Shaft and tunnel construction methods

Abstract

To provide a construction method of a start shaft and a tunnel that enables smooth opening of a mine entrance without having to cut through an earth retaining wall and that can control inflows of ground water and sediment into the shaft.SOLUTION: A start shaft 1 includes an outer cylinder 2 provided in the ground, an inner cylinder 3 interpolated inside the outer cylinder 2, and a start cylinder 4 interpolated inside the inner cylinder 3. The outer cylinder 2 is formed with a first start opening 21 in which an excavator M can pass through. The start cylinder 4 is formed with a second start opening 41 in which the excavator M can pass through at a position corresponding to the first start opening 21, and a water stopping entrance 42 is formed inside the second start opening 41. By moving the inner cylinder 3, the first start opening 21 is connected to the second start opening 41.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vertical shaft for a shield tunneling method or a jacking method, and a tunnel construction method using the same. [Background technology]

[0002] In shield tunneling and jacking tunneling, a vertical shaft is sometimes used to set up a tunneling machine at a predetermined height before digging. The vertical shaft is formed by excavating the ground while forming a retaining wall. A known method for forming a vertical shaft involves driving cylindrical members (steel pipes or the like) into the ground as a retaining wall while connecting them together, and excavating the ground inside the cylindrical members. When the tunneling machine is launched from this shaft (starting shaft) or when it reaches the shaft, a cut is made in the tubular member using gas cutting or other methods to form a tunnel entrance (a starting or arrival entrance through which the tunneling machine can pass). At this time, ground improvement work is sometimes carried out on the ground around the tunnel entrance using chemical injection or other methods to prevent groundwater and earth and sand from flowing into the shaft (leading to flooding or collapse of the tunnel entrance). However, the work required for ground improvement and ground cutting is time-consuming, hindering the shortening of construction time. In addition, it is necessary to secure a construction yard for the area where ground improvement work is to be carried out. For this reason, Patent Document 1 discloses a vertical shaft in which a gate steel plate is placed in close contact with the outside of an opening formed in a tubular member that constitutes a retaining wall, and the opening is opened by sliding the gate steel plate, allowing a tunneling machine to pass through. However, in the shaft of Patent Document 1, there is a risk that the steel gate plate installed on the ground side may deform when the tubular member is driven into the ground. If the steel gate plate deforms, it may become impossible to slide, and the opening may not be able to be opened. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-284939 Summary of the Invention [Problem to be solved by the invention]

[0004] From this perspective, the present invention aims to propose a shaft and tunnel construction method that allows for smooth opening of the shaft entrance without cutting the retaining wall and that makes it possible to prevent groundwater and soil from flowing into the shaft. [Means for solving the problem]

[0005] The shaft of the present invention, which solves the above problem, comprises an outer cylinder installed underground, an inner cylinder inserted inside the outer cylinder, and an entrance cylinder inserted inside the inner cylinder. In the shaft of the present invention, The inner cylinder is placed on a base fixed to the inner surface of the outer cylinder, A first entrance is formed in the outer cylinder, and a second entrance is formed in the entrance cylinder. A tunneling machine can pass through the first and second entrances, and the second entrance is formed at a position corresponding to the first entrance. A water-stopping entrance is formed inside the second entrance to prevent the inflow of groundwater and earth and sand. In the first shaft of the present invention, by moving the inner cylinder upward, the first tunnel entrance and the second tunnel entrance become connected, allowing the tunneling machine to pass through. In the second shaft of the present invention, a third tunnel entrance is formed in the inner cylinder. The third tunnel entrance is formed at a height position corresponding to the height position of the first tunnel entrance, and the tunneling machine can pass through. In the second shaft of the present invention, by rotating the inner cylinder in the circumferential direction, the first tunnel entrance, the second tunnel entrance, and the third tunnel entrance are connected, allowing the tunneling machine to pass through.

