Support structure and method for constructing the support structure

Abstract

We propose a support structure that is less likely to interfere with subsequent excavation processes and a method for constructing this support structure. [Solution] A support structure 3 includes support members installed inside a tunnel and a frozen soil portion 36 formed by freezing ground material filled in the tunnel. The support structure 3 is constructed by fixing one end of the support members to a lining 15 inside the tunnel, laying ground material in at least a part of the tunnel's interior, supporting the other end of the support members on the ground material, and then freezing the ground material.

Description

[Technical Field]

[0001] The present invention relates to a support structure in a tunnel and a method for constructing the support structure. [Background technology]

[0002] At the junctions of road tunnels and at the station areas of railway tunnels, widened sections that are wider than normal main line tunnels may be formed. When widening or connecting existing tunnels, measures must be taken to suppress deformation of the existing tunnel. For example, Patent Document 1 describes the installation of support members such as pillars and beams inside the existing tunnel. Another known method for suppressing deformation of an existing tunnel is to suppress deformation by backfilling part of the tunnel interior with concrete, liquefied treated soil, air mortar, or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 05-332078 Summary of the Invention [Problem to be solved by the invention]

[0004] When installing shoring inside a tunnel, it is common to fix the shoring to the tunnel using steel frames and filler concrete. However, if a portion of the tunnel is excavated later (to connect a new tunnel, etc.), the fixed structure of the shoring will interfere with the excavation work. Furthermore, backfilling the tunnel with concrete will also interfere with the excavation work later. If the tunnel interior is backfilled with liquefied treated soil or air mortar, the backfilled portion can be excavated later, but in low-temperature environments where the surrounding ground is frozen, the strength development of liquefied treated soil and air mortar is delayed, which hinders the shortening of the construction period. An object of the present invention is to propose a support structure that improves the workability of subsequent processes and a method for constructing this support structure. [Means for solving the problem]

[0005] The support structure of the present invention, which solves the above problem, comprises a support member installed in a tunnel and a frozen soil portion formed by freezing ground material filled in the tunnel, one end of the support member being fixed to the tunnel lining and the other end of the support member being fixed to the frozen soil portion.

[0006] In addition, the first support structure construction method of the present invention includes a support member placement process in which one end of a support member is fixed to a lining inside a tunnel, ground material is laid in at least a part of the interior space of the tunnel, and the other end of the support member is supported by the ground material, and a freezing process in which the ground material is frozen.

[0007] Furthermore, the second support structure construction method of the present invention comprises a first freezing step of freezing the ground surrounding the tunnel, a support member placement step of arranging support members with one end fixed to the tunnel lining inside the tunnel, a lining removal step of removing a portion of the tunnel lining to form an opening, a backfilling step of laying ground material in at least a portion of the opening and at least a portion of the interior of the tunnel and supporting the other end of the support member on the ground material, and a second freezing step of freezing the ground material.

[0008] This support structure and construction method allows the reaction force of the support to be transmitted to the ground using frozen soil with high rigidity and strength. In addition, by thawing the ground material, it becomes ground equivalent to the ground, so it does not interfere with subsequent processes.

[0009] The frozen soil portion may be in contact with the surrounding ground of the tunnel through an opening formed in the tunnel. The surrounding ground may be frozen soil. As an example, the support member preferably includes a base portion buried in the frozen soil portion and a shaft portion fixed to the base portion. [Effects of the Invention]

[0010] According to the support structure and the method for constructing the support structure of the present invention, it is possible to improve the workability of subsequent processes. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a cross-sectional view showing the tunnel widening portion of the present embodiment. [Figure 2] FIG. 2 is a longitudinal cross-sectional view showing a part of the tunnel widening section. [Figure 3] FIG. [Figure 4] 1 is a flowchart showing the steps of a method for constructing a support structure. [Figure 5] 10 is a cross-sectional view showing a first freezing step and a support member placement step. FIG. [Figure 6] FIG. 10 is a cross-sectional view showing the lining removal process. [Figure 7] FIG. 10 is a cross-sectional view showing a backfilling step and a second freezing step. [Figure 8] This is a cross-sectional view showing the ramp tunnel after the lining has been removed. [Figure 9] A cross-sectional view showing the ramp tunnel after filling underground. DETAILED DESCRIPTION OF THE INVENTION

[0012] This embodiment illustrates the construction of a tunnel widening section. Figures 1 and 2 show a tunnel widening section 1. As shown in Figures 1 and 2, the tunnel widening section 1 of this embodiment is formed by excavating the inside of a cylindrical outer shell 14 formed by multiple small-section tunnels 13, 13, ... arranged side by side to surround an existing tunnel 10. In this embodiment, a ramp tunnel 11 and a main tunnel 12 are formed as the existing tunnels 10. Note that the number of existing tunnels 10 is not limited.

