Method for constructing underground structures

Abstract

To provide a method for constructing an underground structure in which a connected widening section and a partial widening section are adjacent to each other, which is less likely to impose restrictions on the work process of each section. [Solution] The construction method comprises a connecting widening process for forming a connecting widening section A by connecting the parallel-arranged first tunnel 1 and second tunnel 2, and a partial widening process for forming a partial widening section C by cutting and widening the first tunnel 1. The connecting widening process includes a first base construction process for forming a first preparation work space S1 outside the first tunnel 1 and the second tunnel 2, which will be used for the construction work of the connecting widening section A. The partial widening process includes a second base construction process for forming a second preparation work space S2 outside the first tunnel 1, which will be used for the construction work of the partial widening section C. In the first base construction process, a loading and unloading route leading to the first preparation work space S1 is provided inside the second tunnel 2, and in the second base construction process, a loading and unloading route leading to the second preparation work space S2 is provided inside the first tunnel 1.

Description

[Technical Field]

[0001] The present invention relates to a method for constructing an underground structure. [Background technology]

[0002] One known method for constructing road junctions underground is to connect two or more parallel tunnels to form a connected widened section, and a partial widened section formed by cutting and widening a single tunnel, in the longitudinal direction of the tunnel (Patent Document 1).

[0003] When constructing connected widening sections and partial widening sections, excavation work is carried out outside the tunnel, and auxiliary construction methods such as shoring, pipe roofing, ground improvement, and freezing methods are often used in conjunction with the work to prevent the ground from collapsing or subsiding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-36435 Summary of the Invention [Problem to be solved by the invention]

[0005] When work is carried out outside the tunnel, it is necessary to secure a space outside the tunnel that will serve as a construction base (hereinafter referred to as the "preparation work space"), and to carry materials and heavy machinery used for auxiliary construction methods, etc. into the preparation work space through the tunnel, while simultaneously carrying out the removed lining, soil, etc. from the preparation work space into the tunnel. If such work is carried out in both the connected widening section and the partial widening section, there is a risk that delays in the work process in one section will affect 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 partial widening section are adjacent to each other, so that even if a delay occurs in the work process in one section, the other section is less likely to be affected. [Means for solving the problem]

[0007] The present invention is a method for constructing an underground structure, comprising a connecting and widening process for forming a connecting and widening section by connecting a first tunnel and a second tunnel arranged side by side, and a partial widening process for forming a partial widening section by cutting and widening the first tunnel. The connecting and widening process includes a first base construction process of forming at least one first preparation work space outside the first tunnel and the second tunnel, which will serve as a construction base used for construction work on the connecting and widening section. The partial widening process includes a second base construction process of forming at least one second preparation work space outside the first tunnel, which serves as a construction base used for construction work on the partial widening section. Then, in the first base construction process, a loading / unloading route leading to the first preparation work space is established within the second tunnel, and in the second base construction process, a loading / unloading route leading to the second preparation work space is established within the first tunnel.

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

[0009] The connecting and widening step may include a connecting space constructing step of constructing a space in the region between the first tunnel and the second tunnel. The partial widening process may include a pipe roof installation process in which a plurality of steel pipes constituting a pipe roof along the first tunnel are pressed from the second preparation work space into the surrounding ground of the first tunnel; a lining removal process in which a portion of the lining of the first tunnel located below the pipe roof is removed from inside the first tunnel; an widening space construction process in which a space communicating with the opening formed by the lining removal process is constructed outside the first tunnel; and an widening lining construction process in which an widening lining is connected to the remaining lining of the first tunnel. When excavation work of the natural ground is performed in the connecting and widening process, the excavated earth can be transported out via the second tunnel. When pipe roof installation work is performed in the partial widening process, materials and equipment necessary for the pipe roof installation work can be transported in via the first tunnel, and when excavation work of the natural ground or lining removal work is performed, excavated earth, etc. can be transported out via the first tunnel. In other words, according to one preferred embodiment of the present invention, the connecting space construction process can be performed in the connecting and 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] In the first base construction step, it is preferable to form an adit as the first preparation work space on the partial widening section side of a boundary between the connecting widening section and the partial widening section. In this case, it is preferable to start excavation work from the adit in the connecting space construction step, and alternately perform work of excavating the natural ground and work of installing shoring. In this way, the cross tunnel can also be used for construction work near the boundary between the connecting widening section and the partial widening section, thereby shortening the construction period.