[0006] In addition, a tunnel construction method using a first vertical shaft includes the steps of installing the outer tube with the inner tube inserted into the ground, inserting the entrance tube inside the inner tube, placing the tunneling machine in the vertical shaft with a portion of it inserted into the water-stopping entrance, pulling up the inner tube to connect the first tunnel entrance and the second tunnel entrance, and launching the tunneling machine from the first tunnel entrance and the second tunnel entrance to construct a tunnel. Furthermore, the tunnel construction method using the second shaft comprises the steps of installing the outer tube with the inner tube inserted into the ground, inserting the entrance tube inside the inner tube, placing the tunneling machine in the shaft with a portion of it inserted into the water-stopping entrance, rotating the inner tube circumferentially to connect the first tunnel entrance, the second tunnel entrance, and the third tunnel entrance, and launching the tunneling machine from the first tunnel entrance, the second tunnel entrance, and the third tunnel entrance to construct a tunnel.

[0007] These shafts (first shaft, second shaft) and tunnel construction methods do not require face-cutting, which reduces the labor and costs of face-cutting work and the associated ground improvement work. Furthermore, during shaft construction, earth pressure acts primarily on the outer cylinder, so no harmful deformation occurs to the inner cylinder inserted into the outer cylinder. This makes it easier to move the inner cylinder, allowing for smooth opening of the tunnel entrance. In addition, water-stopping properties can be improved by providing a water-stopping material that seals the gap between the outer cylinder and the inner cylinder along the periphery of the first well entrance of the outer cylinder. In addition, water-stopping properties can be further improved by providing water-stopping materials on the outer surface of the inner tube above and below the first well entrance to seal the gap between the outer tube and the inner tube. [Effects of the Invention]

[0008] According to the shaft and tunnel construction method of the present invention, the shaft entrance can be opened smoothly without the need for mirror cutting, and it is possible to prevent groundwater and earth and sand from flowing into the shaft. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams showing an outline of a vertical shaft according to an embodiment of the present invention, in which (a) is a front view and (b) is a cross-sectional view. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing a portion of the vertical shaft of the first embodiment. [Figure 3] 1 is a flowchart showing the steps of a tunnel construction method according to an embodiment of the present invention. [Figure 4] (a) and (b) are cross-sectional views showing the retaining wall formation process. [Figure 5] FIG. 2 is a perspective view showing a part of an outer cylinder and an inner cylinder. [Figure 6] 10A and 10B are cross-sectional views showing the step of inserting the starting cylinder, in which FIG. 10A shows the stage being formed, FIG. 10B shows the stage being inserted into the starting cylinder, and FIG. 10C shows the stage after insertion into the starting cylinder. [Figure 7] 10(a) and 10(b) are perspective views showing the formation of a watertight entrance. [Figure 8] 10(a) and 10(b) are perspective views showing the tunneling machine installation process. [Figure 9] FIG. 10 is a perspective view showing a starting port connecting step of the first embodiment. [Figure 10] 1(a) and 1(b) are perspective views showing an excavation step of the first embodiment. [Figure 11] FIG. 10 is an enlarged cross-sectional view showing a part of the vertical shaft of the second embodiment. [Figure 12] 10(a) and 10(b) are schematic diagrams showing a starting port connecting step of the second embodiment. [Figure 13] FIG. 10 is a perspective view showing an excavation step of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment In this embodiment, a case will be described in which a tunnel is constructed by starting a tunneling machine M from a starting shaft (vertical shaft) 1 having a cylindrical earth retaining wall 11. The starting shaft 1 is shown in FIG. 1(a) and 1(b), the starting shaft 1 of this embodiment comprises an outer cylinder 2 (retaining wall 11) installed underground, an inner cylinder 3 inserted inside the outer cylinder 2, and a starting shaft (entrance cylinder) 4 inserted inside the inner cylinder 3. A starting entrance (pit entrance) 10 is formed in the starting shaft 1 according to the tunnel excavation direction (starting direction). The outer cylinder 2 is formed by connecting multiple steel pipes 20, which are circular in plan view, in the vertical direction, and constitutes the retaining wall 11 of the departure shaft 1. The outer cylinder 2 is formed to reach a position lower than the height of the tunnel. The outer cylinder 2 is formed with a first departure opening (first tunnel entrance) 21 (departure opening 10), which is circular in front view and has a diameter that allows the tunneling machine M to pass through, corresponding to the height and departure direction of the tunnel. Figure 2 shows an enlarged cross-sectional view of the departure shaft 1. As shown in Figure 2, a first departure opening waterstop material 51 is fixed to the inner surface of the outer cylinder 2 along the periphery of the first departure opening 21. The first departure opening waterstop material 51 is made of a ring-shaped resin member and has a thickness that seals the gap between the outer cylinder 2 and the inner cylinder 3. Although not shown in the figure, in this embodiment, the first departure opening 21 (departure opening 10) is reinforced. The first launch opening 21 may be reinforced, for example, by welding reinforcing bars along the periphery of the first launch opening 21 or by welding steel pipes to the inside and outside of the first launch opening 21.

