JP2002227585A - Construction method for branched route tunnel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a ramp way tunnel branched from a main route tunnel in a short period of time at low cost. SOLUTION: When the ramp way tunnel 21 is constructed in the main route tunnel 1, a width expanded part 4 whose digging width is expanded is integrally formed during digging of the main route tunnel 1 to excavate the ramp way tunnel 21 whose opening is connected to the width expanded part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the construction of a branch route tunnel such as a rampway, for example, for joining a branch route tunnel to a main route tunnel for roads or railroads, or for branching a branch route tunnel from the main route tunnel. About the method.

[0002]

2. Description of the Related Art For example, as a conventional technique for forming a ramp way tunnel that branches into a main tunnel for roads, a ramp weight tunnel is connected to the main tunnel by an open-cutting method, or a main tunnel and a ramp way tunnel are separately constructed. Kansashi method of connecting the two (Patent 2839
No. 440), a method of forming a middle wall or a side wall by using precast (Japanese Patent Application Laid-Open No. 2000-197788), and a method of performing an extended excavation using a support (Japanese Patent Application Laid-Open No. 10-280861)
No.).

[0003]

However, in the open-cutting method, it is difficult to select an opening on the ground side, and in other methods, the connection portion has a cross-section that spreads in a cross-sectional direction. There was a problem that the reinforcement in the vicinity became large and the construction period was prolonged and the cost was likely to increase.

An object of the present invention is to solve the above-mentioned problems and to provide a method of constructing a branch route tunnel in which a branch route tunnel can be formed in a main route tunnel in a short period of time and at low cost, and the construction cost can be reduced. .

[0005]

In order to achieve the above object, according to the present invention, when a branch route tunnel is provided in a main route tunnel, the branch route tunnel is excavated during the excavation of the main route tunnel.
A widened portion having an increased excavation width is integrally formed, and a branch route tunnel that is opened and connected to the widened portion is excavated.

According to the above configuration, the branch route tunnel is formed by using the widened portion formed in advance, so that the connection work of the branch route tunnel can be performed in comparison with the case where the connection work is performed in the normal portion of the main route tunnel. It can be implemented easily and in a short period of time, and the extended route portion that reaches the branch route can be formed using the widened portion. Therefore, the branch route tunnel can be formed at low cost and in a short period of time.

According to a second aspect of the present invention, in the method of the first aspect, the branch line tunnel is formed by connecting the branch shield excavator from the widened portion to the start or the widened portion.

According to the above configuration, the branch shield machine can be assembled and disassembled in the widened portion having a large excavation width, so that the connecting operation can be performed quickly and easily.

The invention described in claim 3 is the first or second invention.
In the method described above, the branch route tunnel is connected to the widened portion at a predetermined angle from a direction perpendicular to the main route tunnel.

According to the above configuration, the connection operation and the operation associated with the arrival of the branch shield excavator can be facilitated by inclining the connection direction of the branch route tunnel.

According to a fourth aspect of the present invention, when the branch shield tunneling machine is started from the main route tunnel to excavate the branch route tunnel, the connecting portion of the branch route tunnel is excavated while the main shield tunneling machine excavates the main route tunnel. Forming a widened portion in which the connection side is expanded and excavated, a reinforcing member for reinforcing an opening corresponding to a cross section of the branch route tunnel is installed on the inner surface of the widened portion side wall, and the side wall of the opening is removed to branch off. The shield excavator is started.

[0012] According to the above configuration, since the cross section of the excavation is greatly expanded at the junction of the branch line tunnel, it is necessary to strongly reinforce the lining body. When installed in a branch route tunnel, the line width in the tunnel is limited, and when installed outside the tunnel, the construction period and costs are prolonged and increased. In the present invention, by forming the widened portion in the main route tunnel in advance, the reinforcing member can be installed in the widened portion to reliably reinforce the lining body. Therefore,
The branch line tunnel formed by starting the branch shield excavator from the main line tunnel can be reinforced and connected well without reducing the width of the main line tunnel,
The branch route tunnel can be connected and constructed in a short period of time and at low cost.

According to a fifth aspect of the present invention, in the configuration according to the fourth aspect, after the reinforcing member is installed, a starting cylinder capable of starting a branch shield excavator is installed on the reinforcing member, and the ground outside the widening portion is provided. After reinforcing the side wall, the side wall of the opening is removed, a branch shield excavator is started from the starting cylinder to excavate the branch line tunnel, and the lining body of the branch line tunnel is connected to the side wall of the main line tunnel. is there.