[0011] If the barrel of the excavator used in the construction of the second tunnel is left in place, it is preferable that the opening provided in the barrel be used to form the cross tunnel in the first base construction process. Typically, the barrel of the excavator is made of steel, so that an opening can be easily formed by gas cutting or the like.

[0012] In the pipe roof installation step, it is preferable to press-fit at least one of the steel pipes into the adit. In this way, even when the widening space construction process is carried out in a partial widening section close to the cross-section, ground deformation caused by excavation can be suppressed.

[0013] In addition, when a second preparation work space is set up near the boundary between the connected widening section and the partial widening section in the second base construction process, it is preferable to carry out the second base construction process (work to construct the second preparation work space) after the second tunnel boring machine reaches the vicinity of the boundary between the connected widening section and the partial widening section, so as not to affect the construction work of the second tunnel or the adit construction work. On the other hand, if, in the second base construction process, the second preparation work space is formed closer to the partial widening section than the cross tunnel, and the steel pipe is pressed from the second preparation work space toward the boundary in the pipe roof installation process, the second base construction process can be carried out before the second tunnel boring machine reaches the vicinity of the boundary between the connecting widening section and the partial widening section, thereby shortening the construction period.

[0014] If the excavator used in the construction of the second tunnel is left in place, it is preferable that in the pipe roof installation process, at least one steel pipe is pressed into the face plate of the excavator. In this way, even when the widening space construction process is carried out in a partial widening section close to the second tunnel boring machine, ground deformation caused by 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 carry out a second partial widening process after the partial widening process in which the lining of the first tunnel adjacent to the excavator and at least a part of the body of the excavator are removed and an widening lining is connected to the remaining lining of the first tunnel. In this way, even if the boring machine for the second tunnel is left in place, the first tunnel can be widened in the area adjacent to that boring machine.

[0016] In the second base construction process, it is preferable that a plurality of the second preparation work spaces are formed at positions offset in the circumferential and longitudinal directions of the first tunnel. In this way, each second preparation work space can be made smaller, thereby reducing the risk of ground deformation. When a plurality of second preparation work spaces are formed, it is preferable to form pilot tunnels that connect the second preparation work spaces to each other. In this way, it is only necessary to connect any one of the multiple second preparation work spaces to the first tunnel (i.e., it is only necessary to provide one opening in the first tunnel), thereby reducing the impact on the strength of the first tunnel.

[0017] A boundary construction step is preferably performed at the boundary between the connecting widening section and the partial widening section. In the boundary construction step, a side wall of the connecting widening section is preferably formed. Forming a flange at the boundary between the connecting widened section and the partial widened section increases the strength of the structurally changed section and also suppresses the occurrence of water leakage. [Effects of the Invention]

[0018] According to the present invention, when constructing an underground structure in which a connected widening section and a partial widening section are adjacent to each other, even if there is a delay in the work process in one section, it is unlikely to affect the other section. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a plan view showing an underground structure according to an embodiment. [Figure 2] (a) is a cross-sectional view of the connecting widening section (cross-sectional view 2A-2A in Figure 1), (b) is a cross-sectional view of the switching section (cross-sectional view 2B-2B in Figure 1), and (c) is a cross-sectional view of the partial widening section (cross-sectional view 2C-2C in Figure 1). [Figure 3] 1 is a flowchart for explaining a method for constructing an underground structure according to an embodiment. [Figure 4] FIG. 10 is a plan view illustrating the connecting and widening step. [Figure 5]4 in the widening process, (b) is a cross-sectional view of FIG. 4 taken along 5B-5B, (c) is a cross-sectional view of FIG. 4 taken along 5C-5C, and (d) is a cross-sectional view of FIG. 4 taken along 5D-5D. [Figure 6] FIG. [Figure 7] 1(a) is a vertical cross-sectional view of a vertical hole which is the first work preparation space, and FIG. 1(b) is a horizontal cross-sectional view. [Figure 8] 1 is a flowchart of the shaft construction process. [Figure 9] (a) is a plan view for explaining the second base construction process for a modified example, (b) is a cross-sectional view of (a) taken along 9B-9B, and (c) is a cross-sectional view of (a) taken along 9C-9C. DETAILED DESCRIPTION OF THE INVENTION

[0020] As an embodiment of the present invention, an underground structure 100 that serves as a branching and merging point of a road is exemplified. As shown in Figure 1, the underground structure 100 comprises a connected widening section A connecting the first tunnel 1 and the second tunnel 2, a partial widening section C formed by cutting and widening the first tunnel 1, and a switching section B provided between the connected widening section A and the partial widening section C.

