JP2021059946A - Construction method of underground structure - Google Patents

Abstract

To provide a method for improving the stability of foundation.SOLUTION: A starting base 100 comprises a shell unit 20 disposed along a first wall W1 for supporting the first wall W1, and a side unit 30 disposed along a second wall W2. The side unit 30 has a plurality of pipes 31 fixed to the shell unit 20 for supporting the second wall W2, and a frozen soil layer 32 disposed outside of the pipes 31 for stopping water between the neighboring pipes 31.SELECTED DRAWING: Figure 3

Description

The present invention relates to an underground structure and a method for constructing an underground structure.

In tunnel construction such as road tunnels and railway tunnels, a widened space wider than the main line tunnel may be constructed underground in order to construct a branch / confluence section or a station building section. Patent Document 1 discloses a method of constructing a starting base as a widening space.

In the construction method disclosed in Patent Document 1, first, a cylindrical outer shell portion surrounding the main tunnel and the branch tunnel is constructed. Next, a frozen wall portion is formed so as to close both ends of the cylindrical outer shell portion, and the ground surrounded by the cylindrical outer shell portion and the frozen wall portions at both ends is excavated. A starting base is constructed by constructing a gable wall portion with fiber reinforced concrete or reinforced concrete on the inner wall surface of the frozen wall portion exposed by excavation.

Japanese Unexamined Patent Publication No. 2017-89190

In the construction method disclosed in Patent Document 1, the freezing wall portion is formed by flowing a refrigerant through a freezing pipe inserted into the ground to freeze the ground. Until the gable wall is constructed, the earth pressure along the axial direction of the cylindrical outer shell is applied only to the frozen ground, so there is a risk that the stability of the ground cannot be ensured.

An object of the present invention is to improve the stability of the ground.

The present invention is an underground structure having an underground cavity surrounded by a plurality of wall surfaces of the ground including a first wall surface extending along a predetermined direction and a second wall surface extending from the first wall surface intersecting a predetermined direction. The body includes a shell portion provided along the first wall surface and supporting the first wall surface, and a side portion provided along the second wall surface, and the side portion is fixed to the shell portion and has a first portion. It has a plurality of pipes that support the two wall surfaces, and a ground improvement body that is formed on the outside of the plurality of pipes and stops water between adjacent pipes.

Further, the present invention has an underground cavity surrounded by a plurality of wall surfaces of the ground including a first wall surface extending along a predetermined direction and a second wall surface extending from the first wall surface intersecting a predetermined direction. A method of constructing an underground structure, which is a method of constructing an underground structure, in which a shell portion is provided along the first wall surface to support the first wall surface, a step of providing a side portion along the second wall surface, and a shell. In the process of excavating the area surrounded by the part and the side part to form an underground cavity and providing the side part, a plurality of pipes are inserted into the ground and fixed to the shell part to form a second wall surface. In addition to supporting, a ground improvement body is formed on the outside of a plurality of pipes to stop water between adjacent pipes.

According to the present invention, the stability of the ground can be improved.

It is sectional drawing which shows typically the underground structure which concerns on embodiment of this invention, and the widening space constructed by using the underground structure. It is sectional drawing of the underground structure which concerns on embodiment of this invention, and is sectional drawing along line II-II shown in FIG. It is sectional drawing of the underground structure which concerns on embodiment of this invention, and is sectional drawing along the line III-III shown in FIG. FIG. 5 is an enlarged cross-sectional view of an underground structure according to an embodiment of the present invention, and is a cross-sectional view taken along line IV-IV shown in FIG. It is a figure for demonstrating the construction method of the underground structure which concerns on embodiment of this invention. It is an enlarged sectional view of the underground structure which concerns on the modification of embodiment of this invention, and is shown corresponding to FIG.

Hereinafter, the underground structure and the construction method thereof according to the embodiment of the present invention will be described with reference to the drawings. Here, a case where the underground structure is the starting base 100 of the shield excavator (not shown) will be described.

As shown in FIG. 1, the starting base 100 is used for constructing a widening space 3 in which a branching / merging portion between the existing main line tunnel 1 and the branch line tunnel 2 is formed.

