constituting a pipe roof along the first tunnel into the surrounding ground from the second preparatory work space; a lining removal process for removing a portion of the lining of the first tunnel located below the pipe roof from inside the first tunnel; a widening space construction process for constructing a space outside the first tunnel that communicates with the opening formed by the lining removal process; and a widening lining construction process for connecting the widening lining to the remaining lining of the first tunnel. In the connected widening process, when excavation work is performed on the natural ground, the excavated soil can be transported out via the second tunnel. In the partial widening process, when pipe roof installation work is performed, the necessary equipment and materials for the pipe roof installation work can be brought in via the first tunnel, and when excavation work is performed on the natural ground or when lining removal work is performed, the excavated soil and other materials can be transported out via the first tunnel. In other words, according to one preferred embodiment of the present invention, the connected space construction process can be performed in the connected widening section while the pipe roof installation process, lining removal process, widening space construction process, and widening lining construction process can be performed in the partial widening section, thereby shortening the construction period.

[0010] It is preferable to form the horizontal tunnel on the partially widened section side of the boundary between the connected widened section and the partially widened section. In this case, in the connected space construction process, it is preferable to start the excavation work from the horizontal tunnel and alternate between excavating the natural ground and installing support structures. This approach allows for the use of horizontal tunnels in construction work near the boundary between the connected widening section and the partially widened section, thereby shortening the construction period.

[0011] If the excavator shaft used in the construction of the second tunnel is to be left in place: ,before It is preferable to use the opening provided in the body section to form the horizontal shaft. Since the excavator's body is typically made of steel, openings can be easily formed by gas cutting or other methods.

[0012] In the pipe roof installation process, it is preferable to press-fit at least one of the steel pipes to a position where it intersects with the horizontal shaft. In this way, even when constructing a widened space in a section of widening adjacent to a horizontal tunnel, ground deformation associated with excavation can be suppressed.

[0013] Furthermore, in the second base construction process, if a second preparatory work space is to be provided near the boundary between the connected widening section and the partially widened section, it is preferable to perform the second base construction process (the work of constructing the second preparatory work space) after the excavator for the second tunnel has reached the vicinity of the boundary between the connected widening section and the partially widened section, so as not to affect the construction work of the second tunnel or the construction work of the side tunnel. On the other hand, if the second base construction process involves forming the second preparatory work space on the partially widened section side of the horizontal tunnel, and the steel pipes are pressed in from the second preparatory work space toward the boundary during the pipe roof installation process, the second base construction process can be carried out before the excavator for the second tunnel reaches the vicinity of the boundary between the connected widened section and the partially widened section, thereby shortening the construction period.

[0014] If the excavator used in the construction of the second tunnel is to be left in place, it is preferable to press at least one of the steel pipes into the faceplate of the excavator during the pipe roof installation process. In this way, even when constructing a widened space in a section of the tunnel close to the excavator of the second tunnel, ground deformation associated with excavation can be suppressed.

[0015] If the excavator used in the construction of the second tunnel is to be left in place, it is preferable to perform a second partial widening step after the partial widening step, in which the lining of the first tunnel adjacent to the excavator and at least a portion of the excavator's body are removed, and the widening lining is connected to the remaining lining of the first tunnel. In this way, even if the excavator for the second tunnel is left in place, the first tunnel can be widened in the area adjacent to the excavator.

[0016] In the second base construction process, it is preferable to form multiple second preparation work spaces at positions offset from the first tunnel in both the circumferential and longitudinal directions. This approach allows for smaller second-stage preparation work spaces, thereby reducing the risk of ground deformation. When forming a plurality of secondary preparation work spaces, it is preferable to form a pilot tunnel connecting the secondary preparation work spaces to each other. By doing so, since it is only necessary to communicate any one of the plurality of secondary preparation work spaces with the first tunnel (that is, it is only necessary to provide one opening in the first tunnel), the influence on the strength of the first tunnel can be reduced.

[0017] At the boundary between the connection widening section and the partial widening section, it is preferable to perform a boundary construction process. In the boundary construction process, it is preferable to form a gusset wall of the connection widening section. Forming a gusset wall at the boundary between the connection widening section and the partial widening section enhances the strength of the structural change part and can suppress the occurrence of water leakage.

Advantages of the Invention

[0018] According to the present invention, when constructing a subterranean structure in which a connection widening section and a partial widening section are adjacent to each other, even if a delay occurs in the working process of one section, it is difficult for the other section to be affected.

