JP2016008425A - Construction method for large section tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently construct a large-section tunnel with proper workability in such a manner as to construct a branch junction part, in which two tunnels are joined together, as the large-section tunnel without intermingling with construction of each of the two tunnels.SOLUTION: A plurality of starting adits, which are extended in a horizontal direction orthogonal to an axis line of one tunnel from a side wall part, positioned on the outside of a large-section tunnel construction-planned area, of either of the two tunnels joined together to form a branch junction part, are constructed at intervals in the axial direction of the one tunnel.

Description

  The present invention relates to a construction method of a large cross-section tunnel for constructing a branching junction where two tunnels join as a large cross-section tunnel.

  Conventionally, when constructing a branching junction where two shield tunnels join in a deep underground as a large cross-section tunnel, a reinforcement body that isolates the area where the large cross-section tunnel is planned from the outside ground is constructed, and the reinforcement body There is a known construction method for constructing a large-section tunnel that becomes a branching / merging section inward.

  And as a construction method of a reinforcing body, for example, in Patent Document 1, a roof shield machine is started from a shield tunnel, and a plurality of roof shield tunnels are arranged at a predetermined interval around the branch junction part, thereby A method for constructing a shield roof tip receiver that surrounds and then forming an improved zone between the roof shield tunnels is disclosed.

JP 2006-70530 A

However, in the tunnel construction method described in Patent Document 1, the roof shield tunnel is constructed by starting the roof shield machine directly from the side wall portion of the shield tunnel, and thus has the following problems.
(1) Since the launch base of the roof shield machine is located in the shield tunnel, the work area for constructing the shield tunnel and the launch base of the roof shield machine are complicated in the tunnel of the shield tunnel. It tends to interfere with work.
(2) The roof shield tunnel is constructed so as to extend in the longitudinal direction of the planned construction area of the branch and merge part. When the roof shield machine is started from the side wall part of the shield tunnel, the roof shield tunnel is oriented in a direction perpendicular to the side wall part. After the excavation of the natural ground, it is necessary to change the direction by about 90 degrees in the longitudinal direction of the branch / merging part construction planned region, and thus linear management becomes complicated.

  This invention is made | formed in view of this subject, Comprising: The main objective is a workability | operativity, without complicating the branch merge part which two tunnels join with each construction of the said two tunnels. The object is to provide a construction method for a large section tunnel that can be well and efficiently constructed as a large section tunnel.

  In order to achieve such an object, the construction method of a large-section tunnel according to the present invention uses a reinforcing body around the area where the large-section tunnel is to be constructed in advance when constructing a branching junction where two tunnels join as a large-section tunnel. In the construction method of a large-section tunnel in which a large-section tunnel is constructed inside the reinforcement body after being enclosed, at least one of the two tunnels is positioned outside the planned construction area of the large-section tunnel From the side wall, the ground is excavated horizontally, and a start side pit construction process for constructing a start side pit of the small cross section shield excavator, and a small cross section shield excavator from the start side pit in the area where the large cross section tunnel is planned to be constructed Adjacent to a small-section tunnel construction step of constructing a plurality of small-section tunnels so as to dig up in the longitudinal direction and surround the circumference of the large-section tunnel construction planned area A reinforcing body construction step for constructing the reinforcing body using a small-sized tunnel, and in the starting side pit construction step, the starting side pit is spaced in the axial direction of the tunnel in which the starting side pit is constructed. It is characterized in that a plurality are constructed.

  According to the construction method of the above-described large-section tunnel, the start horizontal shaft becomes a work area related to the small-section tunnel construction process, so that a work area is secured separately from the work area related to the construction of each of the two tunnels. be able to. As a result, the small section tunnel construction process and the construction relating to each of the two tunnels can proceed simultaneously, and the construction efficiency of the whole construction can be improved.

  Furthermore, since the small cross-section shield excavator starts from the starting horizontal shaft in the longitudinal direction of the area where the large-section tunnel is planned to be constructed, compared to a case where the small cross-section shield excavator starts from the side wall of the tunnel, it is approximately 90 degrees during the excavation. No need to change direction. Thereby, since it is not necessary to plan complicated alignment when constructing a small section tunnel, the alignment management at the time of construction becomes easy.