In the following, the direction along the central axis of the main tunnel 1 is referred to as the "tunnel axis direction", and the radial direction centered on the central axis of the main tunnel 1 is referred to as the "tunnel radial direction" around the central axis of the main tunnel 1. The direction of is referred to as the "tunnel circumferential direction".

In order to construct the widened space 3, first, the starting base 100 is constructed in the ground. Next, a shield excavator (not shown) is started from the starting base 100 along the tunnel axial direction, and a plurality of small cross-section shield tunnels 4 are constructed around the main tunnel 1 and the branch tunnel 2. Next, a gable wall 5 is constructed near the arrival point of the shield excavator in the small cross-section shield tunnel 4. The widening space 3 is constructed by excavating the area surrounded by the starting base 100, the plurality of small cross-section shield tunnels 4, and the gable wall 5.

The starting base 100 has an underground cavity 10, and a shield excavator for constructing a small cross-section shield tunnel 4 is installed in the underground cavity 10. Hereinafter, the structure of the starting base 100 and the method of constructing the starting base 100 will be described in detail.

First, the structure of the starting base 100 will be described with reference to FIGS. 2 to 4. It should be noted that FIGS. 2 to 4 show a state before the widening space 3 and the small cross-section shield tunnel 4 shown in FIG. 1 are constructed.

As shown in FIGS. 2 and 3, the underground cavity 10 is surrounded by the first wall surface W1 and the second wall surface W2 of the ground. The first wall surface W1 extends along the tunnel axial direction and is formed in a substantially circular shape so as to surround the main tunnel 1 and the branch tunnel 2. The second wall surface W2 extends from the first wall surface W1 in the radial direction of the tunnel.

The starting base 100 includes a shell portion 20 provided along the first wall surface W1 and a side portion 30 provided along the second wall surface W2. The shell portion 20 and the side portion 30 are constructed in the ground prior to the formation of the underground cavity 10. Inside the side portion 30, a gable wall 36 made of fiber reinforced concrete or reinforced concrete is constructed. In FIG. 2, the gable wall 36 is not shown.

The shell portion 20 is formed in an annular shape. Specifically, the shell portion 20 is formed of a plurality of segments 21 arranged in the tunnel axial direction and arranged in the tunnel circumferential direction so as to surround the main tunnel 1 and the branch tunnel 2.

The segment 21 is, for example, an RC segment mainly formed of concrete, a steel segment mainly formed of steel, or a synthetic segment mainly formed of concrete and steel. The segments 21 adjacent to each other in the circumferential direction of the tunnel are connected to each other and are a hollow structure. The first wall surface W1 of the ground is supported by the plurality of segments 21.

The side portion 30 has a plurality of pipes 31 extending along the second wall surface W2, and a frozen soil layer (ground improvement body) 32 formed on the outside of the plurality of pipes 31. The pipe 31 is, for example, a steel pipe, and is preferably a hollow pipe. The permafrost layer 32 is formed by freezing the ground.

One end of the pipe 31 is connected and fixed through a through hole (not shown) formed in the shell 20. The other end of the pipe 31 is connected and fixed via a through hole (not shown) formed in the shell portion 20, the main line tunnel 1 or the branch line tunnel 2. The second wall surface W2 of the ground is supported by the pipe 31. Therefore, the pressure of the ground in the tunnel axial direction acts on the pipe 31, and the second wall surface W2 of the ground is received by the pipe 31. Therefore, the stability of the ground can be improved.

The pipes 31 are provided substantially parallel to each other. Therefore, the distance between the adjacent pipes 31 is substantially constant over the entire length of the pipes 31. Therefore, the pressure of the ground can be received substantially evenly over the entire length of the pipe 31, and the stability of the ground can be further improved.

The pipe 31 is provided so as to extend in the vertical direction, for example. The pipe 31 may be provided so as to extend in the horizontal direction, or may be provided so as to extend so as to be inclined with respect to the horizontal direction.

FIG. 4 is a cross-sectional view taken along the line IV-IV shown in FIG. In FIG. 4, the gable wall 36 is not shown.