Brief Description of the Drawings

[0019] [Figure 1] It is a plan view showing a subterranean structure according to an embodiment. [Figure 2] (a) is a cross-sectional view of the connection widening section (cross-sectional view taken along line 2A - 2A of FIG. 1), (b) is a cross-sectional view of the switching section (cross-sectional view taken along line 2B - 2B of FIG. 1), (c) is a cross-sectional view of the partial widening section (cross-sectional view taken along line 2C - 2C of FIG. 1) [Figure 3] It is a flowchart for explaining a method of constructing a subterranean structure according to an embodiment. [Figure 4] It is a plan view for explaining the connection widening process. [Figure 5] (a) is a cross-sectional view taken along line 5A - 5A of FIG. 4 in the widening process, (b) is also a cross-sectional view taken along line 5B - 5B of FIG. 4, (c) is also a cross-sectional view taken along line 5C - 5C of FIG. 4, (d) is also a cross-sectional view taken along line 5D - 5D of FIG. 4. [Figure 6] It is an enlarged cross-sectional view of the switching section. [Figure 7](a) is a longitudinal section of the shaft, which is the first work preparation space, and (b) is a transverse section. [Figure 8] This is a flowchart of the shaft construction process. [Figure 9] (a) is a plan view illustrating the construction process of the second base according to the modified example, (b) is a cross-sectional view of (a) between 9B and 9B, and (c) is a cross-sectional view of (a) between 9C and 9C. [Modes for carrying out the invention]

[0020] As an embodiment of the present invention, an underground structure 100 that forms a road junction or merging point is given as an example. As shown in Figure 1, the underground structure 100 comprises a connecting widening section A that connects the first tunnel 1 and the second tunnel 2, a partial widening section C that is created by cutting and widening the first tunnel 1, and a switching section B provided between the connecting widening section A and the partial widening section C.

[0021] Tunnel 1 is a main tunnel that encloses the main road. The second tunnel (2) is a ramp tunnel that encloses a merging lane that joins the main line or a diverging lane that branches off from the main line, and is located next to the first tunnel (1). Tunnel 1 and Tunnel 2 are shield tunnels (tunnels constructed using the shield tunneling method). However, Tunnel 1 and Tunnel 2 may also be tunnels constructed using methods other than the shield tunneling method (for example, tunnels constructed using the pipe jacking method).

[0022] As shown in Figure 2(a), the connected widening section A is a section with an interior area larger than the combined interior area of ​​the first tunnel 1 and the second tunnel 2. The connected widening section A has a large-section lining 101 that connects the first tunnel 1 and the second tunnel 2. The large-section lining 101 comprises the lining of the first tunnel 1 (main line lining 11), the lining of the second tunnel 2 (ramp lining 21), and connecting linings 12 and 13 that span the space between the first tunnel 1 and the second tunnel 2.

[0023] As shown in Figure 2(c), the partially widened section C has an internal area that is larger than the internal area of ​​the first tunnel 1 and smaller than the internal area of ​​the connected widened section A. Partially widened section C has a small cross-section lining 102 formed using the first tunnel 1. The small cross-section lining 102 comprises the lining of the first tunnel 1 (main line lining 11) and a widening lining 14 added to the outside of the first tunnel 1.

[0024] As shown in Figure 2(b), the transition section B is the section (boundary) where the lining extending from the lining of the connected widening section A and the lining extending from the lining of the partial widening section C overlap. A boundary section 3 is formed in the transition section B. That is, the underground structure 100 has a boundary section 3 provided between the large-section lining 101 and the small-section lining 102. The boundary section 3 is equipped with a fascia wall 33. The fascia wall 33 is a wall that closes the opening resulting from the difference in cross-sectional shape between the connected widening section A and the partial widening section C.

[0025] The construction method for the underground structure 100 includes, as shown in Figure 3, "1. Tunnel construction process," "2. Widening process," and "3. Boundary construction process."

[0026] <1. Tunnel Construction Process> The tunnel construction process involves constructing multiple tunnels. The tunnel construction process in this embodiment includes "1.1 First Tunnel Construction Process" and "1.2 Second Tunnel Construction Process". The first tunnel construction process involves constructing the first tunnel 1 for the main line in at least the connecting widening section A, the switching section B, and the partial widening section C. The second tunnel construction process involves constructing a second tunnel 2 for ramps in at least the connecting widening section A and the switching section B. In this embodiment, the first tunnel 1 and the second tunnel 2 are constructed using the shield tunneling method. There are no restrictions on the type of segments that make up the lining of the first tunnel 1 (main line lining 11) and the lining of the second tunnel 2 (ramp lining 21), but in this embodiment, steel segments 43 (see Figure 7) are used. As shown in Figures 4 and 5(a) and (b), in the connecting widening section A and the switching section B, the first tunnel 1 and the second tunnel 2 are installed side by side with a gap in between. In the second tunnel construction process, the excavator shell 22 used for the construction of the second tunnel 2 is left in place. In this embodiment, the excavator is advanced along the first tunnel 1 until the entire excavator is beyond the switching section B. After removing the equipment inside the excavator (faceplate drive device, erector, propulsion jacks, etc.), the shell 22 is left in place to the side of the first tunnel 1. Furthermore, the construction process for the first tunnel and the construction process for the second tunnel may be carried out either one first or simultaneously.

[0027] <2. Widening Process> The widening process is the process of widening at least one of several tunnels. In this embodiment, the widening process includes "2.1 Connecting widening process," "2.2 First partial widening process," and "2.3 Second partial widening process," as shown in Figure 3.

[0028] <2.1 Connecting and widening process> The connecting widening process is the process of constructing the connecting widening section A. In other words, the connecting widening process is the process of connecting the first tunnel 1 and the second tunnel 2 to form a single structure. The connecting widening process in this embodiment includes (1) the first base construction process, (2) the connecting space construction process, (3) the first widening lining construction process, and (4) the first lining removal process.

