How to build a tunnel

Abstract

To provide a tunnel construction method that can suppress a prolonged construction period and the rise in construction costs.SOLUTION: A method of constructing a tunnel 1 provided underground from a wellhead 4a to a wellhead 4b comprises the steps of: constructing a part 1b of the tunnel 1 with a downward slope from the wellhead 4a using the propulsion method in which the tunnel 1 is excavated at a front end of an excavator, a propulsion pipe is connected to a rear part of an already assembled tunnel skeleton, and the tunnel skeleton is propelled forward to construct an underground pipeline; and constructing parts 1a and 1c of the tunnel 1 including at least the deepest part and on the other side of a wellhead 5a from the part 1a of the tunnel 1 by using the shield method in which the tunnel 1 is excavated at the front end of an excavator and a segment pipe is connected to the front part of the already assembled tunnel skeleton to construct the underground pipeline.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tunnel construction method. [Background technology]

[0002] Particularly in urban areas, when constructing a tunnel that passes under the pile foundations of existing structures such as levees or under rivers, it is common to drill start and arrival shafts to the construction depth of the tunnel, and then use a boring machine to construct a horizontal tunnel between these shafts.

[0003] A hybrid jacking method is known in which, when constructing a horizontal tunnel, a tunnel is constructed by starting from a starting shaft using a jacking method, and then the tunnel is constructed by switching to a shield method (see, for example, Patent Documents 1 and 2).

[0004] Incidentally, Patent Document 3 discloses, as a modified example of the shield tunneling method, a tunnel constructed from a starting shaft to a destination shaft by the shield tunneling method in the order of a downward gradient section, a horizontal section, and an upward gradient section. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 2693904 [Patent Document 2] Patent No. 5806186 [Patent Document 3] Japanese Patent Application Publication No. 2-269295 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the long side of the shaft (or its diameter if it is circular) must be at least as long as the total length of the excavator plus the launching equipment, and such a shaft must be constructed by digging deeper than the bottom of the pile foundation of the existing structure.

[0007] The deeper the shaft, the greater the load (earth pressure, water pressure) on the retaining wall around the shaft. Therefore, when constructing a deep shaft, the sheet piles and their reinforcing members must be made strong, and depending on the ground conditions, it may be necessary to install RC diaphragm walls. Therefore, constructing a deep shaft poses the problem of longer construction time and higher construction costs.

[0008] In view of the above, an object of the present invention is to provide a method for constructing a tunnel that can prevent the construction period from being extended and the construction costs from rising. [Means for solving the problem]

[0009] The tunnel construction method of the present invention is a tunnel construction method implemented by using a tunneling machine capable of performing a hybrid tunneling method that switches from a jacking method to a shield method when constructing a tunnel that passes under a pile foundation of an existing structure or a river, and starts from one of the tunnel entrances using the jacking method and With gradients of 10% to 45% a downward slope portion construction process for constructing a downward slope portion of a tunnel that descends underground; In the portion on the uphill side of the boundary between the downward slope portion and the horizontal portion, The method is characterized by comprising a horizontal section construction process in which a horizontal section that is connected to the deep part of the downward slope section is constructed by switching from the jacking method to the shield method, and an upward slope section construction process in which the shield method is started from the deep part of the horizontal section and the upward slope section of the tunnel is constructed up to the other tunnel entrance.

[0010] According to the tunnel construction method of the present invention, a part of the tunnel is constructed from one of the entrances at a downward gradient using the jacking method, so that it is possible to make the bottom position of the starting shaft where the entrance is formed shallower than in the techniques described in Patent Documents 1 and 2, or there is no need to form a starting shaft. Furthermore, since the tunnel on the other entrance side is constructed at an upward gradient using the shield method, it is possible to make the bottom position of the arrival shaft where the entrance is formed shallower than in the techniques described in Patent Documents 1 and 2, or there is no need to form an arrival shaft. As a result, it is possible to shorten the construction period and reduce the construction costs for forming the starting shaft and the arrival shaft, and ultimately to shorten the construction period and reduce the construction costs overall when constructing a tunnel.