As shown in FIG. 4, the cross section of the pipe 31 is substantially circular. The pipes 31 are provided at intervals from each other. A frozen soil layer 32 is formed between the adjacent pipes 31, and the frozen soil layer 32 stops water between the adjacent pipes 31. Therefore, the inflow of groundwater between the adjacent pipes 31 is blocked. Therefore, it is possible to prevent the groundwater in the ground from flowing into the underground cavity 10 through the space between the pipes 31, and the water is stopped.

An iron plate 33 is provided between the adjacent pipes 31, and the frozen soil layer 32 is covered with the iron plate 33. Therefore, it is possible to prevent the frozen soil layer 32 from collapsing between adjacent pipes 31, and it is possible to improve the water stopping property of the frozen soil layer 32.

Inside the pipe 31, freezing pipes 34 and 35 are arranged along the central axis of the pipe 31. The freezing tubes 34 and 35 are formed so that the refrigerant can flow. The refrigerant is, for example, liquefied carbon dioxide. By flowing the refrigerant through the freezing pipes 34 and 35, the outside of the pipe 31 is cooled, the ground is frozen, and the frozen soil layer 32 is formed.

The second wall surface W2 is a boundary between the ground and the pipe 31 or the frozen soil layer 32. That is, the position of the second wall surface W2 changes depending on the change in the thickness of the frozen soil layer 32. Further, since the frozen soil layer 32 is deformed depending on the frozen state, the position of the second wall surface W2 also changes. For example, in a state where the refrigerant does not flow into the freezing pipes 34 and 35 and the frozen soil layer 32 is not formed, the second wall surface W2 becomes a boundary between the ground and the pipe 31.

Since the freezing pipes 34 and 35 are arranged inside the pipe 31, the freezing pipes 34 and 35 are protected by the pipe 31. Therefore, the breakage of the freezing pipes 34 and 35 can be reduced, and the frozen soil layer 32 can be formed more reliably.

The strength of the pipe 31 is preferably higher than the strength of the freezing tubes 34 and 35. In this case, the freezing pipes 34 and 35 are supported by the pipe 31. Therefore, the breakage of the freezing pipes 34 and 35 can be further reduced, and the frozen soil layer 32 can be formed more reliably. Further, since the outer diameter of the pipe 31 is larger than the outer diameter of the freezing pipes 34 and 35, the cross-sectional performance (for example, the moment of inertia of area) is excellent in terms of strength. Therefore, the pressure of the ground can be received with higher strength than the freezing pipes 34 and 35.

The freezing pipe 34 is arranged on the ground side (opposite to the underground cavity 10) with respect to the central axis of the pipe 31. Therefore, the refrigerant flowing through the freezing pipe 34 cools the region on the ground side of the outside of the pipe 31 with respect to the central axis of the pipe 31 more than the region on the underground cavity 10 side. Therefore, the frozen soil layer 32 can be easily expanded to the ground side, and the water stopping property of the frozen soil layer 32 can be improved.

The freezing pipe 35 is provided at a position closest to the outer peripheral surface of the adjacent pipe 31. That is, the distance between the freezing pipe 35 and the outer peripheral surface of the adjacent pipe 31 is the smallest as compared with other parts. Therefore, the frozen soil layer 32 can be easily formed between the adjacent pipes 31, and the water stopping property of the frozen soil layer 32 can be further improved.

In the example shown in FIG. 4, the freezing pipe 35 is arranged only on one side of the plurality of pipes 31 in the arrangement direction with respect to the central axis of the pipe 31, but may be arranged on both sides in the arrangement direction. In this case, the ground between the adjacent pipes 31 can be cooled by the refrigerant flowing through the freezing pipes 35 provided in each pipe 31. Therefore, the frozen soil layer 32 can be more easily formed between the adjacent pipes 31, and the water stopping property of the frozen soil layer 32 can be further improved.

The freezing tubes 34 and 35 are made of, for example, an aluminum material, and have an IC channel structure (narrow flow path structure) having a plurality of flow paths. Therefore, heat transfer occurs between the refrigerant flowing through the flow paths of the freezing pipes 34 and 35 and the surroundings of the freezing pipes 34 and 35. Therefore, the heat transfer performance of the freezing tubes 34 and 35 can be improved, and the frozen soil layer 32 can be efficiently formed.