[0029] (1) First base construction process The first base construction process involves forming at least one first preparatory work space S1 outside the first tunnel 1 and the second tunnel 2, as shown in Figures 4 and 5(a) and (b). The first preparatory work space S1 will serve as a construction base used for the construction of the connected widening section A. In the first base construction process, an access route to the first preparatory work space S1 is provided inside the second tunnel 2. In this embodiment, an opening leading to the first preparation work space S1 is provided in the excavator's body 22. Since the body 22 is usually made of steel, the opening can be easily formed by gas cutting or the like. When bringing materials and equipment into the first preparation work space S1, the materials and equipment are first brought into the excavator body 22 from the portal of the second tunnel 2 (not shown), and then brought into the first preparation work space S1 using a lifting device or hoisting device (not shown) installed to match the opening of the body 22. When removing materials, equipment, and excavated soil from the first preparation work space S1, they are first removed into the body 22 through the opening of the body 22, and then removed to the portal of the second tunnel 2 (not shown).

[0030] The first preparation workspace S1 of this embodiment comprises a horizontal shaft S11 and vertical shafts S12, S12. The horizontal shaft S11 extends in a direction that transverses the first tunnel 1 and the second tunnel 2. The vertical shafts S12, S12 extend in the longitudinal direction of the first tunnel 1 and the second tunnel 2.

[0031] As shown in Figure 4, the horizontal tunnel S11 is formed on the partially widened section C side of the switching section B (the boundary between the connected widened section A and the partially widened section C). As shown in Figure 5(b), the outer surfaces of the first tunnel 1 and the second tunnel 2 are exposed in the horizontal tunnel S11. The horizontal tunnel S11 is supported by steel supports and shotcrete. The process of constructing the horizontal tunnel (horizontal tunnel construction process) includes the work of forming an opening in the excavator's body 22, excavating the ground surrounding the body 22 from the opening in the body 22 to form the entrance portion of the horizontal tunnel S11 on the outside of the body 22, and extending the horizontal tunnel S11 to directly above the first tunnel 1 while supporting the ground exposed in the horizontal tunnel S11 with steel supports and shotcrete.

[0032] As shown in Figure 4, the vertical shafts S12, S12 are formed on the side of the connecting widening section A that is closer to the horizontal shaft S11, and are used as a space (preparation work space) for carrying out various operations after the connecting space construction process. As shown in Figure 5(a), the outer surface of the first tunnel 1 is exposed in one vertical shaft S12, and the outer surface of the second tunnel 2 is exposed in the other vertical shaft S12. The vertical shaft S12 will be constructed from the horizontal shaft S11 towards the starting end of the connecting widening section A (the end opposite to the switching section B). Details of the process for constructing the vertical shaft S12 (vertical shaft construction process) will be described later.

[0033] (2) Connected space construction process The connecting space construction process is the process of constructing a space (connecting space V1) in the area between the first tunnel 1 and the second tunnel 2. In this embodiment, the connecting space V1 is a space adjacent to the outer surface of the shield tunnel (first tunnel 1 and second tunnel 2) and adjacent to the vertical shaft S12 (first preparation work space S1). In the upper half of the connected widening section A, excavation work begins in the area between the vertical shafts S12, S12, starting from the horizontal shaft S11 (see Figure 4). Subsequently, the process alternates between excavating the area adjacent to the outer surface of the shield tunnel and adjacent to the vertical shaft S12 (main excavation process) and installing support structures (second support members 52 in this embodiment) along the top surface of the space formed by the excavation (second support process). Details of the second support process will be described later. In the lower half of the connected widening section A, the process of excavating the natural ground in the area between the first tunnel 1 and the second tunnel 2 is carried out alternately, as is the process of erecting support members between the first tunnel 1 and the second tunnel 2.

[0034] (3) Construction process of the first widening and covering The first widening lining construction process involves connecting arch-shaped connecting linings 12 and 13 (see Figure 2(a)) to the linings of the first tunnel 1 and the second tunnel 2. The connecting linings 12 and 13 are installed below the second support member 52 so as to straddle the area (connecting space V1) sandwiched between the first tunnel 1 and the second tunnel 2. One end of the connecting linings 12 and 13 is connected to the lining of the first tunnel 1, and the other end of the connecting linings 12 and 13 is connected to the lining of the second tunnel 2. The connecting linings 12 and 13 may be formed by placing a centering (not shown) in the connecting space V1 and pouring concrete between the centering and the ground, or by assembling segments similar to those for shield tunnels within the connecting space V1.

[0035] (4) First lining removal process The first tunnel lining removal process involves removing the lining of the first tunnel 1, which does not face the ground, below the upper connecting lining 12, and also removing the lining of the second tunnel 2, which does not face the ground.

[0036] <2.2 First Partial Widening Process> The first partial widening process is the process of constructing the partially widened section C. That is, the first partial widening process is the process of forming a structure by widening the first tunnel 1. The first partial widening process in this embodiment includes (1) the second base construction process, (2) the pipe roof installation process, (3) the second lining removal process, (4) the widening space construction process, and (5) the second widening lining construction process.