  The construction method of the large cross-section tunnel of the present invention is the large cross-section tunnel construction plan area, the small cross-section tunnel constructed from the start side pit located in the vicinity of the large cross-section tunnel construction plan area among a plurality of the start side pits The small cross-section tunnel constructed from the start horizontal shaft located at the side of the large cross-section tunnel construction planned area is constructed to be arranged at the top or bottom of the large cross-section tunnel construction planned area. It is characterized by.

  According to the construction method of the large cross section tunnel, the small cross section tunnel disposed at the top or bottom of the large cross section tunnel construction area is an axis extending from the starting horizontal shaft to the large cross section tunnel construction area. A long distance can be secured. This makes it possible to keep the bending angle in the height direction of the small cross-section tunnel small even when the height difference between the start horizontal shaft and the top or bottom of the large cross-section tunnel construction planned area is large.

  The construction method of a large-section tunnel according to the present invention is characterized in that, in the small-section tunnel construction step, a plurality of the small-section tunnels are constructed from one starting lateral shaft.

  According to the construction method of the large-section tunnel described above, the missing portion of the side wall portion is only the construction position of the start side pit in the one tunnel. Thereby, compared with the case where the said small cross-section shield machine starts from a side wall part, it becomes possible to reduce the defect | deletion location of this side wall part significantly.

  The construction method of a large cross-section tunnel according to the present invention is characterized in that, in the start side pit construction step, a plurality of start side pits are constructed in outer regions at both ends of the large cross-section tunnel construction planned region.

  According to the construction method of the large-section tunnel described above, it is possible to disperse and arrange a plurality of starting lateral shafts in a wide area across the planned area for constructing the large-section tunnel. Thereby, it can avoid that the missing part of the tunnel by building this starting horizontal shaft concentrates in a part of axial direction, and it is easy to ensure the soundness of the main tunnel.

  In the construction method of the large cross-section tunnel of the present invention, in the start side pit construction step, a plurality of the start side pits constructed in the outer region on one end side in the region where the large cross-section tunnel is planned to be constructed are constructed. A side wall in which a plurality of the starting horizontal shafts constructed in the outer region on the one end side are arranged on one of the both side wall portions of the tunnel and a plurality of the starting lateral shafts constructed in the outer region on the one end side are arranged It is characterized in that it is arranged on one of the side walls of the two tunnels different from the part.

  According to the construction method of the above-described large-section tunnel, the operation flow line from the tunnel pit to the starting horizontal pit is concentrated on one side or the other side of the both side walls of the tunnel. It is easy to secure the work flow line, and the workability of the two tunnels can be improved.

  In the construction method of a large cross-section tunnel according to the present invention, in the start side shaft construction step, a plurality of the start side shafts are shifted in the axial direction with respect to both side walls of the tunnel in which the start side shaft is constructed. It is characterized by arranging.

  According to the construction method of the above-described large-section tunnel, the working flow line for the starting horizontal shaft that extends from the inside of the tunnel to the starting horizontal shaft is also shifted in the axial direction of the tunnel. For this reason, even if the start side pit is constructed on both side walls of the tunnel, the work flow line for the start side pit does not break the axial work flow line for constructing the tunnel mine. It becomes possible to improve the workability related to the tunnel.

  In the construction method of the large cross-section tunnel of the present invention, the small cross-section tunnel constructed from the start lateral shaft is provided in the small cross-section tunnel construction step, and the start lateral shaft is provided in the large cross-section tunnel construction planned area. It is constructed so as to be arranged in a region covering the same side as the side.

  According to the construction method of the large-section tunnel described above, the horizontal bending angle of the small-section tunnel can be kept small. Thereby, since it becomes unnecessary to plan complicated alignment when constructing a small-section tunnel, alignment management during construction becomes easy.

  According to the present invention, a plurality of starting horizontal shafts are constructed in the direction that is horizontal and orthogonal to the axis of the one of the two tunnels, and smaller than the starting horizontal shaft. In order to construct a cross-section tunnel, there is no need to plan complicated alignment when constructing a small-section tunnel, and the starting horizontal pit becomes a work area related to the small-section tunnel construction process, Since there is no complication, it is possible to construct a branching junction where two tunnels join as a large-section tunnel with good workability and efficiency.