[0014] According to the above structure, the branch line tunnel can be easily and reliably connected to the main line tunnel even in the case of collapsed ground or ground with a large amount of groundwater by improving the soil quality of the connecting portion. The starting cylinder allows the branch shield excavator to start stably from the widened portion of the main route tunnel.

According to a sixth aspect of the present invention, the side wall where the branch line tunnel is connected and opened at the widened portion is formed of a lining material excavable by a branch shield excavator, and the side wall is formed by the branch shield excavator. It is started by excavating directly.

According to the above configuration, since the side wall of the widened portion can be directly excavated by the branch shield excavator, the improvement of the surrounding ground can be greatly reduced, and the construction period is shortened and the cost is reduced. Can be.

According to a seventh aspect of the present invention, when the branch shield excavator is started from the ground side or another tunnel to excavate the branch route tunnel and reach the main route tunnel,
While the main line tunnel was being excavated by the main shield machine,
A side where the branch route tunnel reaches is formed with a widened portion that is expanded and excavated, and a reinforcing member that reinforces an opening corresponding to a cross section of the branch tunnel is installed on an inner surface of the widened portion side wall to reinforce the opening. The member is removed to reach the branch shield machine.

According to the above construction, since the excavation cross section is greatly expanded at the junction of the branch route tunnel, it is necessary to strongly reinforce the lining body. When installed in a branch route tunnel, the line width in the tunnel is limited, and when installed outside the tunnel, the construction period and costs are prolonged and increased. In the present invention, by forming the widened portion in the main route tunnel in advance, the reinforcing member can be installed in the widened portion to reliably reinforce the lining body. Therefore,
The branch route tunnel formed by reaching the main route tunnel by launching the branch shield excavator from the outside can be reinforced and connected well without reducing the width of the main route tunnel by the reinforcing member in the widening part. The branch line tunnel can be connected and constructed in a short period of time and at low cost.

According to an eighth aspect of the present invention, in the configuration of the seventh aspect, after the reinforcing member is installed, a reaching cylinder through which the branch shield excavator can enter is installed on the reinforcing member, and the ground outside the widening portion is provided. After the reinforcement, the side wall of the opening is removed, the branch shield machine is reached from the opening into the arrival cylinder, the branch line tunnel is connected, and the lining body of the branch line tunnel is changed to the lining body of the main line tunnel. It is something that connects.

[0020] According to the above structure, the branch line tunnel can be easily and reliably connected to the main line tunnel even in the case of collapsed ground or ground with a large amount of groundwater by improving the soil quality of the connecting portion. The reaching cylinder allows the branch shield machine to stably reach the widened portion of the main route tunnel.

According to a ninth aspect of the present invention, the side wall to which the branch line tunnel is connected and opened at the widened portion is formed of a covering material excavable by a branch shield excavator, and the side wall is formed by the branch shield excavator. It is reached by direct excavation.

According to the above construction, the side wall of the widened portion can be directly excavated by the branch shield excavator, so that the improvement of the surrounding ground can be greatly reduced, thereby shortening the construction period and promoting cost reduction. Can be.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for constructing a branch route tunnel according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, reference numeral 1 denotes a main tunnel excavated by the main shield machine 2 (main line tunnel).
For example, a circular cross section (a rectangular cross section or an elliptical cross section may be used)
And is covered with a segment (lining body) 3. The rampway tunnel (branch route tunnel) 21 connected to the main tunnel 1 has a circular cross section (a rectangular cross section or an elliptical cross section may be used), and is excavated by a branch shield excavator 22 started from the main tunnel 1, for example. .

In the connection section 23 of the rampway tunnel 21 in the main line tunnel 1, a widened section 4 having an oval (elliptical) cross-section, which extends by a predetermined width W, is formed on the connection side. The widening portion 4 is formed over a range including the deceleration branching section, the acceleration merging section, or the emergency stop section of the rampway and the connecting portion. For example, the connecting portion 23 is set near the end of the widening portion 4.

The main shield machine 2 that excavates the widened portion 4 simultaneously with the main line tunnel 1 is capable of excavating the widened portion 4 simultaneously with the excavation of the main line tunnel 1. For example, a copy cutter mounted on a cutter head is projected only at a predetermined portion. However, since a sufficient widening width cannot be obtained, a widening type main shield machine 2 having a drilling device shown in FIG. 5, for example, is used here.