[0013] The small cross-section tunnel 13 is excavated from a starting base 2 formed at the end of the tunnel widening section 1. The starting base 2 has a cylindrical outer shell 21 consisting of multiple annular tunnels 22, 22 that surround the existing tunnel 10, and a wall 23 formed to shield the end face of the cylindrical outer shell 21. The small cross-section tunnel 13 (outer shell 14) is formed by excavating from the starting base 2 through the wall 23 and along the axial direction of the existing tunnel 10.

[0014] As shown in Figure 1, some of the multiple small cross-section tunnels 13 overlap with parts of the ramp tunnel 11. Therefore, it is necessary to remove the lining of the ramp tunnel 11 in the parts that overlap with the small cross-section tunnel 13. In this embodiment, in conjunction with removing part of the lining of the ramp tunnel 11, a support structure 3 (see Figure 3) is constructed to suppress deformation of the ramp tunnel 11. Figure 3 is a cross-sectional view showing the support structure 3.

[0015] As shown in FIG. 3, the support structure 3 includes a diagonal member 33 installed in the ramp tunnel 11 and a frozen soil section 36 formed by freezing backfill material (e.g., saturated sandy soil) disposed in the ramp tunnel 11 (on the lower left side of the tunnel in FIG. 3). One end of the diagonal member 33 is fixed to the lining 15 of the ramp tunnel 11, and the other end of the diagonal member 33 is fixed to the frozen soil section 36. Furthermore, voids formed with the formation of the frozen soil section 36 (the portion of the tunnel lower section other than the frozen soil section 36 in FIG. 3) are filled with a filler material 5 (e.g., air mortar, liquefied soil, etc.). Note that the material constituting the backfill material is not limited as long as it is a material that can be frozen. The material constituting the filler material 5 is also not limited.

[0016] The method for constructing the support structure 3 will be described below. Figure 4 shows the steps of the method for constructing the support structure 3. As shown in Figure 4, the method for constructing the support structure includes a first freezing step S1, a support member placement step S2, a lining removal step S3, a backfilling step S4, and a second freezing step S5. Figures 5 to 9 show the working conditions of the method for constructing the support structure.

[0017] In the first freezing step S1, the ground around the tunnel (surrounding ground) G is frozen, as shown in Fig. 5. In the first freezing step S1, the surrounding ground G is frozen using a freezing pipe 4 inserted from the starting base 2 into the surrounding ground G of the ramp tunnel 11, forming frozen soil G1 around the ramp tunnel 11. The frozen soil G1 is formed so as to cover the side of the ramp tunnel 11 (the side on the left in Fig. 5) where the ramp tunnel 11 and the small cross-section tunnel 13 overlap.

[0018] In the support member placement process S2, support members are placed inside the tunnel of the ramp tunnel 11. In this embodiment, the support members include vertical members 31 (pillars), horizontal members 32 (beams), and diagonal members 33. Each support member consists of a steel shaft 34 and bases 35 fixed to both ends of the shaft 34. Both ends of the vertical members 31 and horizontal members 32 are fixed to the inner surface of the ramp tunnel 11 lining 15 via the bases 35. The vertical members 31 and horizontal members 32 are positioned so as to ensure reaction force from the frozen soil G1. In this embodiment, the horizontal members 32 are positioned at the center and upper part of the tunnel height, and the vertical members 31 are positioned at the center of the tunnel width and on the side facing the frozen soil G1. The diagonal members 33 extend obliquely from the shoulder of the ramp tunnel 11 away from the frozen soil G1 (upper right side in FIG. 5), through near the center of the ramp tunnel 11, and toward the frozen soil G1 (lower left side in FIG. 5). One end of the diagonal member 33 is fixed to the lining 15 via a base portion 35, and the other end of the diagonal member 33 is positioned at a distance from the lining 15 so as not to come into contact with the small-section tunnel 13 to be constructed in a subsequent process.

[0019] In the lining removal process S3, as shown in Fig. 6, a portion of the lining 15 of the ramp tunnel 11 is removed to form an opening 16. The lining 15 is removed while the surrounding ground G is frozen to prevent soil and groundwater from flowing into the tunnel. The range of the lining 15 to be removed is not limited, but in this embodiment, the range below the lower cross member 32 is removed.

[0020] In the backfilling step S4, as shown in FIG. 7, a portion (lower portion) of the tunnel interior of the ramp tunnel 11 and a portion of the opening are backfilled. In this embodiment, backfilling is performed up to the height of the upper end of the opening 16. At this time, the base portion 35 of the other end (lower end in this embodiment) of the diagonal member 33 is buried in the backfill material (ground material). In this embodiment, the area around the other end of the diagonal member 33 at the bottom of the tunnel is backfilled with ground material (e.g., saturated sandy soil), and the remaining portion is backfilled with filler material 5 (e.g., air mortar, liquefied soil, etc.). Note that freezing pipes 4 are installed around the diagonal member 33.