[0037] (1) Second base construction process The second base construction process involves forming at least one second preparatory work space S2 outside the first tunnel 1, as shown in Figure 5(d). The second preparatory work space S2 will serve as a construction base used for the construction of the partially widened section C. The second preparatory work space S2 shown in Figure 5(d) is a horizontal tunnel extending in a direction intersecting the first tunnel 1. In the second base construction process, an access route to the second preparatory work space S2 is provided within the first tunnel 1. As shown in Figure 4, in this embodiment, the second preparatory work space S2 is formed on the partially widened section C side of the horizontal tunnel S11 (on the partially widened section C side of the switching section B). When the second preparatory work space S2 is formed at a location away from the horizontal tunnel S11, the second base construction process can be carried out before the excavator of the second tunnel 2 reaches the switching section B (near the boundary between the connected widened section A and the partially widened section C), thus shortening the construction period.

[0038] (2) Pipe roof installation process The pipe roof installation process is the process of forming a pipe roof 15 above the first tunnel 1. As shown in Figure 5(c), in the pipe roof installation process, multiple steel pipes constituting the pipe roof 15 are pressed into the surrounding ground of the first tunnel 1. In the pipe roof installation process of this embodiment, the second preparation work space S2 (see Figure 5(d)) is used as the construction base for the pipe roof method, and steel pipes are pressed in from the second preparation work space S2 toward the switching section B. As shown in Figure 4, in this embodiment, at least one steel pipe is pressed in up to just before the horizontal shaft S11, and at least one steel pipe is pressed in above the body 22 to a position beyond the faceplate of the excavator. In this way, even when the second excavation process is carried out in the horizontal shaft S11 and the partially widened section C close to the excavator, ground deformation associated with excavation can be suppressed.

[0039] Although the pipe roof installation process may be carried out after the horizontal tunnel S11 is constructed, if there is a risk of the pipe roof 15 interfering with the steel support structure of the horizontal tunnel S11 upon arrival, it is preferable to construct the horizontal tunnel S11 after the pipe roof installation process is carried out.

[0040] (3) Second lining removal process The second lining removal process involves removing a portion of the lining of the first tunnel 1, located beneath the pipe roof 15, from inside the first tunnel 1. Prior to the second lining removal process, ground improvement or freezing may be carried out on the surrounding ground of the first tunnel 1.

[0041] (4) Process for constructing the widened space The widening space construction process is a process of constructing a space (widening space V2) on the outside of the first tunnel 1 that is in communication with the opening formed by the second lining removal process. In the widening space construction process, the exposed ground due to the removal of the lining is excavated from the inside of the first tunnel 1 toward the outside, forming a widening space V2 that is in communication with the interior of the first tunnel 1, as shown in Figure 2(c).

[0042] (5) Construction process for the second widening and covering The second widening lining construction process involves connecting the widening lining 14 to the remaining lining 11 of the first tunnel 1.

[0043] Furthermore, the second lining removal process, the second excavation process, and the second widening lining construction process may be repeated for every one or several rings of the first tunnel 1. Alternatively, the second lining removal process may be carried out over the entire length of the partial widening section C, followed by the second excavation process over the entire length of the partial widening section C, and then the second widening lining construction process over the entire length of the partial widening section C.

[0044] <2.3 Second Partial Widening Process> The second partial widening step is the step of constructing a partially widened section C in the area adjacent to the excavator's shell 22. The second partial widening step is preferably performed after the first partial widening step. In the second partial widening step of this embodiment, at least a portion of the lining of the first tunnel 1 adjacent to the excavator's shell 22 and the excavator's shell 22 are removed, and the widening lining 14 is connected to the remaining lining of the first tunnel 1.

[0045] <3 Boundary construction process> The boundary construction process is the process of forming the boundary section 3 in the switching section B. As shown in Figure 2(b), the boundary section 3 comprises an outer shell 31, an inner shell 32, and a fascia wall 33.

[0046] The outer shell 31 is connected to the lining (large-section lining 101) of the connecting widening section A. In this embodiment, the outer shell 31 is an extension of the large-section lining 101 to the partially widened section C. That is, the outer shell 31 in this embodiment is formed by the lining (main line lining 11) left in the first tunnel 1, the lining (ramp lining 21) left in the second tunnel 2, and the connecting linings 12 and 13. In this embodiment, the main line lining 11, ramp lining 21, and connecting linings 12 and 13 are made of steel segments. The inner shell 32 is connected to the lining (small-section lining 102) of the partially widened section C within the outer shell 31. In this embodiment, the inner shell 32 is an extension of the small-section lining 102 to the connected widened section A. That is, the inner shell 32 in this embodiment is formed by a part of the main line lining 11 and the widening lining 14.

[0047] In this embodiment, the case in which the outer shell 31 and inner shell 32 are lining segments is illustrated, but the portion of the outer shell 31 extending from the connecting linings 12 and 13, and the portion of the inner shell 32 extending from the widening lining 14, may use wooden or steel concrete formwork instead of lining segments.