That is, the excavator of the main shield machine 2 comprises a cutter head S rotatably arranged at the front of the shield body and a ruler triangle having three apexes C1 to C3 at the apexes of the triangle. During normal excavation, the rotation axis Os and the shield axis Oc are made to coincide with each other to rotate and drive Rc to form a circular tunnel Tc having a diameter b. Further, at the time of widening excavation, the cutter head S is moved from the shield axis Oc to the rotation axis Os to rotate the cutter head S, and the cutter head S is rotated around the revolution axis Od eccentric from the shield axis Oc.
Then, the elliptical tunnel Te having the major axis a and the minor axis b is excavated with the rotation direction of the revolution drive Rd and the rotation drive Rc being the same direction and the rotation speed ratio being 3: 1. Here, the rotation axis Os of the cutter head S is moved on the major axis so that the end of the circular tunnel Tc is in contact with the end of the circular tunnel Tc. A retractable movable cutter (not shown) is attached to the tops C1 to C3 of the cutter head S so that the diameter of the circular section tunnel Tc and the minor axis of the oval section tunnel Te are each equal to b. ing.

At the bottom of the main line tunnel 1, there is formed a transport surface 7 capable of transporting a branch starting member or the like via a carriage 10, and the widening portion 4 is greatly expanded by the connection of the rampway tunnel 21. A reinforcing frame (reinforcing member) 5 for reinforcing the transverse section of the side wall 3a is installed in connection with the inner surface of the side wall 3a. The reinforcing frame 5 is constructed of a high-strength steel material by welding, bolts, or the like, and has a central portion provided with an opening 6 for connecting a rampway tunnel 21.

A starting cylinder 8 is provided in the opening 6 of the reinforcing frame 5.
Are fitted and fixed by welding.
The branch shield machine 22 for excavating the rampway tunnel 21 can be started. The exit of the starting cylinder 8 is arranged in contact with or close to the inner surface of the side wall 3a, and is provided with an entrance packing for sealing a gap with the branch shield excavator 22 when starting. Start cylinder 8
At the entrance of the vehicle, a starting frame 9 is installed on a bogie 10 via a revolving floor plate 10a, on which a branch shield excavator 22 is mounted.
Are positioned and fixed, and a reaction force receiving member (not shown) for receiving a starting reaction force is provided.

In the connecting portion 23, in order to prevent the collapse of the ground and the inflow of earth and sand, the widened portion 4 is formed around the outer periphery of the reinforcing frame 5.
The chemical liquid injection pipe 11 is penetrated into the ground at a predetermined pitch to a predetermined depth by boring from the side wall 3a of the ground or from the ground side, and the chemical liquid (reinforcing material) is injected into the ground outside the side wall of the widened portion to show the soil shown by cross-hatching. A soil improvement device (ground reinforcement means) 12 for hardening and improving the ground of the improvement unit 13 is provided. In addition, instead of the soil improvement by injecting a chemical solution, a ground reinforcing means such as an injection device of a strength material (for example, concrete) for improving the ground strength can be used.

The segment 3 corresponding to the connection 23
Of the side wall 3a is formed in a segment structure that can be easily removed, or one that has low strength and is easily broken. Further, a fitting hole or a pipe of the chemical solution injection pipe 11 is formed in the segment 3 around the connection part 23 in advance.

Next, a method of constructing a branch route tunnel will be described. . The main tunnel 1 is excavated by the main shield machine 2 to form a widened portion 4 excavated over a predetermined range including a traveling portion for acceleration or deceleration at a connecting portion 23 of the rampway tunnel 21.

[0033] After the completion of the excavation of the main line tunnel 1 or the excavation of the predetermined section, the components of the reinforcing frame 5 are carried into the widened portion 4 and assembled and installed on the inner surface of the side wall 3a. Further, the starting cylinder 8 is carried in and connected and fixed to the reinforcing frame 5.
Further, the starting stand 9 is carried in, and the respective components of the branch shield excavator 22 divided into blocks, assembled with bolts, and divided into small parts are carried in and assembled, and installed on the starting stand 9. In addition, the starting frame 9 may be installed on a carrier (not shown) that transports the components of the branch shield machine 22 to the assembly position.