[0011] The inner cylinder 3 is made of a steel pipe that is circular in plan view and has an outer diameter smaller than the inner diameter of the steel pipe 20 that constitutes the outer cylinder 2. The inner cylinder 3 also has an inner diameter that corresponds to the bucket (excavation means) used to excavate the shaft. As shown in Figure 2, the inner cylinder 3 has a length (vertical height) that is the diameter of the first opening 21 plus a margin, and is provided at a height position corresponding to the first opening 21 so as to shield the first opening 21. The margin is a length that ensures an overlap between the outer cylinder 2 and the inner cylinder 3 to ensure watertightness. On the outer surface of the inner cylinder 3, inner cylinder water sealing materials 52, 52 are provided above and below the first opening 21. The inner cylinder water sealing material 52 is made of a resin member that is annular in plan view and has a thickness equal to or greater than the gap between the outer cylinder 2 and the inner cylinder 3, and seals the gap between the outer cylinder 2 and the inner cylinder 3. The inner diameter of the inner cylinder water sealing material 52 is equal to or less than the outer diameter of the inner cylinder 3, and the outer diameter of the inner cylinder water sealing material 52 is equal to or greater than the inner diameter of the outer cylinder 2. In this embodiment, a caulking agent 53 made of resin or the like is used to perform a waterproofing treatment between the periphery of the first opening 21 and the outer surface of the inner cylinder 3.

[0012] The inner cylinder 3 is placed on a pedestal 6 fixed to the inner surface of the outer cylinder 2. The pedestal 6 is formed by welding or bolting a steel plate having an annular shape in plan view to the inner surface of the outer cylinder 2 at a position higher than the bottom slab 12 of the departure shaft 1. In this embodiment, a water-stopping material is interposed between the lower end surface of the inner cylinder 3 and the pedestal 6. Furthermore, a hanging fitting 31 is fixed to the upper part of the inner cylinder 3, and is configured so that a lifting member (such as a wire) suspended from a crane or the like can be engaged. The inner cylinder 3 can be lifted by a crane or the like, and its lower end can be raised to a position higher than the first opening 21 (a height position at which the first opening 21 can be opened).

[0013] The launch tube 4 is made of a steel pipe that is circular in plan view and has an outer diameter smaller than the inner diameter of the steel pipe that constitutes the inner tube 3. As shown in FIG. 2, the launch tube 4 is formed with a second launch port (second tunnel entrance) 41, through which the tunneling machine M can pass, at a position corresponding to the first launch port 21. The center of the second launch port 41 is located on an extension of the central axis of the tunneling machine M when it is launched. The inner diameter of the second launch port 41 is equal to or greater than the inner diameter of the first launch port 21. The length (vertical dimension) of the launch tube 4 is set to a length that ensures an overlap between the inner tube 3 and the launch tube 4 to maintain watertightness even when the inner tube 3 is raised and the lower end of the inner tube 3 is positioned above the second launch port 41. Although not shown in the figure, it is desirable to reinforce the second launch port 41. The second launch opening 41 may be reinforced, for example, by welding reinforcing bars along the periphery of the second launch opening 41 or by welding steel pipes to the inside and outside of the second launch opening 41.