It is a top view which shows the branch merge part which the main line tunnel and branch tunnel of this invention join. It is sectional drawing of the large section tunnel construction plan area. It is a perspective view of a small section tunnel surrounding a large section tunnel construction planned area. It is a top view which shows the state which shifted and arranged the some start side pit in the axial direction of a main line tunnel in the both-sides wall part of a main line tunnel. It is a top view which shows the work flow line in a start side pit and a main tunnel tunnel in the case where a some start side pit is arrange | positioned and shifted in the axial direction of a main line tunnel. It is a top view which shows the state which aggregated and arrange | positioned the several start horizontal shaft to one side wall part of a main line tunnel. It is a top view which shows the operation | movement flow line in the start side pit and a main line tunnel mine in the case of arrange | positioning a several start side pit collectively on one side wall part. It is a perspective view which shows the state which constructed | assembled the several start horizontal shaft in the outer area | region of each both ends in the large-section tunnel construction plan area. It is a perspective view which shows the state which constructed | assembled the some start side pit on the side wall of a branch tunnel. It is a perspective view which shows the state which constructed | assembled the several start horizontal shaft in each of both a main line tunnel and a branch tunnel.

  The construction method of the large section tunnel of the present invention will be described with reference to FIGS.

As shown in the plan view of FIG. 1, the present invention is a construction method for constructing a branch junction where a main tunnel 1 and a branch tunnel 2 are joined as a large-section tunnel 3.
The main tunnel 1 and the branch tunnel 2 are not limited to new or existing structures, but in the present embodiment, a case of newly installing with a known shield excavator (not shown) is taken as an example. explain.

  The large section tunnel 3 to be constructed by the method of the present invention is constructed by forming a widened portion 11 in a part of the main tunnel 1 as shown in the plan view of FIG. The widened portion 11 has a shape in which the cross section of the point where the main tunnel 1 and the branch tunnel 2 are joined is formed to have the largest diameter, and gradually decreases in diameter in the axial direction and is attached to the main tunnel 1. Yes.

  In constructing such a large-section tunnel 3, in the construction method of the present invention, the periphery of the large-section tunnel construction planned region 4 is surrounded by a reinforcing body 5 in advance. After that, the main tunnel 1 located in the large-section tunnel construction planned region 4 is widened and the widened portion 11 is constructed to construct the large-section tunnel 3.

As shown in the cross-sectional view of FIG. 2, the reinforcing body 5 includes a plurality of small cross-sectional tunnels 6 and a ground improvement portion 7 that connects them. The small section tunnel 6 is constructed by a known small section shield excavator (not shown) such as a roof shield machine.
Below, the procedure for constructing the reinforcing body 5 described above is shown.

First, the starting horizontal shaft construction process will be described below.
As shown in the plan view of FIG. 1 and the perspective view of FIG. 3, from the side wall portion located outside the large-section tunnel construction planned area 4 in the main tunnel 1 toward the direction that is horizontal and orthogonal to the axis of the main tunnel 1. Excavate the natural ground and construct the start horizontal shafts 8, 8 '. In the present embodiment, the start horizontal shafts 8 and 8 'are constructed on the side wall portion of the main tunnel 1 located in a region where the branch tunnel 2 is not provided. However, the present invention is not necessarily limited to this. Starting lateral shafts 8 and 8 'may be constructed on the side wall portion of the main tunnel 1 located in a region where the main tunnel 1 is located.

  The excavation method of the start lateral shafts 8 and 8 'is not particularly limited, and any method may be used. For example, existing excavation methods such as a blade-type propulsion method conventionally used when constructing a horizontal shaft for connecting adjacent tunnels can be applied.

  A plurality of the above-described starting horizontal shafts 8 and 8 ′ are constructed at intervals in the axial direction of the main tunnel 1.

  In the present embodiment, the start horizontal shafts 8 and 8 'are constructed on both side walls of the main tunnel 1, but the positions are shifted in the axial direction of the main tunnel 1 as shown in the plan views of FIGS. Deploy. In such a so-called staggered arrangement, as shown in FIG. 5, the start horizontal shaft working flow lines 9 and 9 ′ for constructing the start horizontal shafts 8 and 8 ′ are also connected to the main line in the main tunnel 1. The position is shifted in the axial direction of the tunnel 1.