[0021] The first tunnel 1 is a main tunnel that contains the main road line. The second tunnel 2 is a ramp tunnel that includes a merging lane that merges with the main line or a diverging lane that branches off from the main line, and is installed next to the first tunnel 1. The first tunnel 1 and the second tunnel 2 are shield tunnels (tunnels constructed by the shield method). Note that the first tunnel 1 and the second tunnel 2 may be tunnels constructed by a method other than the shield method (for example, tunnels constructed by the jacking method).

[0022] As shown in Figure 2(a), the connected widening section A is a section with an internal area larger than the combined internal area of ​​the first tunnel 1 and the second tunnel 2. The connected widening section A has a large cross-section lining 101 that connects the first tunnel 1 and the second tunnel 2. The large cross-section lining 101 includes 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 partial widening section C is a section having an internal space area larger than the internal space area of ​​the first tunnel 1 and smaller than the internal space area of ​​the connecting widening section A. The partial widening 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 an expansion lining 14 added to the outside of the first tunnel 1.

[0024] As shown in Figure 2(b), the switching section B is a section (boundary section) 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 switching section B. That is, the underground structure 100 has a boundary section 3 provided between the large cross-section lining 101 and the small cross-section lining 102. The boundary section 3 has a flank wall 33. The flank wall 33 is a wall that closes the opening that occurs due to the difference in cross-sectional shape between the connected widening section A and the partial widening section C.

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

[0026] <1. Tunnel construction process> The tunnel construction process is a process of constructing multiple tunnels. The tunnel construction process of this embodiment includes "1.1 First tunnel construction process" and "1.2 Second tunnel construction process." The first tunnel construction process is a process of constructing a 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 step is a step of constructing a second tunnel 2 for a ramp in at least the connecting and widening section A and the switching section B. In this embodiment, the first tunnel 1 and the second tunnel 2 are constructed using a shield tunneling method. There are no restrictions on the types 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, a first tunnel 1 and a second tunnel 2 are installed side by side with a gap between them. In the second tunnel construction process, the trunk 22 of the excavator used in the construction of the second tunnel 2 is left behind. In this embodiment, the excavator is advanced along the first tunnel 1 until the entire excavator passes beyond the switching section B. Then, after removing the equipment inside the excavator (face plate drive device, erector, propulsion jack, etc.), the trunk 22 is left behind at the side of the first tunnel 1. The first tunnel construction process and the second tunnel construction process may be carried out one before the other, or may be carried out simultaneously.

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

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

[0029] (1) First base construction process As shown in Figures 4, 5(a) and 5(b), the first base construction process is a process of forming at least one first preparation work space S1 outside the first tunnel 1 and the second tunnel 2. The first preparation work space S1 serves as a construction base used for the construction work of the connected widening section A. In the first base construction process, a loading / unloading route leading to the first preparation work space S1 is set up inside the second tunnel 2. In this embodiment, an opening communicating with the first preparation work space S1 is provided in the trunk 22 of the excavator. Since the trunk 22 is usually made of steel, the opening can be easily formed by gas cutting or the like. When materials and equipment are to be brought into the first preparation work space S1, they are brought into the body 22 of the excavator from the entrance of the second tunnel 2 (not shown), and then the materials and equipment are brought into the first preparation work space S1 using a lifting device or a hoisting device (not shown) installed in line with the opening of the body 22. When materials and equipment or excavated waste soil are to be removed from the first preparation work space S1, they are first carried into the body 22 through the opening of the body 22, and then the materials and equipment are carried out to the entrance of the second tunnel 2 (not shown).

[0030] The first preparation work space S1 in this embodiment includes an adit S11 and shafts S12, S12. The adit S11 extends in a direction crossing the first tunnel 1 and the second tunnel 2. The 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 adit S11 is formed closer to the partial widening section C than the switching section B (the boundary between the connecting widening section A and the partial widening 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 adit S11. The adit S11 is supported by steel supports and shotcrete. The process of constructing the adit (adit construction process) includes the work of forming an opening in the body 22 of the excavator, the work of excavating the ground around the body 22 from the opening in the body 22 and forming the entrance part of the adit S11 on the outside of the body 22, and the work of extending the adit S11 to directly above the first tunnel 1 while supporting the ground exposed in the adit S11 with steel supports and shotcrete.