[0048] The fascia wall 33 is formed in the region enclosed by the outer shell 31 and the inner shell 32. That is, the fascia wall 33 is formed inside the outer shell 31 and outside the inner shell 32. The fascia wall 33 in this embodiment includes a concrete section cast using the outer shell 31 and the inner shell 32 as formwork. The outer shell 31 and the inner shell 32 have anchoring members (e.g., dowels, longitudinal ribs of steel segments, etc.) that are fixed to the concrete section. In this way, the outer shell 31 and the concrete section are integrated, and the inner shell 32 and the concrete section are integrated, thereby improving the watertightness of the fascia wall 33.

[0049] As shown in Figure 6, the fascia wall 33 has tunnel circumferential reinforcement 33a and tunnel axial reinforcement 33b arranged along the outer shell 31, and tunnel radial reinforcement 33c arranged in a direction intersecting the tunnel circumferential reinforcement 33a and tunnel axial reinforcement 33b. The tunnel radial reinforcement 33c is inserted between adjacent longitudinal ribs in the circumferential direction in the steel segment 43 that constitutes the outer shell 31. In this way, the fascia wall 33 becomes a steel-concrete composite structure with the steel segment 43 as the steel shell, thereby increasing the durability of the boundary section 3.

[0050] Although not shown in the diagram, the boundary section 3 includes an outer waterproofing member that seals the gap between the outer shell 31 and the fascia wall 33, and an inner waterproofing member that seals the gap between the inner shell 32 and the fascia wall 33. The outer waterproofing member is, for example, a water-swellable sealing material, and is bonded to the inner circumferential surface of the outer shell 31 (in this embodiment, the inner circumferential end surface of the main girder of the steel segment) at the boundary between the switching section B and the partially widened section C. The internal water-sealing member is, for example, a water-swellable sealing material, and is bonded to the outer surface of the inner shell 32 at the boundary between the switching section B and the partially widened section C.

[0051] In the boundary construction process, first, an outer formwork is installed at the boundary between the switching section B and the partially widened section C, closing the opening at the end face of the connecting widened section A. An outer waterproofing member is attached to the inner circumferential surface of the outer shell 31, and an inner waterproofing member is attached to the outer circumferential surface of the inner shell 32. Next, tunnel circumferential reinforcement 33a, tunnel axial reinforcement 33b, and tunnel radial reinforcement 33c are arranged. Subsequently, an inner formwork is installed opposite the outer formwork. After that, concrete is poured into the space enclosed by the outer shell 31, inner shell 32, outer formwork, and inner formwork. Once the concrete reaches its demolding strength, the inner formwork is demolded. Note that the horizontal tunnel S11 can also be used in the boundary construction process, thus shortening the construction period.

[0052] <Vertical shaft construction process> The vertical shaft construction process, which is included in "(1) First Base Construction Process" of "2.1 Connecting and Widening Process" shown in Figure 3, will be described in detail below.

[0053] As shown in Figure 7(b), the shaft S12 is an advanced pilot tunnel supported by a first support member 41 and shotcrete. The first support member 41 is a steel support structure and is supported by the lining of either the first tunnel 1 or the second tunnel 2. As shown in Figure 7(a), the first support member 41 is positioned in accordance with the main girder 43a of the steel segment 43 that constitutes the lining of either the first tunnel 1 or the second tunnel 2. In this embodiment, the first support member 41 is positioned where adjacent steel segments 43, 43 in the tunnel axial direction abut against each other, and the lower end of the first support member 41 is fixed to the skin plate 43b by welding. That is, the force acting on the first support member 41 is ultimately transmitted to the main girder 43a of the steel segment 43.

[0054] Inside the vertical shaft S12, support legs 51, support girders 53, brackets 54, intermediate girders 55, weir plates 56, and filling material 57 are arranged.

[0055] The support leg 51 is an arch-shaped member that receives the axial force of the second support member 52. In this embodiment, the support leg 51 is made of steel (such as H-beams or I-beams). The support leg 51 is joined to the support girder 53 between adjacent first support members 41, 41 in the longitudinal direction of the support girder 53.

[0056] The support girder 53 is a girder that extends in a direction intersecting the first support member 41. The lower end of the support leg 51 is joined to the support girder 53. The support girder 53 is positioned at the joint between the lining of the first tunnel 1 or the lining of the second tunnel 2 and the first support member 41, and is supported by the lining and the first support member 41. It is preferable that the support girder 53 abuts against the inner surfaces of at least two first support members 41 that are arranged in parallel in the tunnel axis direction. The support girder 53 in this embodiment is made of steel (such as H-beams or I-beams). By providing the support girder 53 and having the support leg 51 supported by the support girder 53, even if the support leg 51 cannot be installed in accordance with the main girder 43a of the steel segment 43, the support point of the support leg 51 is stabilized, thereby increasing the stability of the second support member 52 supported by the support leg 51, and consequently suppressing deformation of the surrounding ground in the connecting space V1.

[0057] The bracket 54 is a member that supports the intermediate girder 55 and is fixed to the first support member 41. In this embodiment, the bracket 54 protrudes from the first support member 41 towards the internal space of the shaft S12.

[0058] The intermediate girder 55 is a girder member that extends in a direction intersecting the first support member 41. The upper ends of the support legs 51 are placed on the intermediate girder 55. The intermediate girder 55 is placed on brackets 54 and is supported by the first support member 41 via brackets 54. Preferably, the intermediate girder 55 is spanned across at least two brackets 54, 54 that are arranged side by side in the tunnel axial direction. In this embodiment, the intermediate girder 55 is made of steel (such as H-beams or I-beams).