[0014] A second launch port water stop material 54 is fixed to the outer surface of the launch tube 4 along the periphery of the second launch port 41. The second launch port water stop material 54 is made of a ring-shaped resin member and has a thickness that seals the gap between the inner tube 3 and the launch tube 4. In addition, a launch tube water stop material 55 that seals the gap between the inner tube 3 and the launch tube 4 is provided on the upper outer surface of the launch tube 4. The launch tube water stop material 55 is made of a ring-shaped resin member in a plan view that has a thickness that is equal to or greater than the gap between the inner tube 3 and the launch tube 4. The inner diameter of the launch tube water stop material 55 is equal to or smaller than the outer diameter of the launch tube 4, and the outer diameter of the launch tube water stop material 55 is equal to or larger than the inner diameter of the inner tube 3. A water-stopping entrance 42 is formed on the inner surface of the launch tube 4. The water-stopping entrance 42 is located inside the second launch port 41 and shields the gap formed between the second launch port 41 and the tunneling machine M to prevent soil and sand from flowing into the launch shaft 1. In this embodiment, the water-stopping entrance 42 is formed by fixing an entrance metal fitting to the launch tube 4. The water-stopping entrance 42 is provided with two stages of water-stopping means 43 along the direction of travel of the tunneling machine M to shield the gap between the water-stopping entrance 42 and the tunneling machine M. In this embodiment, a water-stopping brush is used as the water-stopping means 43, but the configuration of the water-stopping means is not limited thereto and may be, for example, a rubber gasket. Furthermore, the number of stages of the water-stopping means 43 is not limited to two and may be, for example, one stage or three or more stages.

[0015] The lower end of the launch cylinder 4 is fixed to a mount 7 fixed to the outer cylinder 2. The mount 7 is made of a ring-shaped plate material, and its outer periphery is welded all around to the inner surface of the outer cylinder 2. The lower end of the launch cylinder 4 is also welded all around to the mount 7. This seals the gap between the outer cylinder 2 and the launch cylinder 4 at the lower end of the launch cylinder 4. Note that the launch cylinder 4 does not necessarily have to be welded all around to the mount 7; for example, it may be placed on the mount 7 with a waterproof material interposed between the lower end of the launch cylinder 4 and the mount 7, and bolted to prevent biased movement. In this embodiment, a reinforcing diagonal member 71 is provided between the underside of the mount 7 and the inner surface of the outer cylinder 2. The diagonal member 71 may be provided as needed. The upper end of the launch cylinder 4 is fixed to the outer cylinder 2 via a fixing member 8. The fixing member 8 is made of a rod-shaped or plate-shaped member, and the upper end of the fixing member 8 is fixed to the inner surface of the outer cylinder 2, while the lower end of the fixing member 8 is fixed to the upper end of the launch cylinder 4. The length of the fixing member 8 is determined so that the distance from the height position of the joint between the upper end of the fixing member 8 and the outer cylinder 2 to the height position of the upper end of the second launch opening 41 is equal to or greater than the length (height) of the inner cylinder 3. Therefore, fixing the upper end of the launch cylinder 4 to the outer cylinder 2 does not hinder the rise of the inner cylinder 3. The fixing member 8 may be made of, for example, a steel rod. In this embodiment, a mounting bracket 81 protrudes from the inner surface of the outer cylinder 2, and the upper end of the fixing member 8 is fixed to this mounting bracket 81.

[0016] The tunnel construction method using the starting shaft 1 of this embodiment will be described below. The steps of the tunnel construction method are shown in Figure 3. As shown in Figure 3, the tunnel construction method of this embodiment includes a retaining wall formation process S1, a starting tube insertion process S2, a tunneling machine installation process S3, a starting port connection process S4, and an excavation process S5. The earth-retaining wall formation step S1 is a step of forming an earth-retaining wall 11 (outer cylinder 2) underground. Figure 4 shows the earth-retaining wall formation step S1. As shown in Figures 4(a) and (b), the earth-retaining wall 11 is constructed by placing (casting or pressing) steel pipes 20 into the ground and excavating the ground within the steel pipes 20. After the steel pipes 20 are connected to form the earth-retaining wall 11 (outer cylinder 2) extending from the ground surface GL to a predetermined depth, concrete is poured at the bottom to form the base slab 12 (see Figure 2). FIG. 5 shows a portion of the outer cylinder 2 (retaining wall 11) and the inner cylinder 3. As shown in FIG. 5, a first opening 21 is formed in a portion of the steel pipe 20 that constitutes the outer cylinder 2. When the steel pipe 20 with the first opening 21 formed therein is driven into the ground, the inner cylinder 3 is inserted into the steel pipe 20 to shield the first opening 21. This prevents soil, sand, groundwater, and the like from entering through the first opening 21. The outer cylinder 2 is positioned so that the center of the first opening 21 coincides with the central axis of the excavator M when it starts. Note that in the retaining wall formation step S1, the bucket and the inner cylinder 3 are prevented from interfering with each other during excavation. One method for preventing interference between the bucket and the inner cylinder 3 is, for example, to install wedge-shaped members (guide rails) at appropriate intervals in the step between the outer cylinder 2 and the inner cylinder 3 to guide the bucket so that it is positioned approximately at the center of the inner cylinder 3 (not shown).