[0032] As shown in Figure 4, the shafts S12, S12 are formed closer to the connecting widening section A than the horizontal shaft S11, and are used as a space (preparation work space) for various work 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 shaft S12, and the outer surface of the second tunnel 2 is exposed in the other shaft S12. The shaft S12 is constructed from the horizontal shaft S11 toward the start end of the connecting widening section A (the end opposite the switching section B). The process of constructing the shaft S12 (shaft construction process) will be described in detail later.

[0033] (2) Connected space construction process The connecting space construction process is a process of constructing a space (connecting space V1) in the region between the first tunnel 1 and the second tunnel 2. The connecting space V1 in this embodiment 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). Thereafter, a process of excavating an area adjacent to the outer surface of the shield tunnel and adjacent to the vertical shaft S12 (main excavation process) and a process of installing shoring (second shoring member 52 in this embodiment) along the top surface of the space formed by the excavation (second shoring process) are carried out alternately. Details of the second shoring process will be described later. In the lower half of the connected widening section A, the process of excavating the ground in the area sandwiched between the first tunnel 1 and the second tunnel 2 and the process of erecting support members between the first tunnel 1 and the second tunnel 2 are carried out alternately.

[0034] (3) First widening lining construction process The first widening lining construction process is a process of connecting arch-shaped connecting linings 12, 13 (see Figure 2(a)) to the lining of the first tunnel 1 and the lining of the second tunnel 2. The connecting linings 12, 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, 13 is connected to the lining of the first tunnel 1, and the other end of the connecting linings 12, 13 is connected to the lining of the second tunnel 2. The connecting linings 12, 13 may be formed by placing a center (not shown) in the connecting space V1 and pouring concrete between the center and the natural ground, or may be formed by assembling segments similar to those for a shield tunnel within the connecting space V1.

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

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

[0037] (1) Second base construction process The second base construction process is a process of forming at least one second preparation work space S2 outside the first tunnel 1, as shown in (d) of FIG. 5. The second preparation work space S2 serves as a construction base used for the construction work of the partial widening section C. The second preparation work space S2 shown in (d) of FIG. 5 is an adit extending in a direction intersecting the first tunnel 1. In the second base construction process, a carry-in / out route leading to the second preparation work space S2 is provided within the first tunnel 1. As shown in FIG. 4, in this embodiment, the second preparation work space S2 is formed closer to the partial widening section C than the adit S11 (closer to the partial widening section C than the switching section B). When the second preparation work space S2 is formed at a position away from the adit S11, the second base construction process can be carried out before the boring machine of the second tunnel 2 reaches the switching section B (near the boundary between the connecting widening section A and the partial widening section C), thereby shortening the construction period.

[0038] (2) Pipe roof installation process The pipe roof installation process is a process of forming a pipe roof 15 above the first tunnel 1. As shown in FIG. 5(c), in the pipe roof installation process, multiple steel pipes that make up the pipe roof 15 are press-fitted into the ground surrounding the first tunnel 1. In the pipe roof installation process of this embodiment, the second preparation work space S2 (see FIG. 5(d)) is used as the construction base for the pipe roof construction method, and steel pipes are press-fitted from the second preparation work space S2 toward the switching section B. As shown in FIG. 4, in this embodiment, at least one steel pipe is press-fitted to a position just before the adit S11, and at least one steel pipe is press-fitted to a position above the body 22 that exceeds the face plate of the excavator. In this way, ground deformation associated with excavation can be suppressed even when the second excavation process is performed in the adit S11 and the partial widening section C close to the excavator.

[0039] It is possible to construct the adit S11 before carrying out the pipe roof installation process, but if there is a risk that the pipe roof 15 will be hit by the steel support of the adit S11 when it arrives, it is better to construct the adit S11 after carrying out the support pipe roof installation process.

[0040] (3)Second lining removal process The second lining removal process is a process of removing a portion of the lining of the first tunnel 1 located below the pipe roof 15 from inside the first tunnel 1. Note that before the second lining removal process, ground improvement or freezing may be performed on the ground surrounding the first tunnel 1.