[0059] The bracket 54 may be omitted, and the intermediate girder 55 may be directly fixed to the first support member 41. Alternatively, if the support legs 51 are positioned in accordance with the position of the main girder 43a of the steel segment 43 (for example, if the support legs 51 are positioned in accordance with the position of the first support member 41, or if the support legs 51 are positioned in accordance with the position of the main girder 43a between adjacent first support members 41, 41 in the tunnel axial direction (the direction of extension of the vertical shaft S12)), the support girder 53, bracket 54, and intermediate girder 55 may be omitted, and the support legs 51 may be directly fixed to at least one of the first support member 41 and the skin plate 43b. In this case, the second support member 52 may be joined to the first support member 41, and the first support member 41 may be interposed between the support legs 51 and the second support member 52.

[0060] The weir plate 56 is a plate material that serves as a formwork when filling the space on the rear side of the support legs 51 with filler material 57, and is installed so as to cover the space between adjacent support legs 51, 51 in the extending direction of the vertical shaft S12. In this embodiment, the weir plate 56 is placed on the upper surface of the support legs 51.

[0061] The filling material 57 is filled into the interior of the vertical shaft S12 above the weir plate 56. The filling material 57 consists of concrete, mortar, or fluidized soil having a strength equal to or greater than that of the surrounding ground. By filling the interior of the vertical shaft S12 above the weir plate 56 with the filling material 57, the stability of the support legs 51 is increased, and consequently, the stability of the second support members 52 supported by the support legs 51 is increased. As a result, the stability of the arch formed by connecting the support legs 51 and the second support members 52 is increased, and deformation of the surrounding ground can be suppressed.

[0062] The shaft construction process is included in the first base construction process in the connecting widening process (see Figure 3). As shown in Figure 8, the shaft construction process includes the advanced excavation process, the first support process, the shotcrete process, the girder installation process, the support leg installation process, the weir plate installation process, and the filling process.

[0063] The advanced excavation process, as shown in Figures 4 and 5(a), involves excavating the ground from the horizontal shaft S11 towards the starting point of the connecting widening section A above either the first tunnel 1 or the second tunnel 2, thereby forming the first preparatory work space S1 (vertical shaft S12) adjacent to either the first tunnel 1 or the second tunnel 2. The first support process involves installing the first support member 41 (see Figure 7) along the ground exposed by the advanced excavation process. By positioning the first support member 41, deformation occurring on the inner wall surface of the shaft S12 due to soil and water pressure from the surrounding ground can be suppressed. In the first support process, as shown in Figure 7(a), the first support member 41 is positioned in accordance with the position of the main girder 43a (main structure of the segment ring) of the steel segment 43 that constitutes the shield tunnel. By positioning the first support member 41 in accordance with the main girder 43a of the steel segment 43, the force acting on the first support member 41 can be transmitted to the main girder 43a of the steel segment 43. By supporting the first support member 41 with the main girder 43a of the steel segment 43, the support point of the first support member 41 is stabilized, and deformation occurring on the inner wall surface of the shaft S12 can be effectively suppressed.

[0064] The spraying process involves spraying concrete onto the exposed ground (the inner wall surface of the shaft S12) as a result of the advanced excavation process. By spraying concrete onto the inner wall surface of the shaft S12, deformation occurring on the inner wall surface of the shaft S12 can be suppressed more effectively. The advanced excavation process, the first support process, and the shotcrete process may be repeated for every ring or several rings of the first tunnel 1 or the second tunnel 2. Alternatively, the advanced excavation process and the first support process may be performed alternately to form the vertical shaft S12 along the entire length of the connected widening section A, after which the shotcrete process may be performed. Alternatively, the advanced excavation process may be performed along the entire length of the connected widening section A, followed by the first support process and the shotcrete process in sequence.

[0065] The girder installation process, as shown in Figure 7(b), involves positioning the support girder 53, bracket 54, and intermediate girder 55 in predetermined locations within the shaft S12.

[0066] The support leg installation process involves installing the support legs 51 inside the vertical shaft S12. In the support leg installation process of this embodiment, the support legs 51 are positioned between adjacent first support members 41, 41 in the longitudinal direction of the support girder 53. The upper end of the support leg 51 is placed on the intermediate girder 55, and the lower end of the support leg 51 is joined to the support girder 53. By supporting the support legs 51 with the support girder 53 and the intermediate girder 55, the force acting on the support legs 51 is transmitted to the main girder 43a of the steel segment 43 via the first support members 41, resulting in a stable structure.

[0067] The weir plate installation process involves installing a weir plate 56 so as to cover at least two support legs 51 that are arranged in parallel in the extending direction of the vertical shaft S12. In the weir plate installation process, the weir plate 56 is installed on the back side of the support legs 51.

[0068] The filling process involves filling the space between the first support member 41 and the support leg 51 with filler material 57. In the filling process of this embodiment, the filler material 57 is filled into the space inside the vertical shaft S12 above the weir plate 56. Once the filler material 57 has achieved the required strength, proceed to "(2) First excavation process" of "2.1 Connecting widening process" shown in Figure 3.