[0017] The starting cylinder insertion step S2 is a step of inserting the starting cylinder 4 inside the inner cylinder 3. Figure 6 shows the starting cylinder insertion step S2. First, as shown in Figure 6(a), a mount 7 is formed on the inner surface of the outer cylinder 2. The mount 7 is formed by welding a ring-shaped steel plate to the inner surface of the outer cylinder 2 all around. At this time, the mount 7 is reinforced with diagonal members 71 as necessary. Next, as shown in FIG. 6(b), the launch tube 4 is lowered from above the outer tube 2 (retaining wall 11) to insert the launch tube 4 into the inner tube 3. The launch tube 4 is fixed to the outer tube 2 with the second launch opening 41 aligned with the first launch opening 21, as shown in FIG. 2. That is, the launch tube 4 is positioned so that the center of the second launch opening 41 coincides with the central axis of the excavator M when it is launched. Then, as shown in FIG. 6(c), the launch tube 4 is placed on the pedestal 7, and the lower end of the launch tube 4 is welded to the pedestal 7 all around. The upper end of the launch tube 4 is fixed to the outer tube 2 using the fixing member 8. Note that the launch tube 4 does not necessarily have to be welded to the pedestal 7. For example, if the launch tube is placed on the pedestal 7 via a waterproofing material such as an O-ring, the launch tube 4 may be fixed using bolts without welding.

[0018] The tunneling machine installation step S3 is a step of installing the tunneling machine M in the starting shaft 1. First, as shown in Fig. 7, a watertight entrance 42 is formed in the starting barrel 4. Fig. 7 is a perspective view showing the starting shaft 1. The watertight entrance 42 is formed by fixing an entrance metal fitting to the inner surface of the starting barrel 4, inside the second starting port 41. The starting cylinder 4 may be inserted into the inner cylinder 3 with the water blocking entrance 42 formed in advance. Next, the tunneling machine M is hung from above the starting shaft 1 and inserted into the starting shaft 1. Figure 8 shows the installation of the tunneling machine M. As shown in Figure 8(a), the tunneling machine M is lowered to a predetermined height, and then, as shown in Figure 8(b), the tip (part) of the tunneling machine M is inserted into the water-stopping entrance 42. Once the tunneling machine M has been installed, the inside of the water-stopping entrance 42 is filled with mud-adding material. Note that Figure 8 does not show the machine support base, reaction force receiving material, main push jack, etc.

[0019] The launch port connecting step S4 is a step of connecting the first launch port 21 and the second launch port 41. FIG. 9 shows the launch port connecting step S4. The first launch port 21 and the second launch port 41 are connected by lifting the inner tube 3 and moving it upward, as shown in FIG. 9. The inner tube 3 is lifted by winding up a wire extended from a crane or the like while the wire is engaged with a hoisting fixture 31 (see FIG. 2). Note that the method of lifting the inner tube 3 is not limited to lifting with a wire; for example, a hydraulic jack, a chain block, or a rack and pinion may also be used. The inner tube 3 is lifted until its lower end is positioned above the upper ends of the first launch port 21 and the second launch port 41. The excavation step S5 is a step of constructing a tunnel. Figure 10 shows the starting state of the tunneling machine M. As shown in Figure 10, the tunnel is constructed by starting the tunneling machine M from the first starting port 21 and the second starting port 41 and placing segments or jacking pipes, etc., in a borehole formed in the ground.