[0011] In addition, when working on a downward slope where accidents such as groundwater seeping in or trolleys running away are likely to occur, using the jacking method makes it possible to operate the excavator unmanned, thereby increasing the safety of the work.

[0012] In the tunnel construction method of the present invention, for example, the one of the tunnel entrances may be formed in a departure shaft, and the other of the tunnel entrances may be formed in a arrival shaft. [Brief description of the drawings]

[0013] [Figure 1] 1 is a conceptual diagram illustrating a tunnel constructed by a tunnel construction method according to an embodiment of the present invention. [Diagram 2] 3 is a flowchart of a tunnel construction method according to an embodiment of the present invention. [Diagram 3] A conceptual diagram illustrating a method for laying gas pipes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A tunnel construction method according to an embodiment of the present invention will be described with reference to the drawings.

[0015] Referring to Figure 1, this construction method is suitable for constructing a tunnel 1 in an excavation-free manner in urban areas, for example, by bypassing pile foundations 2 of existing structures such as embankments and bridge girders, or a river 3 downward.

[0016] Here, a case will be described where a deep tunnel 1 is constructed for laying a gas pipe. The total horizontal length L of the tunnel 1 is, for example, 2000 m. The depth A of the horizontal portion 1a, which is the deepest part of the tunnel 1, is, for example, 50 m. Note that Figs. 1 and 3 are diagrams for conceptually explaining this embodiment, and the dimensions are exaggerated.

[0017] Referring to FIG. 2, this construction method includes a starting shaft construction process (STEP 1), a destination shaft construction process (STEP 2), a downward slope section construction process (STEP 3), a horizontal section construction process (STEP 4), an upward slope section construction process (STEP 5), a gas pipe laying process (STEP 6), and a backfilling process (STEP 7).

[0018] In the starting shaft construction step STEP 1, a starting shaft 4 is constructed on the ground. In the arrival shaft construction step STEP 2, an arrival shaft 5 is constructed on the ground.

[0019] The starting shaft 4 and the arrival shaft 5 may be constructed in the same manner as in the past, and detailed explanations will be omitted. Although not shown, a support stand for supporting the excavator is installed in the starting shaft 4, and a support stand for receiving the excavator is installed in the arrival shaft 5.

[0020] The depth B of the departure shaft 4 and the arrival shaft 5 is shallower than the depth A of the horizontal part 1a, which is the deepest part of the tunnel 1, and is, for example, 10 m. In the departure shaft 4, the shaft wall is excavated when the excavator starts, so that a shaft entrance 4a is formed that is inclined at the same gradient as the downward gradient part 1b described later, and this shaft entrance 4a corresponds to one of the shaft entrances of the present invention. On the other hand, in the arrival shaft 5, the shaft wall is excavated when the excavator arrives, so that a shaft entrance 5a is formed that is inclined at the same gradient as the upward gradient part 1c described later, and this shaft entrance 5a corresponds to the other shaft entrance of the present invention. In addition to the departure shaft 4 and the arrival shaft 5, it is not necessary to provide shafts such as intermediate shafts.

[0021] In the downward gradient section construction step STEP 3, starting from the entrance 4a of the starting shaft 4 by jacking, the downward gradient section 1b of the tunnel 1 that descends underground from the entrance 4a is constructed. The tunnel 1 is constructed using a tunneling machine capable of performing a hybrid jacking method that switches construction methods from the jacking method to the shield method, as described in the above-mentioned Patent Documents 1 and 2, for example.