  For this reason, even if the start lateral shafts 8 and 8 'are constructed on both side walls of the main tunnel 1, the underground tunnel is not blocked by the start lateral shafts 9 and 9', and the main tunnel 1 is constructed. It is possible to secure the main work flow line 10 for performing the work without confusion with the start horizontal shaft work flow lines 9 and 9 '. Thereby, since it is not necessary to interrupt the mine work of the main tunnel 1 even during the construction of the start horizontal shaft construction process, the shield excavator that constructs the main tunnel 1 can construct the start horizontal shaft 8, 8 ′. Once the planned area has been excavated, the construction for constructing the start horizontal shafts 8 and 8 'can be started at any construction stage.

  The plurality of starting horizontal shafts 8 and 8 ′ may be constructed so that the height positions thereof are the same, or may be constructed by shifting the height. In addition, the axial arrangement interval of the start horizontal shafts 8 and 8 'can be constructed at any interval as long as the minimum distance for constructing the small-section tunnel 6 described later in a necessary linear shape is secured. Good.

Next, the small section tunnel construction process will be described.
As shown in the perspective view of FIG. 3, the small-section shield excavator is sequentially started by using the start side shafts 8 and 8 ′ of the plurality of start side shafts 8 and 8 ′ as the start base. The cross section tunnel 6 is constructed so as to extend in the longitudinal direction of the large cross section tunnel construction planned region 4.
In the small cross-section tunnel construction process, the start lateral shaft work flow lines 9 and 9 ′ become the work flow lines when working at the start horizontal shafts 8 and 8 ′.

  The small-section shield excavator is started from the plane perpendicular to the axial direction of the main tunnel 1 in the start lateral shafts 8 and 8 ′ toward the large-section tunnel construction planned region 4. When the small cross-section shield excavator is started from the start horizontal shafts 8 and 8 'in this way, the direction change operation of about 90 degrees required when starting from the side wall of the main tunnel 1 can be omitted. Is a simple linear shape as shown in the perspective view of FIG. 3, and accordingly, the linear management becomes easy and the construction efficiency is improved.

  The small-section shield excavator uses a known excavator, and includes, for example, an excavator body having a cutter head, a screw conveyor and a skin plate installed behind the excavator body.

  The excavator body equipped with the cutter head with the skin plate remaining in the state where the excavation is stopped after the excavation to the length exceeding the planned area 4 for constructing the large-section tunnel with the small-section shield excavator is left via the small-section tunnel 6 Then move backward toward the starting horizontal shaft 8, 8 'and collect it.

In the recovery of the excavator body described above, the recovery method may be a known method that has been practiced in the past, such as at a site where a reaching shaft cannot be provided.
For example, a screw conveyor installed behind the excavator body is dismantled and collected at the start side shafts 8 and 8 ′ via the small section tunnel 6. Next, the connection between the skin plate and the excavator main body is released, the excavator main body can be moved rearward, and the excavator main body is recovered from the start lateral shaft 8, 8 ′ via the small cross-sectional tunnel 6. Carry in the device. The excavator body is pulled by the recovery device and recovered to the start side shaft 8, 8 'side.

Thereafter, in the starting horizontal shafts 8 and 8 ′, the recovered excavator body is reused to assemble a new small-section shield excavator, and a new small-section tunnel 6 is constructed in parallel with the small-section tunnel 6.
In addition, the collection | recovery method of a small cross-section shield excavator is not necessarily limited to said method. For example, a reaching pit may be provided at a position beyond the large-section tunnel construction planned region 4 and the small-section shield excavator that has finished excavating the small-section tunnel 6 may be collected from the reaching pit.

In the present embodiment, as shown in the plan view of FIG. 4, two or three small-section tunnels 6 are constructed by using one starting lateral shaft 8, 8 ′. As described above, since a plurality of small cross-sectional tunnels 6 are constructed from one starting lateral shaft 8 and 8 ', it is possible to greatly reduce the missing portions generated in the side wall portion of the main tunnel 1.
The number of small cross-sectional tunnels 6 constructed from one starting horizontal shaft 8, 8 ′ is not limited to the above-mentioned number, but the diameter of the small cross-sectional tunnel to be constructed and the starting horizontal shafts 8, 8 ′. What is necessary is just to determine suitably according to the extension length of.