Although not shown, the inside of the pipe 31 is filled with a cement-based material such as concrete. Therefore, the strength of the side portion 30 can be increased as compared with the case where the pipe 31 is hollow. Therefore, the stability of the ground can be further improved.

Next, a method of constructing the starting base 100 will be described with reference to FIG.

First, as shown in FIGS. 5 (a) and 5 (b), the ground is excavated from the existing branch line tunnel 2 in the tunnel radial direction to construct a pit 50 which is a widened underground space. The pit 50 can be constructed by a known method, and details of the pit 50 construction method will be omitted.

The pit 50 is constructed, for example, by excavating the ground substantially horizontally from the branch line tunnel 2. The ground may be excavated substantially vertically from the branch line tunnel 2 to construct the pit 50, or the ground may be excavated diagonally from the branch line tunnel 2 in the horizontal direction to construct the pit 50. Further, the pit 50 may be constructed by excavating the ground from the main tunnel 1 in the radial direction of the tunnel.

Next, as shown in FIGS. 5 (c) and 5 (d), the shell portion 20 is formed in the ground so as to surround the main tunnel 1 and the branch tunnel 2. The shell portion 20 can be constructed by a shield method or a propulsion method of digging in the so-called circumferential direction. Specifically, a rectangular shield excavator (not shown) is installed in the pit 50, and the rectangular shield excavator is started from the pit 50. An annular shield tunnel 22 is constructed by advancing the rectangular shield excavator along a circular path so as to surround the main tunnel 1 and the branch tunnel 2. In the example shown in FIG. 5D, three annular shield tunnels 22 are constructed, but the number of annular shield tunnels 22 may be one, two, or four or more.

The first wall surface W1 is formed as the ground is excavated by the rectangular shield excavator. Further, by installing the segment 21 on the first wall surface W1 in accordance with the advance of the rectangular shield excavator, the shell portion 20 is formed, and the first wall surface W1 is supported by the shell portion 20.

Next, as shown in FIGS. 5 (e) and 5 (f), a side portion 30 is formed in the ground. Specifically, a plurality of pipes 31 are inserted into the ground from the inside of the shield tunnel 22 so as to intersect the tunnel axial direction, and a second wall surface W2 is formed on the ground. At this time, the pipe 31 is inserted into the ground while arranging the freezing pipes 34 and 35 (see FIG. 4) inside the pipe 31. The insertion of the pipe 31 is possible by a known method. For example, the pipe 31 can be inserted into the ground by a boring method or a propulsion method. The second wall surface W2 is supported by fixing one end of the pipe 31 to the shell portion 20 and the other end to the shell portion 20, the main line tunnel 1 or the branch line tunnel 2. Next, a refrigerant is passed through the freezing pipes 34 and 35 to freeze the ground on the outer periphery of the pipe 31 to form the frozen soil layer 32.

Next, the area surrounded by the shell portion 20 and the side portion 30 is excavated to form the underground cavity 10 shown in FIGS. 2 and 3. Since the pipe 31 supports the second wall surface W2 of the ground, the pressure of the ground in the tunnel axial direction acts on the pipe 31, and the second wall surface W2 of the ground is received by the pipe 31. Therefore, the collapse of the second wall surface W2 can be prevented, and the underground cavity 10 can be easily formed.

Along with the excavation of the ground, an iron plate 33 (see FIG. 4) is installed between adjacent pipes 31, and a gable wall 36 (see FIG. 3) is constructed. The iron plate 33 and the gable wall 36 are constructed by, for example, a reverse winding method. In the reverse winding method, the iron plate 33 is installed between the adjacent pipes 31 and the gable wall 36 is constructed while forming the underground cavity 10 by excavation from above.

With the above, the construction of the starting base 100 is completed. After the construction of the gable wall 36, the flow of the refrigerant to the freezing pipes 34 and 35 (see FIG. 4) is stopped, and the frozen soil layer 32 is thawed. That is, after the gable wall 36 is constructed, the water is stopped by the skeleton.