[0022] Although not shown, the tunneling machine is adjusted so that the axis of the downward gradient portion 1b coincides with the axis of the cutter at the front end, and is supported by the support stand in the starting shaft 4. Any existing method may be used for the tunneling method. As the tunneling method, for example, the tunneling machine advances to excavate the tunnel, and an operator in the starting shaft 4 extends the tunnel body. This extension is performed by connecting a thrust pipe to the rear of the already assembled tunnel body. Then, the tunnel body connected to the thrust pipe is thrust forward using a thrust unit consisting of a thrust jack or the like to construct an underground pipe. At this time, the reaction force of the thrust unit is supported by the wall surface of the starting shaft 4.

[0023] In addition, the shorter the length L1 of the downward gradient portion 1b and the upward gradient portion 1c described later, the shorter the construction distance of the tunnel 1, so a steeper gradient is preferable from the viewpoint of shortening the construction period and reducing construction costs. However, although not shown, during the construction of the tunnel 1, a work cart is provided that runs on rails installed in the tunnel body and transports segments described later, and there is a limit to the gradient that this work cart can run on.

[0024] Therefore, it is necessary to determine the gradient of the downward gradient portion 1b and the upward gradient portion 1c taking both of these factors into consideration, and it is, for example, 10% to 45%, preferably about 30% (16.42°). When the gradient is 30%, if the depth A of the horizontal portion 1a of the tunnel 1 is 50m, the length L1 of the downward gradient portion 1b and the upward gradient portion 1c is about 180m, including the adjustment portion when transitioning from the gradient to the horizontal. The gradients of the downward gradient portion 1b and the upward gradient portion 1c may be different. Also, the gradient may change midway through the downward gradient portion 1b or the upward gradient portion 1c.

[0025] In the horizontal section construction step STEP 4, the jacking method is switched to the shield method to construct the horizontal section 1a that is connected to the deep part of the downward gradient section 1b. This switching of the construction method is preferably performed in the part on the upward gradient section 1c side from the boundary between the downward gradient section 1b and the horizontal section 1a. In addition, when the jacking pipe and the segment pipe have different diameters, an adapter pipe with a trapezoidal cross section disclosed in the above Patent Document 2 may be used.

[0026] The deepest part of the tunnel 1 and the uphill section 1c, which will be described later, are constructed by the shield method. This is because the jacking method adds jacking pipes from the starting shaft 4, making it difficult to handle curves where the direction changes midway through the tunnel, and when the tunnel is long, it is difficult to jack it up using only the jacks installed in the starting shaft 4. 。

[0027] The shield method may be any existing method. For example, the shield method involves a tunnel being excavated by a tunneling machine moving forward, and an underground pipe being constructed by a worker in the machine connecting a segment pipe made of assembled segments to the front part of the tunnel body and extending the tunnel body. The worker does not need to be present inside the machine all the time.

[0028] In STEP 5, the upward gradient portion construction process, starting from the back of the horizontal portion 1a, the shield method is used to construct the upward gradient portion 1c of the tunnel 1 up to the entrance 5a of the arrival shaft 5. The entire upward gradient portion 1c is constructed by the shield method.

[0029] This completes the construction of tunnel 1. When construction of tunnel 1 is complete, the excavator, work cart, and the like are removed from arrival shaft 5.

[0030] After that, in the gas pipe laying step STEP 6, referring to Fig. 3, the side of the starting shaft 4 opposite to the tunnel 1 is expanded to form a slope 11, and a slope 12 is installed on the ground so as to be continuous with the slope 11. Then, the gas pipe 13 is inserted into the tunnel 1 along the slope 12 and the upper surface of the slope 11, thereby laying the gas pipe 13 in the tunnel 1.

[0031] After the gas pipe 13 is laid, in a backfilling step STEP 7, facilities such as above-ground slopes are removed and the departure shaft 4 and arrival shaft 5 are backfilled. This completes the construction of the tunnel 1 with the gas pipe 13 laid therein.