  Although the number of small cross-section tunnels 6 required for enclosing the large cross-section tunnel construction planned region 4 is constructed by the above method, the construction order of the small cross-section tunnels 6 is not particularly limited. For example, the first small section tunnel 6 is constructed so as to be positioned at the bottom of the large section tunnel construction planned area 4. Next, a new small-section tunnel 6 is constructed adjacent to the previously constructed small-section tunnel 6 with an interval. In this way, when arranging a plurality of small cross-section tunnels 6 in parallel, the bottom of the large-section tunnel construction planned area 4 is constructed in advance, and sequentially built toward the side of the large-section tunnel construction planned area 4 Good.

  Further, as shown in the perspective view of FIG. 3, the small cross-sectional tunnel 6 disposed at the bottom of the large-section tunnel construction planned area 4 is located farther from the large-section tunnel construction planned area 4 among the plurality of starting lateral shafts 8. It is constructed by starting a small cross-section shield excavator from the starting horizontal shaft 8, 8 '. On the other hand, the small cross-section tunnel 6 arranged on the side of the large cross-section tunnel construction planned area 4 is started by starting the small cross-section shield excavator from the start lateral shafts 8 and 8 'close to the large cross-section tunnel construction planned area 4. To construct.

  This is because when the small cross-section tunnel 6 is extended and arranged at the bottom of the level difference between the starting horizontal shafts 8 and 8 ', the large cross-section is made easy to keep the bending angle in the height direction as small as possible to facilitate linear management. This is to ensure the distance between the tunnel construction planned area 4 and the starting horizontal shafts 8 and 8 '. This also applies to the case where the small-section tunnel 6 located at the top is constructed.

  Further, as shown in the perspective view of FIG. 3, the same construction of the large-section tunnel construction planned region 4 is made by the small-section shield excavator started from the start side pit 8 located on one side of both side walls of the main tunnel 1. A small section tunnel 6 is constructed which is arranged in a region covering the side. Similarly, it arrange | positions in the area | region which covers the same side of the large cross-section tunnel construction plan area | region 4 with the small cross-section shield excavator started from the start side pit 8 'located in the other end side among the both-side wall parts of the main tunnel 1. The small section tunnel 6 is constructed.

That is, in order not to cross the small cross-section tunnels 6 constructed from the start horizontal shafts 8 and 8 ′ on both sides of the main tunnel 1, a plurality of small cross-section tunnels 6 surrounding the large cross-section tunnel construction planned area 4 should be complicated. There can be no orderly arrangement. Thereby, the linear shape can also be made into the simple linear shape which suppressed the bending angle of the horizontal direction as much as possible.
The arrangement interval of the small-section tunnel 6 is optimal in consideration of the cross-sectional shape of the large-section tunnel construction planned area 4 and the rigidity required for the reinforcing body 5, the ground condition of the natural ground, work efficiency, economy, and the like. Place at intervals.

As described above, in the small cross-section tunnel construction process, the start horizontal shafts 8 and 8 ′ are not only used as starting bases for starting the small cross-section shield excavator, but also of the excavator body constituting the small cross-section shield excavator. Since it becomes a work area for carrying out all operations related to the construction of the small-section tunnel 6 such as collection and assembly of a new small-section shield excavator that reuses the excavator body, the construction of the small-section tunnel 6 The work can be performed independently of the underground work of the main tunnel 1.
In addition, in the small cross-section tunnel construction process, the work flow lines 9 and 9 ′ for the start horizontal shafts become work flow lines when working on the start horizontal shafts 8 and 8 ′, and the work for constructing the main tunnel 1 is performed. It does not interfere with the main line work flow line 10.

Finally, the reinforcing body construction process will be described.
After the construction of the plurality of small cross-section tunnels 6, as shown in the cross-sectional view of FIG. 2, the reinforcing body 5 that surrounds the large-section tunnel construction planned region 4 by providing the ground improvement portion 7 between the adjacent small cross-section tunnels 6. To construct.

  Although the construction method of the ground improvement part 7 is not specifically limited, For example, the ground improvement material should just be inject | poured from the small cross-section tunnel 6 toward a natural ground. These operations may be performed after the large-section tunnel construction planned region 4 is surrounded by a plurality of small-section tunnels 6, but the procedure is not particularly limited.