[0069] <Second shoring process> The second support process, which is included in "(2) Construction of connecting space" of "2.1 Connecting widening process" shown in Figure 3, will be described in detail below. Here, the connecting space construction process is performed after the advanced excavation process and takes place in an area adjacent to the pilot shaft S12. In other words, as shown in Figure 5(a), the connecting space construction process is the process of forming a connecting space V1 between the first tunnel 1 and the second tunnel 2.

[0070] The second support process, included in the connecting space construction process, is the process of installing the second support member 52 along the ground exposed by the main excavation process. The second support member 52 is an arch-shaped temporary member that follows the top surface of the arc-shaped cross-section of the connecting space V1 (=main work space) formed by the main excavation process. In this embodiment, the second support member 52 is made of steel (such as H-beams or I-beams). The end face of the second support member 52 is joined to the upper end face of the support leg 51 that has been installed in advance. The support leg 51 in the shaft S12 becomes the base for the second support member 52, making the installation of the second support member 52 easier. In addition, the second support member 52 and the support legs 51, 51 provided on both sides thereof form a series of arches and play a role in suppressing the deformation of the ground exposed by the main excavation process. In this way, since the second support member 52 is positioned within the connecting space V1 (main working space) formed on the outside of the shield tunnel, deformation occurring on the inner wall surface of the connecting space V1 due to the soil and water pressure of the surrounding ground can be suppressed. Once the second shoring process is carried out in at least a portion of the connected widening section A, proceed to "(3) First widening lining construction process" of "2.1 Connected Widening Process" shown in Figure 3.

[0071] <Effects and Effects of the Method for Constructing Underground Structures According to This Embodiment> As described above, according to the method for constructing underground structures according to the embodiment, materials and equipment for constructing the connected widening section A are transported to and from the construction base outside the second tunnel 2 via the second tunnel 2, and materials and equipment for constructing the partial widening section C are transported to and from the construction base outside the first tunnel 1 via the first tunnel 1. Therefore, even if the connected widening section A and the partial widening section C are constructed at the same time, the transport of materials and equipment can be carried out smoothly.

[0072] Furthermore, since the construction of the connecting space can be carried out in the connected widening section A while the pipe roof installation process, lining removal process, widening space construction process, and widening lining construction process can be carried out in the partial widening section C, the construction period can be shortened.

[0073] Furthermore, according to the construction method of the underground structure according to this embodiment, the vertical shaft S12 formed outside the first tunnel 1 and the second tunnel 2 is supported by the first support member 41, so that deformation occurring on the inner wall surface of the vertical shaft S12 due to the soil and water pressure of the surrounding ground can be suppressed. Moreover, since the first support member 41 is positioned in accordance with the main girder 43a (main structure of the segment ring) of the steel segment 43, the force acting on the first support member 41 can be transmitted to the first tunnel 1 and the second tunnel 2. By supporting the first support member 41 on the main girder 43a of the steel segment 43, the support point of the first support member 41 is stabilized, so that deformation occurring on the inner wall surface of the vertical shaft S12 can be effectively suppressed.

[0074] According to the underground structure 100, a gable wall 33 is formed at the boundary 3, and an outer waterproofing member is placed between the outer shell 31 and the gable wall 33, and an inner waterproofing member is placed between the inner shell 32 and the gable wall 33, thereby improving the waterproofing at the boundary between the large-section lining 101 and the small-section lining 102.

[0075] <Example 1> Each step and structure in the above-described embodiment may be modified as appropriate depending on the construction conditions, etc. For example, in the embodiment described above, the case where there is one second preparation workspace S2 is illustrated, but as shown in Figure 9, in the second base construction process, multiple second preparation workspaces S2 may be formed at positions offset in the circumferential and longitudinal directions of the first tunnel 1. In this case, it is preferable to form a pilot tunnel S21 connecting the second preparation workspaces S2, S2. This reduces the size of each second preparation work space S2, thereby suppressing ground deformation and deformation of the first tunnel 1.

[0076] <Modification 2> In the embodiment described above, an example was given in which the first support member 41 is positioned in accordance with the position of the main girder 43a of the steel segment 43. However, the first support member 41 may be positioned at a location offset from the main girder 43a. In this case, it is preferable to position the support legs 51 in accordance with the position of the main girder 32a of the steel segment 43, and to position a support girder so as to connect the lower ends of adjacent support legs 51, 51 in the tunnel axial direction, and to support the first support member 41 with this support girder. Positioning the support legs 51 in accordance with the position of the main girder 43a of the steel segment 43 stabilizes the fulcrum of the support legs 51, thereby increasing the stability of the second support member 52 supported by the support legs 51, and suppressing deformation on the inner wall surface of the main working space (connecting space V1) formed by this excavation process. Furthermore, by providing a support girder and having the first support member 41 supported by the support girder, even if the first support member 41 cannot be installed in accordance with the main girder 43a of the steel segment 43, the support point of the first support member 41 will be stable, thereby suppressing deformation of the surrounding ground of the vertical shaft S12. [Explanation of Symbols]