[0041] (4) Widening space construction process The widening space construction process is a process of constructing a space (widening space V2) outside the first tunnel 1 that is connected to the opening formed by the second lining removal process. In the widening space construction process, the natural ground exposed by the lining removal is excavated from inside the first tunnel 1 toward the outside, and an widening space V2 that is connected to the interior of the first tunnel 1 is formed, as shown in (c) of Figure 2.

[0042] (5) Second widening lining construction process The second widening lining construction process is a process of connecting the widening lining 14 to the remaining lining 11 of the first tunnel 1.

[0043] The second lining removal process, the second excavation process, and the second widening lining construction process may be repeated for 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 process is a process of constructing a partial widening section C in an area adjacent to the excavator body 22. The second partial widening process is preferably carried out after the first partial widening process. In the second partial widening process of this embodiment, the lining of the first tunnel 1 adjacent to the excavator body 22 and at least a part of the excavator body 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 portion construction step is a step of forming the boundary portion 3 in the switching section B. The boundary portion 3 includes an outer shell 31, an inner shell 32, and a side wall 33, as shown in FIG.

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

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

[0048] The hem wall 33 is formed in the area surrounded by the outer shell 31 and the inner shell 32. That is, the hem wall 33 is formed inside the outer shell 31 and outside the inner shell 32. The hem wall 33 of this embodiment includes a concrete section poured 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, vertical ribs of steel segments, etc.) that are anchored to the concrete section. This integrates the outer shell 31 and the concrete section, and also integrates the inner shell 32 and the concrete section, thereby improving the waterproofing properties of the hem wall 33.

[0049] As shown in Figure 6, the hem 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 the tunnel axial reinforcement 33b. The tunnel radial reinforcement 33c is inserted between adjacent longitudinal ribs in the steel segments 43 that make up the outer shell 31. In this way, the hem wall 33 has a steel-concrete composite structure with the steel segments 43 as a steel shell, thereby improving the durability of the boundary 3.

[0050] Although not shown in the figure, the boundary portion 3 is provided with an outer water-stopping member that stops water from flowing between the outer shell 31 and the hem wall 33, and an inner water-stopping member that stops water from flowing between the inner shell 32 and the hem wall 33. The outer water-stopping member is, for example, a water-expandable sealing material, and is adhered to the inner surface of the outer shell 31 (in this embodiment, the inner end surface of the main girder of the steel segment) at the boundary between the switching section B and the partial widening section C. The inner water-stopping member is, for example, a water-swellable sealing material, and is bonded to the outer circumferential 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, an outer bottom formwork is first installed at the boundary between the transition section B and the partial widening section C to close the opening at the end face of the connecting widening section A. An outer waterproofing member is attached to the inner surface of the outer shell 31, and an inner waterproofing member is attached to the outer surface of the inner shell 32. Next, tunnel circumferential reinforcement 33a, tunnel axial reinforcement 33b, and tunnel radial reinforcement 33c are arranged. Next, an inner bottom formwork is installed facing the outer bottom formwork. Concrete is then poured into the space surrounded by the outer shell 31, inner shell 32, outer bottom formwork, and inner bottom formwork. Once the concrete reaches its demolding strength, the inner bottom formwork is demolded. The adit S11 can also be used in the boundary construction process, thereby shortening the construction period.

[0052] <Vertical shaft construction process> The vertical shaft construction process included in "(1) First base construction process" of "2.1 Connection and widening process" shown in Figure 3 will be described in detail.

[0053] As shown in FIG. 7(b), the vertical shaft S12 is an advance pilot tunnel supported by a first support member 41 and shotcrete. The first support member 41 is a steel support and is supported by the lining of the first tunnel 1 or the lining of the second tunnel 2. As shown in FIG. 7(a), the first support member 41 is arranged in accordance with the main girder 43a of the steel segment 43 that constitutes the lining of the first tunnel 1 or the second tunnel 2. In this embodiment, the first support member 41 is arranged at a position where adjacent steel segments 43, 43 in the tunnel axial direction butt against each other, and the lower end of the first support member 41 is fixed to a skin plate 43b by welding. In other words, 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, a support leg 51, a support girder 53, a bracket 54, an intermediate girder 55, a dam plate 56, and a filler 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. The support leg 51 in this embodiment is made of steel (H-beam, I-beam, etc.). The support leg 51 is joined to the support girder 53 between the first support members 41, 41 that are adjacent in the girder direction of the support girder 53.