  For example, the ground improvement unit 7 may be constructed every time a new small-section tunnel 6 is constructed with an interval next to the previously constructed small-section tunnel 6. According to such a procedure, since the small-section tunnel construction process and the reinforcement body construction process can be performed simultaneously, it is possible to improve the construction efficiency related to the construction of the reinforcement body 5.

In addition, the reinforcing body 5 is constructed so as to have sufficient rigidity to ensure the stability of the large-section tunnel construction planned region 4, and if it has at least a soil retaining function and a water stopping function, it is not always necessary. It is not limited to the above configuration.
For example, without providing the ground improvement body 7, the adjacent small cross-section tunnels 6 are constructed so as to partially overlap each other, thereby constructing a cross-section cylindrical body surrounding the large cross-section tunnel construction planned area 4 and reinforcing it. The body 5 may be used. Moreover, the cross-section cylindrical body surrounding the large cross-section tunnel construction planned region 4 constructed by connecting the adjacent small cross-section tunnels 6 to each other by the structure, and the outer periphery of the cross-section cylindrical body You may construct | assemble with the ground improvement body 7 to construct | assemble.

  The main tunnel 1 located in the large-section tunnel construction planned area 4 is widened and widened inside the reinforcement body 5 constructed through the above-described start horizontal shaft construction process, small-section tunnel construction process, and reinforcement body construction process. 11 is constructed to construct the large section tunnel 3.

  In addition, the construction method of the large-section tunnel of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in this embodiment, in the start horizontal shaft construction process, the start horizontal shafts 8 and 8 ′ are constructed by shifting the positions in the axial direction of the main tunnel 1 with respect to both side wall portions of the main tunnel 1. The arrangement is not limited.
As shown in the plan view of FIG. 6, it may be arranged in one of the both side walls of the main tunnel 1. When arranged in this way, as shown in the plan view of FIG. 7, the operation line 9 for the start horizontal shaft is also concentrated on the side where the start horizontal shaft 8 of the main tunnel 1 is constructed. 10 is easy to secure.

  In the present embodiment, in the start side pit construction step, the start side pits 8 and 8 ′ are constructed outside the large-section tunnel construction planned area 4 and on the side where only the main tunnel 1 is constructed. It is not necessarily limited to this.

  For example, as shown in the perspective view of FIG. 8, a plurality of starting lateral shafts 8, 8 ′ are constructed outside each of both ends of the large cross-section tunnel construction planned region 4 so as to sandwich the large cross-section tunnel construction planned region 4. In this case, when the shield excavator for constructing the main tunnel 1 has finished excavating the construction planned area of the start side pit 8 outside the one end side in the large section tunnel construction planned area 4, Construction work of the start horizontal shaft 8 is started. At this time, the shield excavator continues the excavation without interruption, and when the excavation is completed on the outer side of the other end side in the large-section tunnel construction planned area 4 and the construction planned area of the start horizontal shaft 8 ′ is finished, Start construction work of the start horizontal shaft 8 'in the area.

Moreover, in the perspective view of FIG. 8, the starting horizontal shaft 8 constructed | assembled in the outer area | region of the one end side in the large-section tunnel construction plan area | region 4 is arrange | positioned in one side among the both-sides wall parts of the main line tunnel 1, Although the start horizontal shaft 8 'constructed in the outer region of the other end portion in the construction planned region 4 is arranged on the other side of the both side wall portions of the main line tunnel 1, it is not limited to this.
As shown in the perspective view of FIG. 4, a plurality of starting horizontal shafts 8, 8 ′ that are shifted in the axial direction of the main tunnel 1 with respect to both side wall portions of the main tunnel 1 are arranged in the large-section tunnel construction planned region 4. You may build in the outer area | region of each both ends.

  Further, in the present embodiment, in the start side pit construction step, the case where a plurality of start side pits 8, 8 ′ are constructed on the side wall of the main tunnel 1 has been described in detail as an example. The construction position of 'is not limited to this. For example, as shown in FIG. 9, the branch tunnel 2 may be constructed together with the main tunnel 1, and a plurality of start lateral shafts 8 may be constructed on the side wall portion of the constructed branch tunnel 2. Moreover, the start horizontal shaft 8 constructed | assembled in the outer area | region of the one end side in the large cross-section tunnel construction plan area 4 is arrange | positioned in one side among the both-sides wall parts of the main line tunnel 1, and the other end in the said large cross-section tunnel construction plan area 4 As shown in FIG. 10, the side wall on one side of the side wall portions other than the side wall portion on which the start side shaft 8 is constructed, for example, as shown in FIG. You may build in the part.