According to the above embodiment, the following effects are exhibited.

At the starting base 100, a plurality of pipes 31 support the second wall surface W2. Therefore, the second wall surface W2 of the ground is received by the pipe 31. Therefore, the stability of the ground can be improved. Further, the frozen soil layer 32 stops water between adjacent pipes 31. Therefore, the inflow of groundwater between the adjacent pipes 31 is blocked. Therefore, it is possible to prevent the groundwater in the ground from flowing into the underground cavity 10 through the space between the pipes 31.

Further, the plurality of pipes 31 are provided substantially parallel to each other. Therefore, the distance between the adjacent pipes 31 is substantially constant over the entire length of the pipes 31. Therefore, the pressure of the ground can be received substantially evenly over the entire length of the pipe 31, and the stability of the ground can be further improved.

Further, the side portion 30 is arranged inside the pipe 31, and further includes freezing pipes 34 and 35 through which a refrigerant that freezes the ground can flow. Therefore, the freezing pipes 34 and 35 are protected by the pipe 31. Therefore, the breakage of the freezing pipes 34 and 35 can be reduced, and the frozen soil layer 32 can be formed more reliably.

Further, in the method of constructing the starting base 100, in the step of providing the side portions 30, a plurality of pipes 31 are inserted into the ground and fixed to the shell portion 20 to support the second wall surface W2 and on the outside of the plurality of pipes 31. A frozen soil layer 32 is formed to stop water between adjacent pipes 31. Therefore, in the step of excavating the area surrounded by the shell portion 20 and the side portion 30 to form the underground cavity 10, the second wall surface W2 of the ground is supported and received by the pipe 31. Therefore, the collapse of the second wall surface W2 can be prevented, and the underground cavity 10 can be easily formed.

Although the embodiments of the present invention have been described above, the above embodiments are only a part of the application examples of the present invention, and the technical scope of the present invention is limited to the specific configurations of the above embodiments. Absent.

In the above embodiment, the starting base 100 is used for constructing a branching / merging portion between the existing main line tunnel 1 and the branch line tunnel 2, but the underground structure according to the present invention may be used for another purpose. .. For example, it may be used for constructing a station building such as a railway tunnel. Further, neither the main tunnel 1 nor the branch tunnel 2 may be formed. That is, the present invention can be applied to an underground structure having an underground cavity 10 surrounded by a first wall surface W1 extending along a predetermined direction and a second wall surface W2 extending intersecting the predetermined direction. is there.

In the above embodiment, the side portions 30 are provided on both sides in the tunnel axial direction, but in the present invention, the side portions 30 are provided on one side in the tunnel axial direction, which is different from the side portions 30 on the other side. A structure may be provided.

In the above embodiment, the first wall surface W1 is formed in a substantially circular shape and the shell portion 20 is formed in an annular shape, but the present invention is not limited to this embodiment. For example, the first wall surface W1 may be formed in an arch shape above the underground cavity 10, and the shell portion 20 may be formed in an arch shape along the first wall surface W1. Further, the first wall surface W1 may be formed in an arch shape on the side of the underground cavity 10, and the shell portion 20 may be formed in an arch shape along the first wall surface W1. Further, the first wall surface W1 may be formed in a plane shape, and the shell portion 20 may be formed in a plane shape along the first plane surface. That is, the underground cavity 10 is surrounded by a plurality of wall surfaces of the ground including the first wall surface W1 and the second wall surface W2, and the shell portion 20 and the side portion 30 are along the first wall surface W1 and the second wall surface W2, respectively. It suffices if it is provided.

In the above embodiment, the frozen soil layer 32 stops water between adjacent pipes 31, but the present invention is not limited to this embodiment. For example, a chemical solution may be injected into the ground between adjacent pipes 31 to form a ground improvement body, and water may be stopped between the adjacent pipes 31.

In the above embodiment, the pipes 31 are provided at intervals from each other, but the pipes 31 may be adjacent to each other. Further, as in the modified example shown in FIG. 6, a plurality of pipes may be provided so as to overlap each other in the tunnel axial direction.