[0056] The support girder 53 is a girder member extending in a direction intersecting the first support member 41. The lower ends of the support legs 51 are joined to the support girder 53. The support girder 53 is arranged 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. The support girder 53 is preferably abutted against the inner surfaces of at least two first support members 41 arranged side by side 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 supporting the support legs 51 on the support girder 53, even if the support legs 51 cannot be installed in accordance with the main girders 43a of the steel segments 43, the fulcrum of the support legs 51 is stabilized, thereby improving the stability of the second support members 52 supported by the support legs 51 and ultimately suppressing deformation of the surrounding ground of the connection space V1.

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

[0058] The intermediate girder 55 is a girder member extending in a direction intersecting with 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 the brackets 54. It is preferable that the intermediate girder 55 spans at least two brackets 54, 54 arranged side by side in the tunnel axis direction. The intermediate girder 55 in this embodiment is made of steel (H-beam, I-beam, etc.).

[0059] The bracket 54 may be omitted, and the intermediate girder 55 may be fixed directly to the first supporting member 41. Furthermore, when the support leg 51 is arranged to match the position of the main girder 32a of the steel segment 43 (for example, when the support leg 51 is arranged to match the position of the first supporting member 41, or when the support leg 51 is arranged to match the position of the main girder 43a between adjacent first supporting members 41, 41 in the tunnel axis direction (extension direction of the vertical shaft S12)), the support girder 53, the bracket 54, and the intermediate girder 55 may be omitted, and the support leg 51 may be fixed directly to at least one of the first supporting member 41 and the skin plate 43b. In this case, the second supporting member 52 may be joined to the first supporting member 41, and the first supporting member 41 may be interposed between the support leg 51 and the second supporting member 52.

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

[0061] Filler 57 is filled into the interior space of shaft S12 above dam plate 56. Filler 57 is made of concrete, mortar, liquefied treated soil, or the like, which has a strength equal to or greater than that of the surrounding ground. Filling the interior space of shaft S12 above dam plate 56 with filler 57 increases the stability of support leg 51, which in turn increases the stability of second support member 52 supported by support leg 51, thereby increasing the stability of the arch connecting support leg 51 and second support member 52 and making it possible to suppress deformation of the surrounding ground.

[0062] The shaft construction process is a process included in the first base construction process in the connection and widening process (see Figure 3). As shown in Figure 8, the shaft construction process includes an advance excavation process, a first support process, a spraying process, a girder installation process, a support leg installation process, a dam plate installation process, and a filling process.

[0063] The advance excavation process is a process of excavating the ground from the horizontal tunnel S11 above the first tunnel 1 or the second tunnel 2 toward the start of the connected widening section A, as shown in Figures 4 and 5(a), to form a first preparation work space S1 (vertical tunnel S12) adjacent to the first tunnel 1 or the second tunnel 2. The first support step is a step of installing first support members 41 (see FIG. 7) along the natural ground exposed by the advance excavation step. Placing the first support members 41 can suppress deformation occurring on the inner wall surface of the shaft S12 due to soil and water pressure in the surrounding natural ground. In the first support step, as shown in FIG. 7(a), the first support members 41 are placed in alignment with the positions of the main girders 43a (main structures of the segment rings) of the steel segments 43 that make up the shield tunnel. Placing the first support members 41 in alignment with the main girders 43a of the steel segments 43 allows the force acting on the first support members 41 to be transmitted to the main girders 43a of the steel segments 43. Supporting the first support members 41 on the main girders 43a of the steel segments 43 stabilizes the support points of the first support members 41, effectively suppressing deformation occurring on the inner wall surface of the shaft S12.

[0064] The spraying process is a process of spraying concrete onto the natural ground (the inner wall surface of the shaft S12) exposed by the advance 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 more effectively suppressed. The advance excavation process, the first support process, and the spraying process may be repeated for one or several rings of the first tunnel 1 or the second tunnel 2. Alternatively, the advance excavation process and the first support process may be performed alternately, and the spraying process may be performed after forming the vertical shaft S12 over the entire length of the connected widening section A. Alternatively, the advance excavation process may be performed over the entire length of the connected widening section A, and then the first support process and the spraying process may be performed sequentially.

[0065] The girder installation step is a step of placing the support girder 53, the bracket 54 and the intermediate girder 55 at predetermined positions in the shaft S12, as shown in FIG. 7(b).