  The construction method of the large cross-section tunnel of this embodiment is that the start side pit 8, 8 'is constructed in the start side pit construction process, and the start side pit 8, 8' is small in the small cross section tunnel construction process. A cross-sectional tunnel 6 is constructed. For this reason, it is not only necessary to plan a complicated alignment when constructing the small section tunnel 6, but the work related to the construction of the small section tunnel 6 can be carried out completely independently from the underground work of the main tunnel 1. Therefore, it is possible to construct the branch junction where the main tunnel 1 and the branch tunnel 2 join as the large-section tunnel 3 with good workability and efficiency.

DESCRIPTION OF SYMBOLS 1 Main tunnel 2 Branch tunnel 3 Large section tunnel 4 Large section tunnel construction plan area 5 Reinforcement body 6 Small section tunnel 7 Ground improvement part 8 Start side pit 8 'Start side pit 9 Start side pit work flow line 10 Main line work movement Line 11 Widening part

Claims (7)

When constructing a branching junction where two tunnels join as a large cross-section tunnel, first enclose the area where the large cross-section tunnel is planned to be built with a reinforcement, and then construct the large cross-section tunnel inside the reinforcement In the construction method of the large section tunnel
A starting horizontal shaft for excavating a natural ground horizontally from a side wall portion of the at least one of the two tunnels located outside the region where the large section tunnel is to be constructed, and constructing a starting horizontal shaft of a small section shield excavator Mine construction process,
A small cross-section tunnel excavator is excavated from the starting horizontal shaft in the longitudinal direction of the large-section tunnel construction planned area, and a plurality of small-section tunnels are constructed so as to surround the large-section tunnel construction planned area. Cross-section tunnel construction process,
A reinforcing body construction step of constructing the reinforcing body using the adjacent small-section tunnel,
A construction method of a large-section tunnel characterized in that, in the starting side pit construction step, a plurality of the starting side shafts are constructed at intervals in the axial direction of the tunnel in which the starting side pit was constructed.   In the small cross-section tunnel construction step, the small cross-section tunnel constructed from the start side pit located in the vicinity of the large cross-section tunnel construction plan area among the plurality of start lateral shafts, the side of the large cross-section tunnel construction plan area And the small cross-section tunnel constructed from the start lateral shaft located remotely from the large-section tunnel construction planned area is constructed so as to be arranged at the top or bottom of the large-section tunnel construction planned area. The construction method of the large-section tunnel according to claim 1.   3. The construction method of a large cross-section tunnel according to claim 1 or 2, wherein, in the small cross-section tunnel construction step, a plurality of the small cross-section tunnels are constructed from one starting lateral shaft.   The said start horizontal shaft construction process WHEREIN: The said some start horizontal shaft is constructed in the outer area | region of each both ends of the said large cross section tunnel construction plan area, The any one of Claim 1 to 3 characterized by the above-mentioned. Construction method for large section tunnels.   In the starting side pit construction step, a plurality of the starting side shafts constructed in an outer region on one end side in the large-section tunnel construction planned region are arranged on one of both side walls of the tunnel in which the starting side shaft is constructed. And the two tunnels constructed in the outer region on the other end side are different from the side wall portion in which the plurality of launch lateral shafts constructed in the outer region on the one end side are arranged. The construction method for a large-section tunnel according to claim 4, wherein the construction method is arranged on any one of the side wall portions.   In the starting horizontal shaft construction step, a plurality of the starting horizontal shafts are arranged with their positions shifted in the axial direction of the tunnel with respect to both side walls of the tunnel in which the starting horizontal shaft is constructed. Item 5. A construction method for a large-section tunnel according to any one of Items 1 to 4.   In the small cross-section tunnel construction step, the small cross-section tunnel constructed from the starting horizontal shaft is arranged in a region covering the same side as the side where the starting horizontal shaft is provided in the large-section tunnel construction planned region. The construction method of a large-section tunnel according to claim 5 or 6, wherein the construction method is constructed as described above.