[0034] A chemical liquid injection pipe 11 penetrates into the ground near the periphery of the reinforcing frame 5 and penetrates into the ground, and a ground improvement agent is injected from the ground improvement device 12 to prevent inflow of earth and sand and muddy water when the ground is cut. The soil improvement unit 13
The ground is solidified.

[0035] The segment 3 forming the side wall 3a of the opening 6 is removed or broken away from the starting cylinder 8, the reaction support is installed on the starting base 9, the branch shield excavator 22 is started, and the ground is improved from the soil improvement section 13. Drilling and segment 2
4 and the base end of the segment 24 is connected and fixed to the segment 3 of the main line tunnel 1 and the reinforcing frame 5. The reinforcing frame 5 may be used as it is by embedding it in the widened portion 4 or, if it becomes an obstacle to traffic, a temporary reinforcing work may be performed after the penetration, and a removal may be performed to perform the main reinforcing work.

According to the above embodiment, the main tunnel 1
In the connecting portion 23 of the rampway tunnel 21, a widened portion 4 is excavated and formed in advance, and the reinforcing frame 5 is installed on the inner surface of the side wall 3 a of the widened portion 4. The segment 3 of the expanded connecting portion 23 can be reinforced with high strength. Therefore, since the widened portion 4 is provided in the main tunnel 1 in advance, the connecting portion 23 is provided.
The cross section of the main tunnel 1 can be secured widely, and the assembling work and connection construction of the branch shield excavator 22 can be easily performed. Further, a traveling portion for acceleration and deceleration can be secured in advance, so that widening excavation in a later process can be performed. It becomes unnecessary. In order to reinforce the connecting portion 23, the inside of the main tunnel 1 and the rampway tunnel 21
Since the inside is not restricted and the reinforcement can be performed in a short time and at a low cost, the connection work of the rampway tunnel 21 can be formed in a short time and at a low cost. After the soil is improved by injecting a chemical solution into the ground outside the widened portion 4 by the soil improvement device 12, the side wall facing the opening of the reinforcing member is removed, and the branch shield excavator is started. By improving the soil quality of the portion 23, a tunnel can be easily and reliably connected even to a collapsed ground or a ground with a lot of groundwater.

Next, another embodiment of a method for constructing a rampway tunnel which joins the main tunnel 1 will be described with reference to FIG. The same members as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0038] The main tunnel 1 is excavated by the main shield machine 2, and the connecting portion 23 of the rampway tunnel 21 is excavated.
Then, the widened portion 4 excavated over a predetermined range is formed including the merging traveling portion for acceleration or deceleration.

[0039] After the completion of the excavation of the main line tunnel 1 or the excavation of the predetermined section, the chemical liquid injection pipe 11 is first penetrated into the ground by penetrating the peripheral side wall 3a of the reinforcing frame 4, and the ground improvement agent is injected from the ground improvement device. The soil improvement section 13 prevents soil and muddy water from flowing into the main tunnel 1 when excavating.
The ground is solidified.

[0040] The members of the reinforcing frame 5 are carried into the widened portion 4 and assembled and installed on the inner surface of the side wall 3a. . A branch shield excavator 22 is launched from the ground side or another tunnel, approaches the connection part 23, and
Is reached, the search boring is performed from the main line tunnel 1 side, the arrival position of the branch shield excavator 22 is searched, and the opening position is marked. Then, the arrival cylinder 31 (having substantially the same structure as the starting cylinder 8) is installed corresponding to the opening position,
It is connected and fixed to the reinforcing frame 5.

[0041] Dig the branch shield excavator 22,
The soil improvement section 13 is excavated, and the segment 3 of the opening 6 is removed or broken away from the inside of the main tunnel 1 from a portion where the excavating cutter contacts the segment 3 of the opening 6, and the branch shield excavator 22 is further advanced. Then, the access platform 32 in the main line tunnel 1 from the opening 6 via the arrival tube 31
(Almost the same structure as the starting frame 9). Further, the branch shield machine 22 is disassembled and carried out, the segment 24 is assembled and the rampway tunnel 21 is lining,
The segment 24 is connected to the side wall 3 a around the opening 6 and the reinforcing frame 5 to connect the rampway tunnel 21 to the main line tunnel 1.

According to the above embodiment, the main tunnel 1
By forming the widened portion 4 in advance, the connection work of the rampway tunnel 21 can be easily carried out, and the reinforcing frame 5 is installed in the widened portion 4 to ensure the enlarged cross section. Can be reinforced. As a result, the rampway tunnel 21 excavated from the ground side or another tunnel can be satisfactorily reinforced and connected without reducing the cross-sectional width of the main tunnel 1, thereby shortening the construction period and connecting at low cost. Can be constructed.