[0077] 100 Underground structures 101 Large-section lining 102 Small section lining A Widening section B Switching section C Section (Wide-out section) 1. First Tunnel (First Shield Tunnel) 11. Lining (Main line lining) 12,13 Connection lining 14. Widening lining 15 Pipe roof 2. Second Tunnel (Second Shield Tunnel) 21. Treading (ramp lining) 22 Torso 3. Boundary S1 First preparation work space S11 Side shaft S12 Shaft V1 connection space S2 Second preparation work space V2 Widening Space 31 Outer shell 32 Inner shell 33 Sleeve wall 33a Tunnel circumferential reinforcement 33b Tunnel axial reinforcement 33c Tunnel radial reinforcement 41 First support member 43 Steel segments 43a Main girder 43b Skin Plate 51 Support leg 52 Second support member 53 Support beam 54 Brackets 55 Middle digits 56 Weir board 57 Filling material

Claims

1. The process of connecting and widening the tunnels, which are laid out side by side, forms a connected widening section, A method for constructing an underground structure, comprising a partial widening step of forming a partially widened section by cutting and widening the first tunnel, The aforementioned connecting widening step includes a connecting space construction step that constructs a space in the area between the first tunnel and the second tunnel, A transport route leading to the aforementioned space is provided within the second tunnel. A horizontal tunnel is formed on the side of the partial widening section that is further than the boundary between the connected widening section and the partial widening section. In the aforementioned connecting space construction process, excavation work is started from the horizontal tunnel, and the work of excavating the natural ground and the work of installing support structures are performed alternately. The excavator shaft used in the construction of the second tunnel was left in place. A method for constructing an underground structure, characterized by forming the horizontal tunnel using an opening provided in the body portion.

2. A connecting widening step that forms a connecting widening section by connecting the first tunnel and the second tunnel which are arranged side by side, A method for constructing an underground structure, comprising a partial widening step of forming a partially widened section by cutting and widening the first tunnel, The aforementioned connecting widening step includes a connecting space construction step that constructs a space in the area between the first tunnel and the second tunnel, A transport route leading to the aforementioned space is provided within the second tunnel. A horizontal tunnel is formed on the side of the partial widening section that is further than the boundary between the connected widening section and the partial widening section. In the aforementioned connecting space construction process, excavation work is started from the horizontal tunnel, and the work of excavating the natural ground and the work of installing support structures are carried out alternately. The partial widening process includes: a second base construction process for forming at least one second preparatory work space outside the first tunnel, which will serve as a construction base for the construction work of the partial widening section; a pipe roof installation process for pressing a plurality of steel pipes constituting a pipe roof along the first tunnel into the surrounding ground of the first tunnel from the second preparatory work space; a lining removal process for removing a portion of the lining of the first tunnel located below the pipe roof from inside the first tunnel; a widening space construction process for constructing a space outside the first tunnel that communicates with the opening formed by the lining removal process; and a widening lining construction process for connecting the widening lining to the remaining lining of the first tunnel. The excavator used in the construction of the second tunnel was left in place. The method for constructing an underground structure according to the description, characterized in that, in the pipe roof installation step, at least one of the steel pipes is pressed into place up to a position where it intersects with the horizontal shaft, and at least one of the steel pipes is pressed into place up to the faceplate of the excavator.

3. In the second base construction process, the second preparation work space is formed on the side of the partially widened section that is closer to the horizontal tunnel. The method for constructing an underground structure according to claim 2, characterized in that, in the pipe roof installation step, the steel pipe is pressed in from the second preparation work space toward the boundary.

4. The method for constructing an underground structure according to claim 2, characterized in that, in the pipe roof installation step, at least one of the steel pipes is pressed in to a position beyond the faceplate.

5. A connecting widening step that forms a connecting widening section by connecting the first tunnel and the second tunnel which are arranged side by side, A method for constructing an underground structure, comprising a partial widening step of forming a partially widened section by cutting and widening the first tunnel, The aforementioned connecting widening step includes a connecting space construction step that constructs a space in the area between the first tunnel and the second tunnel, A transport route leading to the aforementioned space is provided within the second tunnel. The excavator used in the construction of the second tunnel was left in place. A method for constructing an underground structure, characterized by comprising, after the aforementioned partial widening step, a second partial widening step of removing at least a portion of the lining of the first tunnel adjacent to the excavator and the body of the excavator, and connecting a widening lining to the remaining lining of the first tunnel.

6. A method for constructing an underground structure according to claim 1, 2, or 5, characterized by comprising a boundary construction step of forming a fascia wall of the connected widening section at the boundary between the connected widening section and the partially widened section.

7. A connecting widening step that forms a connecting widening section by connecting the first tunnel and the second tunnel which are arranged side by side, A partial widening process to form a partially widened section by cutting open the first tunnel, A method for constructing an underground structure, comprising a boundary construction step of forming a fascia wall of the connected widening section at the boundary between the connected widening section and the partially widened section, The aforementioned connecting widening step includes a connecting space construction step that constructs a space in the area between the first tunnel and the second tunnel, A transport route leading to the aforementioned space is provided within the second tunnel. The excavator used in the construction of the second tunnel was left at the boundary. A method for constructing an underground structure, characterized in that, in the boundary construction step, a portion of the fascia wall is formed inside the body of the excavator.

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