In the side portion 30 according to the modified example shown in FIG. 6, the first pipe 131 and the second pipe 231 are alternately arranged, and the space between the first pipe 131 and the second pipe 231 is stopped by the frozen soil layer 32. Has been done. The first pipe 131 has a steel core material 131a and a machinable portion 131b having a hardness lower than that of the core material 131a. The second pipe 231 is a steel pipe like the pipe 31 (see FIG. 4). After inserting the first pipe 131 into the ground, the second pipe 231 is inserted into the ground in parallel with the first pipe 131 while cutting the machinable portion 131b of the first pipe 131. Therefore, the second pipe 231 is arranged in the space formed by cutting the machinable portion 131b. Therefore, the water stopping range between the first pipe 131 and the second pipe 231 can be minimized, and the water stopping of the side portion 30 can be improved. In addition, the strength of the side portion 30 can be improved.

In the modified example shown in FIG. 6, the freezing pipe 34 is arranged on the ground side (opposite to the underground cavity 10) with respect to the central axes of the first pipe 131 and the second pipe 231. The freezing pipe 35 is arranged on an extension of the boundary between the machinable portion 131b and the frozen soil layer 32 inside the second pipe 231. Therefore, the region adjacent to the machinable portion 131b can be efficiently cooled, and water can be easily stopped between the machinable portion 131b and the second pipe 231.

100 ... Starting base (underground structure)
10 ... Underground cavity 20 ... Shell 30 ... Side 31 ... Pipe 32 ... Frozen soil layer (ground improvement body)
34, 35 ... Freezing pipe 131 ... First pipe 231 ... Second pipe W1 ... First wall surface W2 ... Second wall surface

The present invention includes a first wall that Do geotechnical extending along a predetermined direction, and a second wall that Do from the ground extends intersecting the predetermined direction from the first wall, the thus underground cavity surrounded a method for constructing an underground structure to build underground structure having the steps of supporting a first wall surface only set a shell portion formed of concrete along the first wall surface, along a second wall surface a step of providing the side, forming a subsurface cavity drilled region surrounded by the first wall and the second wall comprises a, in the step of providing the side, and a plurality of pipes a predetermined direction It is inserted into the ground so as to extend so as to intersect and fixed to the shell to support the second wall surface, and the refrigerant is placed in the first freezing pipe arranged along the central axis of the pipe on the second wall surface side of the inside of the pipe. Is circulated to form a frozen soil layer on the outside of a plurality of pipes to stop water between adjacent pipes.

Claims (4)

An underground structure having an underground cavity surrounded by a plurality of walls of the ground including a first wall surface extending along a predetermined direction and a second wall surface extending from the first wall surface intersecting the predetermined direction. There,
A shell portion provided along the first wall surface and supporting the first wall surface, and
A side portion provided along the second wall surface is provided.
The side part
A plurality of pipes fixed to the shell portion and supporting the second wall surface,
It has a ground improvement body formed on the outside of the plurality of pipes and stopping water between the adjacent pipes.
Underground structure. The plurality of pipes are provided substantially parallel to each other.
The underground structure according to claim 1. The ground improvement body is a permafrost layer formed by freezing the ground.
The side portion is arranged inside the pipe and further has a freezing pipe through which a refrigerant that freezes the ground can flow.
The underground structure according to claim 1 or 2. An underground structure having an underground cavity surrounded by a plurality of wall surfaces of the ground including a first wall surface extending along a predetermined direction and a second wall surface extending from the first wall surface intersecting the predetermined direction. It is a method of constructing an underground structure to be constructed.
A step of providing a shell portion along the first wall surface to support the first wall surface, and
A step of providing a side portion along the second wall surface and
A step of excavating a region surrounded by the shell portion and the side portion to form the underground cavity is provided.
In the step of providing the side portions, a plurality of pipes are inserted into the ground and fixed to the shell portion to support the second wall surface, and a ground improvement body is formed on the outside of the plurality of pipes to be adjacent to each other. Stop the water between the pipes,
How to build an underground structure.

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