In the above embodiment, the method of constructing the main road tunnel 1 and the rampway tunnel 21 has been described. However, the same applies to a tunnel for a railway such as a subway.

Further, in the above embodiment, the rampway tunnel 21 is formed in parallel with the widened portion 4, but may be connected to a tapered portion on the starting end or end side of the widened portion 4. In this case, instead of the reinforcement by the reinforcing member near the opening, a segment in which the opening is formed in advance may be assembled and used as the reinforcing member.

Further, in the above-described embodiment, the lining material of the tunnel which cannot be excavated by the shield machine is used. However, the lining material (segment etc.) which can be directly excavated by the shield machine is widened. By using the side wall of the portion in a predetermined area including the connection opening, the branch shield excavator can directly excavate the side wall to start or reach. As a result, the ground improvement around the connection portion can be minimized, so that the branch tunnel can be formed in a shorter time and at lower cost.

[0046]

As described above, according to the first aspect of the present invention, since the branch route tunnel is formed using the widened portion formed in advance, the connection work is performed in the normal portion of the main route tunnel. As compared with the above, the connection work of the branch route tunnel can be carried out easily and in a short period of time, and the extended route part reaching the branch route can be formed using the widened part,
A branch route tunnel can be formed at low cost and in a short period of time.

According to the second aspect of the present invention, since the assembling work and the disassembling work of the branch shield machine can be performed in the widened portion having a large excavation width, the connecting work can be performed quickly and easily.

According to the third aspect of the present invention, by inclining the connection direction of the branch route tunnel, the connection work and the work associated with the arrival of the branch shield excavator at the start can be facilitated.

According to the fourth aspect of the present invention, since the excavation cross section is greatly expanded at the junction of the branch route tunnel, it is necessary to strongly reinforce the lining body. If installed in a route tunnel or a branch route tunnel,
The line width in the tunnel will be limited, and if installed outside the tunnel, the construction period and costs will be prolonged and increased. In the present invention, by forming the widened portion in the main route tunnel in advance, the reinforcing member can be installed in the widened portion to reliably reinforce the lining body. Therefore, the branch line tunnel formed by starting the branch shield excavator from the main line tunnel can be reinforced and connected well without reducing the width of the main line tunnel. Can be used to connect the branch route tunnel.

According to the fifth aspect of the present invention, it is possible to easily and surely connect the branch route tunnel to the main route tunnel even in the case of collapsed ground or ground with much groundwater by improving the soil quality of the connection portion. Further, the branch shield excavator can be stably started from the widened portion of the main route tunnel by the starting cylinder.

According to the sixth aspect of the invention, since the side wall of the widened portion can be directly excavated by the branch shield excavator, the improvement of the surrounding ground can be greatly reduced, and the construction period is shortened and the cost is reduced. Can be promoted.

According to the seventh aspect of the present invention, since the cross section of the excavation is greatly expanded at the junction of the branch route tunnel, it is necessary to strongly reinforce the lining body. If installed in a route tunnel or a branch route tunnel,
The line width in the tunnel will be limited, and if installed outside the tunnel, the construction period and costs will be prolonged and increased. In the present invention, by forming the widened portion in the main route tunnel in advance, the reinforcing member can be installed in the widened portion to reliably reinforce the lining body. Therefore, the branch route tunnel formed by reaching the main route tunnel by starting the branch shield excavator from the outside is reinforced and connected well by the reinforcing member in the widening portion without reducing the width of the main route tunnel. It is possible to connect and construct a branch route tunnel in a short period of time and at low cost.

According to the eighth aspect of the present invention, the branch line tunnel can be easily and reliably connected to the main line tunnel even in the case of collapsed ground or ground with a large amount of groundwater by improving the soil quality of the connecting portion. Moreover, the branch shield shield machine can be stably made to reach the widened portion of the main route tunnel by the reaching cylinder.

According to the ninth aspect of the present invention, since the side wall of the widened portion can be directly excavated by the branch shield excavator, the improvement of the surrounding ground can be greatly reduced, and the construction period is shortened and the cost is reduced. Can be promoted.

[Brief description of the drawings]

FIG. 1 is an overall plan view illustrating an embodiment of a method for constructing a branch route tunnel according to the present invention.