[0066] The support leg installation process is a process of installing the support leg 51 in the vertical shaft S12. In the support leg installation process of this embodiment, the support leg 51 is placed between the first support members 41, 41 adjacent to each other in the girder 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. If the support leg 51 is supported by the support girder 53 and the intermediate girder 55, the force acting on the support leg 51 is transmitted to the main girder 43a of the steel segment 43 via the first support member 41, resulting in a stable structure.

[0067] The dam plate installation step is a step of installing the dam plate 56 so as to cover at least two support legs 51 arranged side by side in the extension direction of the vertical shaft S12. In the dam plate installation step, the dam plate 56 is installed on the back side of the support legs 51.

[0068] The filling step is a step of filling the space between the first support member 41 and the support leg 51 with the filler material 57. In the filling step of this embodiment, the filler material 57 is filled into the space inside the vertical shaft S12 above the dam plate 56. When the filler 57 has attained a predetermined strength, the process proceeds to "(2) First Excavation Step" of "2.1 Connection and Widening Step" shown in FIG.

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

[0070] The second support process, which is included in the connecting space construction process, is a process of installing second support members 52 along the natural ground exposed by the main excavation process. The second support members 52 are arch-shaped temporary materials that fit along 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 members 52 are made of steel (H-beams, I-beams, etc.). The end faces of the second support members 52 are joined to the upper end faces of the support legs 51 that have been installed in advance. The support legs 51 in the vertical shaft S12 serve as bases for the second support members 52, facilitating the installation work of the second support members 52. Furthermore, the second support members 52 and the support legs 51, 51 installed on both sides thereof form a continuous arch that serves to suppress deformation of the natural ground exposed by the main excavation process. In this way, the second support member 52 is arranged within the connecting space V1 (main working space) formed outside the shield tunnel, thereby suppressing deformation that occurs on the inner wall surface of the connecting space V1 due to soil and water pressure from the surrounding ground. Once the second support process has been 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] <Actions and effects of the method for constructing an underground structure according to the embodiment> As described above, according to the method for constructing an underground structure relating to the embodiment, materials and equipment for constructing the connected widening section A are transported in and out to 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 in and out to the construction base outside the first tunnel 1 via the first tunnel 1, so even if the connected widening section A and the partial widening section C are constructed at the same time, materials and equipment can be transported in and out smoothly.

[0072] In addition, the connecting space construction process can be carried out in the connecting 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, thereby shortening the construction period.

[0073] Furthermore, according to the method for constructing an underground structure of the embodiment, the vertical shaft S12 formed outside the first tunnel 1 and the second tunnel 2 is supported by the first support members 41, which makes it possible to suppress deformation occurring on the inner wall surface of the vertical shaft S12 due to soil and water pressure in the surrounding ground. Moreover, since the first support members 41 are positioned in accordance with the main girders 43a of the steel segments 43 (the main structure of the segment ring), the force acting on the first support members 41 can be transmitted to the first tunnel 1 and the second tunnel 2. If the first support members 41 are supported by the main girders 43a of the steel segments 43, the support points of the first support members 41 are stabilized, which makes it possible to effectively suppress deformation occurring on the inner wall surface of the vertical shaft S12.

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

[0075] <Variation 1> The steps and structures in the above-described embodiment may be modified as appropriate depending on the construction conditions and the like. For example, in the above embodiment, the case where there is one second preparation work space S2 has been exemplified, but as shown in Fig. 9, in the second base construction step, multiple second preparation work spaces S2 may be formed at positions shifted 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 work spaces S2, S2. In this way, the size of each second preparation work space S2 is reduced, so that deformation of the ground and the first tunnel 1 can be suppressed.

[0076] <Variation 2> In the above-described embodiment, the first support member 41 is arranged to match the position of the main girder 43a of the steel segment 43, but the first support member 41 may be arranged at a position offset from the main girder 43a. In this case, it is preferable to arrange the support leg 51 to match the position of the main girder 32a of the steel segment 43, arrange the support girder so as to connect the lower ends of adjacent support legs 51, 51 in the tunnel axis direction, and have the first support member 41 supported by this support girder. When the support leg 51 is arranged to match the position of the main girder 43a of the steel segment 43, the fulcrum of the support leg 51 is stabilized, thereby increasing the stability of the second support member 52 supported by the support leg 51, and suppressing deformation occurring on the inner wall surface of the main working space (connecting space V1) formed by the main excavation process. Furthermore, if a support girder is provided and the first support member 41 is 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 ground surrounding the vertical shaft S12. [Explanation of symbols]