[0021] In the second freezing step S5, the ground material is frozen to form a frozen soil portion 36. In this embodiment, the ground material around the opening 16 and the other end (base portion 35) of the diagonal member 33 is frozen. This forms a support structure 3 including the diagonal member 33 (support member) installed in the ramp tunnel 11 and a frozen soil portion 36 formed by freezing the ground material filled in the ramp tunnel 11. The frozen soil portion 36 abuts against the surrounding ground G (frozen soil G1) of the ramp tunnel 11 through the opening 16. As a result, one end (upper end) of the diagonal member 33, the other end (lower end) of which is fixed to the remaining lining 15, is supported by the frozen soil portion 36. After the frozen soil portion 36 is frozen, the lower horizontal member 32 is removed.

[0022] Thereafter, the lining removal step S3, backfilling step S4, and second freezing step S5 are repeated to remove a predetermined area of ​​the lining 15, backfill the ramp tunnel 11, and remove unnecessary support members (cross members 32), as shown in Figure 8. At this time, leveling concrete 37 is poured on top of the filler material 5. Once the removal of the predetermined area of ​​the lining 15 is complete, the ramp tunnel 11 is filled with filler material 5, the frozen soil portion 36 is unfrozen, and the frozen pipes 4 inside the ramp tunnel 11 are removed, as shown in Figure 9.

[0023] According to the support structure 3 of this embodiment, the highly rigid and strong frozen soil G1 (frozen soil portion 36) can transmit the support reaction force to the natural ground G. Therefore, even if a part of the lining 15 of the tunnel (ramp tunnel 11) is removed, deformation of the tunnel can be suppressed. Furthermore, the frozen soil portion 36 becomes a ground equivalent to the natural ground G when it is unfrozen, so it does not hinder the excavation of the subsequent process (small cross-section tunnel 13) (see FIG. 9). A base portion 35 is formed in the portion buried in the frozen soil portion 36, and a support member (diagonal member 33) is fixed to this base portion 35, thereby improving the fixation of the support member 33 to the frozen soil portion 36.

[0024] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-described components can be appropriately modified within the scope of the invention. For example, the underground structure that can be constructed using the support structure 3 is not limited. The work in the post-process is not limited to the construction of the small cross-section tunnel 13, but may also be, for example, widening (expanding the diameter) of the tunnel.

[0025] The first freezing step S1 and the lining removal step S3 may be performed as needed. In addition, in the supporting member placement step S2, the soil material may be backfilled and the other end of the diagonal member 33 may be fixed. The arrangement of each support member may be determined as appropriate. [Explanation of symbols]

[0026] 1 Tunnel widening section 10 Existing tunnels 11 Ramp Tunnel 12 Main Line Tunnel 13 Small cross-section tunnel 14 Outer Shell 15 Lining 16 Opening 2 Launch base 21 Cylindrical outer shell 22 Circular Tunnel 23 Wall 3 Support structure 31 Vertical members 32 Cross member 33 Diagonal member (support member) 34 Shaft 35 Base 36 Frozen soil area 4 Cryotube 5 Filling material G Surrounding ground (ground) G1 Frozen soil S1 First freezing step S2 Support member placement process S3 Lining removal process S4 Backfilling process S5 Second freezing process

Claims

1. a support member installed in the tunnel; A support structure comprising: a frozen soil portion formed by freezing the ground material filled in the tunnel; A support structure characterized in that one end of the support member is fixed to the tunnel lining and the other end of the support member is fixed to the frozen ground.

2. 2. The support structure according to claim 1, wherein the frozen soil portion abuts against the surrounding ground of the tunnel through an opening formed in the tunnel.

3. 3. The support structure according to claim 2, wherein the surrounding ground is frozen soil.

4. The support structure according to claim 1 , wherein the support member comprises a base portion buried in the frozen soil portion and a shaft portion fixed to the base portion.

5. a support member placement process for fixing one end of a support member to a lining inside the tunnel, laying a ground material in at least a part of the interior space of the tunnel, and supporting the other end of the support member on the ground material; A method for constructing a support structure, comprising a freezing step of freezing the ground material.

6. a first freezing step for freezing the ground surrounding the tunnel; a support member placement process for placing a support member inside the tunnel, the support member having one end fixed to the lining of the tunnel; a lining removal process of removing a portion of the lining of the tunnel to form an opening; a backfilling step of laying a ground material in at least a part of the opening and at least a part of the interior space of the tunnel and supporting the other end of the support member on the ground material; A method for constructing a support structure, comprising a second freezing step of freezing the ground material.

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