FIG. 2 is a sectional view taken along the line AA shown in FIG.

FIG. 3 is a sectional view taken along the line BB shown in FIG.

FIG. 4 is a sectional view taken along the line CC shown in FIG.

FIG. 5 is a front view illustrating an excavator of a main shield machine used in the method of constructing the branch route tunnel.

FIG. 6 is an overall plan view for explaining another embodiment of the branch route tunnel construction method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main line tunnel 2 Main shield excavator 3 Segment 3a Side wall 4 Widening part 5 Reinforcement frame 6 Opening 8 Launching cylinder 11 Chemical liquid injection pipe 12 Soil improvement device 13 Soil improvement unit 21 Rampway tunnel 22 Branch shield excavator 23 Connecting part 24 segment

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Atsushi Takubo 2-2-2 Matsuzakicho, Abeno-ku, Osaka-shi, Osaka Prefecture Inside Okumura Gumi Co., Ltd. (72) Inventor Saburo Okuno 2-2-2 Matsuzakicho, Abeno-ku, Osaka-shi, Osaka No.2 Okumura Gumi Co., Ltd. 7-89 Hitachi Shipbuilding Co., Ltd. (72) Inventor Tadao Yoshikawa 1-7-89 Minami Kohoku, Suminoe-ku, Osaka-shi, Osaka F-term inside Hitachi Zosen Corporation 2D054 AA03 AA04 AA05 AC01 BA03 BA25 EA09 FA02

Claims (9)

[Claims] When a branch route tunnel is provided in a main route tunnel, a widened portion having an increased digging width is integrally formed during excavation of the main route tunnel, and the branch route is connected to the widened portion by an opening. A method for constructing a branch route tunnel, which comprises digging a tunnel. 2. The method for constructing a branch route tunnel according to claim 1, wherein the branch route tunnel is formed by connecting a branch shield machine from the widened portion to the start or the widened portion. 3. The method according to claim 1, wherein the branch route tunnel is inclined at a predetermined angle from a direction perpendicular to the main route tunnel and connected to the widened portion. 4. When the branch shield tunneling machine is started from the main route tunnel to excavate the branch route tunnel, the main shield tunneling machine excavates the main route tunnel.
Forming a widened portion in which the connection side is expanded and excavated over the connecting portion of the branch route tunnel, and a reinforcing member for reinforcing an opening corresponding to a cross section of the branch route tunnel is provided on an inner surface of the widened portion side wall; A method of constructing a branch route tunnel, comprising removing a side wall and starting a branch shield machine. 5. After the reinforcing member is installed, a starting cylinder capable of starting a branch shield machine is installed on the reinforcing member, and after reinforcing the ground outside the widened portion, a side wall of the opening is removed. 5. A branch route tunnel is excavated by starting a branch shield excavator from the starting cylinder, and a lining body of the branch route tunnel is connected to a side wall of the main route tunnel.
The construction method of the branch route tunnel described. 6. A side wall to which a branch line tunnel is connected and opened at a widening portion is formed of a lining material that can be excavated by a branch shield excavator, and the branch shield excavator directly excavates and starts the side wall. The method according to claim 4 or 5, wherein the branch route tunnel is constructed. 7. When a branch shield excavator is started from the ground side or another tunnel to excavate a branch route tunnel and reach the main route tunnel, the main shield tunnel machine excavates the main route tunnel.
A side where the branch route tunnel is reached is formed with a widened portion that is expanded and excavated, and a reinforcing member for reinforcing an opening corresponding to a cross section of the branch tunnel is installed on an inner surface of a side wall of the widened portion, and reinforcing the opening. A method for constructing a branch route tunnel, comprising removing a member to reach a branch shield machine. 8. A branch shield excavating machine is installed on the reinforcing member, a reaching cylinder through which a branch shield excavator can enter is installed, the ground outside the widened portion is reinforced, and a side wall of the opening is removed. The branch line tunnel according to claim 7, wherein the branch line tunnel is connected by allowing the machine to reach the inside of the arrival cylinder from the opening, and the lining body of the branch line tunnel is connected to the lining body of the main line tunnel. Construction method. 9. A side wall to which a branch line tunnel is connected and opened in the widening portion is formed of a lining material that can be excavated by a branch shield excavator, and the side wall is directly excavated by the branch shield excavator to reach. The method according to claim 7 or 8, wherein the branch route tunnel is constructed.