[0032] As described above, the tunnel construction method according to this embodiment is a method for excavating the tunnel 1 in the order of the downward gradient portion 1b descending from near the ground, the horizontal portion 1a, and the upward gradient portion 1c ascending to near the ground when constructing the tunnel 1 downward while avoiding pile foundations 2 and the like on existing structures. Since the gradient portions 1b and 1c are provided, it is no longer necessary to make the depth B of the departure shaft 4 and the arrival shaft 5 as deep as the depth A of the deepest part of the tunnel as in the above-mentioned Patent Documents 1 and 2, and it is possible to shorten the construction period and significantly reduce the construction costs for constructing the departure shaft 4 and the arrival shaft 5, and it is possible to shorten the construction period and reduce the construction costs for the entire tunnel 1.

[0033] Furthermore, in the tunnel construction method according to this embodiment, the downward gradient section 1b of the tunnel 1 is excavated using the jacking method, and the horizontal section 1a and the upward gradient section 1c are excavated using the shield method. In particular, when excavating the downward gradient section 1b of a deep tunnel 1, there is a risk of groundwater seeping into the tunnel 1 near the excavator located at the deepest part of the tunnel excavation (the part where the water pressure and earth pressure are greatest). Also, if a work cart runs away in the downward gradient section 1b, it is dangerous for workers to be present below the downward gradient section 1b. In particular, the inside of the tunnel excavator is narrow, and if such a danger occurs, there is a possibility that the workers will not be able to evacuate.

[0034] Therefore, the downward gradient section 1b is constructed using a jacking method that does not require a worker to be constantly present inside the excavator at the tip, allowing the worker to work in a safe place such as inside the starting shaft 4 or on the ground. Since the horizontal section 1a and the upward gradient section 1c are constructed using a shield method, the worker is often present inside the excavator, but even if groundwater seeps into the tunnel 1, it takes time for the horizontal section 1a to fill with groundwater, so the worker can evacuate during that time. Even if the work cart runs off the downward gradient section 1b, the worker is at a position some distance away from the downward gradient section 1b, so it is possible to reduce the risk of collision with the work cart.

[0035] The present invention is not limited to the method of constructing tunnel 1 specifically described in the above-mentioned embodiment, and can be modified as appropriate within the scope of the claims.

[0036] For example, in the embodiment, the case where the starting shaft 4 and the arrival shaft 5 are provided has been described. However, this is not limited to this, and the starting shaft 4 or the arrival shaft 5 may not be provided. If the starting shaft 4 is not provided, a pit entrance will be formed in the ground, and the support base must be provided on the ground and a reaction wall must be formed. This pit entrance corresponds to one pit entrance of the present invention. If the arrival shaft 5 is not provided, a pit entrance will be formed in the ground, and the support base must be provided on the ground, and an excavator or the like will be taken out from this pit entrance via the support base. This pit entrance corresponds to the other pit entrance of the present invention. [Explanation of symbols]

[0037] 1...tunnel, 1a...horizontal section, 1b...downward sloping section, 1c...upward sloping section, 2...pile foundation of existing structure, 3...river, 4...starting shaft, 4a...entrance (one side entrance), 5...arriver pile, 5a...entrance (other side entrance), 11...slope, 12...slope, 13...gas pipe.

Claims

1. A tunnel construction method carried out using a tunneling machine capable of performing a hybrid jacking method that switches from a jacking method to a shield method, a descending gradient section construction process in which a descending gradient section of the tunnel is constructed by starting from one of the tunnel entrances using a jacking method and descending underground from the one of the tunnel entrances at a gradient of 10% to 45%; A horizontal section construction process in which, in a section on the upslope side of the boundary between the downward gradient section and the horizontal section, the jacking method is switched to the shield method to construct a horizontal section connected to a deep part of the downward gradient section; and an upward gradient portion construction step of starting from the back of the horizontal portion using a shield construction method and constructing an upward gradient portion of the tunnel to the other entrance.

2. 2. A method for constructing a tunnel according to claim 1, wherein said one portal is formed in a departure shaft and said other portal is formed in a arrival shaft.

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