[0077] 100 Underground structures 101 Large section lining 102 Small section lining A Connected widening section B Switching section C Partial widening 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 Lining (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 legs 52 Second Support Member 53 Support girder 54 Bracket 55 Middle girder 56 Weir plate 57 Filling material

Claims

1. a connecting and widening step of forming a connecting and widening section connecting the first tunnel and the second tunnel arranged side by side; A method for constructing an underground structure, comprising: a partial widening step of forming a partial widening section by cutting and widening the first tunnel, The connecting and widening step includes a first base construction step of forming at least one first preparation work space outside the first tunnel and the second tunnel, the first preparation work space serving as a construction base used for construction work of the connecting and widening section, The partial widening step includes a second base construction step of forming at least one second preparation work space outside the first tunnel, which serves as a construction base used for construction work of the partial widening section, In the first base construction step, a carry-in / out route leading to the first preparation work space is provided in the second tunnel, A method for constructing an underground structure, characterized in that in the second base construction process, a loading / unloading route leading to the second preparation work space is established within the first tunnel.

2. The connecting and widening step includes a connecting space construction step of constructing a space in the region between the first tunnel and the second tunnel, 2. The method for constructing an underground structure according to claim 1, characterized in that the partial widening process includes a pipe roof installation process in which a plurality of steel pipes constituting a pipe roof along the first tunnel are pressed from the second preparation work space into the surrounding ground of the first tunnel; a lining removal process in which a portion of the lining of the first tunnel located below the pipe roof is removed from inside the first tunnel; an widening space construction process in which a space communicating with the opening formed by the lining removal process is constructed outside the first tunnel; and an widening lining construction process in which an widening lining is connected to the remaining lining of the first tunnel.

3. In the first base construction step, a side tunnel as the first preparation work space is formed on the partial widening section side of the boundary between the connecting widening section and the partial widening section, A method for constructing an underground structure as described in claim 2, characterized in that in the connecting space construction process, excavation work begins starting from the horizontal tunnel, and work to excavate the ground and work to install supports are carried out alternately.

4. The body of the excavator used in the construction of the second tunnel is left in place, The method for constructing an underground structure according to claim 3, characterized in that in the first base construction step, the adit is formed using an opening provided in the body portion.

5. 5. The method for constructing an underground structure according to claim 4, wherein in the pipe roof installation step, at least one of the steel pipes is press-fitted to a position where it intersects with the adit.

6. In the second base construction step, the second preparation work space is formed on the side of the adit toward the partial widening section, 4. The method for constructing an underground structure according to claim 3, wherein in the pipe roof installation step, the steel pipe is press-fitted from the second preparation work space toward the boundary.

7. In the first base construction step, a side tunnel as the first preparation work space is formed on the partial widening section side of the boundary between the connecting widening section and the partial widening section, 7. The method for constructing an underground structure according to claim 6, wherein in the pipe roof installation step, at least one of the steel pipes is press-fitted to a position where it intersects with the adit.

8. The excavator used in the construction of the second tunnel will be left in place, 7. The method for constructing an underground structure according to claim 6, wherein in the pipe roof installation step, at least one of the steel pipes is press-fitted up to a face plate of the excavator.

9. A method for constructing an underground structure as described in claim 8, characterized in that after the partial widening process, a second partial widening process is provided in which the lining of the first tunnel adjacent to the excavator and at least a part of the body of the excavator are removed, and an widening lining is connected to the remaining lining of the first tunnel.

10. 9. The method for constructing an underground structure according to claim 8, wherein in the pipe roof installation step, at least one of the steel pipes is press-fitted to a position beyond the face plate.

11. A method for constructing an underground structure as described in claim 1, characterized in that in the second base construction process, multiple second preparation work spaces are formed at positions shifted circumferentially and longitudinally of the first tunnel.

12. The method for constructing an underground structure according to claim 11, further comprising forming a pilot tunnel connecting the second preparation work spaces.

13. 2. The method for constructing an underground structure according to claim 1, further comprising a boundary construction step of forming a flank wall of the connecting widening section at the boundary between the connecting widening section and the partial widening section.

14. leaving the excavator used in the construction of the second tunnel at the boundary; 14. The method for constructing an underground structure according to claim 13, wherein in the boundary portion construction step, a part of the side wall is formed inside a body portion of the excavator.

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