[0020] According to the departure shaft (shaft) 1 of this embodiment and the tunnel construction method using this departure shaft (shaft) 1, the departure opening 10 (first departure opening 21 and second departure opening 41) is formed in advance in the retaining wall 11, eliminating the need for face-cutting, thereby reducing the effort and cost of face-cutting work and the ground improvement associated with face-cutting. The departure openings 10 (first departure opening 21 and second departure opening 41) can be opened simply by raising the inner cylinder 3, resulting in excellent workability. Furthermore, when constructing the departure shaft 1, earth pressure and the like act mainly on the outer cylinder 2, so no harmful deformation occurs in the inner cylinder 3. This makes it easy to move the inner cylinder 3, and allows the first departure opening 21 and the second departure opening 41 to be opened smoothly.

[0021] Since a water-stopping material 51 for the first launch port, a water-stopping material 52 for the inner tube, a caulking agent 53, a water-stopping material 54 for the second launch port, and a water-stopping material 55 for the launch tube are provided, soil and groundwater do not flow into the launch shaft 1 through the gap between the outer tube 2 and the inner tube 3 or the gap between the inner tube 3 and the launch tube 4. The launch cylinder 4 is fixed integrally to the outer cylinder 2 at the top and bottom, and therefore does not move (shift) in the vertical or circumferential direction when launching the tunneling machine M. Furthermore, the launch cylinder 4 is fixed to the outer cylinder 2 at a position higher than the movement range of the inner cylinder 3 by a rod-shaped or plate-shaped fixing member 8, and therefore the movement of the inner cylinder 3 is not impeded. The gap between the outer cylinder 2 and the launch cylinder 4 is sealed by the mount 7, improving waterproofing.

[0022] Second Embodiment In the second embodiment, as in the first embodiment, a case will be described in which a tunneling machine M is started from a starting shaft (vertical shaft) 1 having a cylindrical earth retaining wall 11 to construct a tunnel. The departure shaft 1 of this embodiment comprises an outer tube 2 (retaining wall 11) installed underground, an inner tube 3 inserted inside the outer tube 2, and a departure tube (entrance tube) 4 inserted inside the inner tube 3 (see Figure 1). The details of the outer cylinder 2 are the same as those shown in the first embodiment, and therefore a detailed description thereof will be omitted.

[0023] The inner cylinder 3 is made of a circular steel pipe in plan view, with an outer diameter smaller than the inner diameter of the steel pipe constituting the outer cylinder 2. The inner cylinder 3 has an inner diameter corresponding to the bucket (excavation means) used to excavate the shaft. Figure 11 shows a partial enlarged view of the starting shaft 1. As shown in Figure 11, the inner cylinder 3 has a length (vertical height) equal to the diameter of the first starting opening (first tunnel entrance) 21 plus a clearance margin. The clearance margin is set to a length sufficient to ensure watertightness between the outer cylinder 2 and the inner cylinder 3. The inner cylinder 3 also has a third opening (third tunnel entrance) 32 formed at a height corresponding to the height of the first opening 21, through which the tunneling machine M can pass. The inner diameter of the third opening 32 is equal to or greater than the inner diameter of the first opening 21. The inner cylinder 3 is inserted into the outer cylinder 2 with the center of the third opening 32 laterally offset from the center of the first opening 21 by at least the inner diameter of the third opening 32 so that the third opening 32 does not overlap with the first opening 21. That is, the first opening 21 is shielded by the outer surface (plate surface) of the inner cylinder 3. Although not shown in the drawings, it is desirable to reinforce the third opening 32. The third opening 32 can be reinforced, for example, by welding reinforcing bars along the periphery of the third opening 32 or by welding steel pipes to the inside and outside of the third opening 32. On the outer surface of the inner tube 3, inner tube waterstop materials 52, 52 are provided above and below the first opening 21. The inner tube waterstop material 52 is made of a resin member that is annular in plan view and has a thickness equal to or greater than the gap between the outer tube 2 and the inner tube 3, sealing the gap between the outer tube 2 and the inner tube 3. The inner diameter of the inner tube waterstop material 52 is equal to or less than the outer diameter of the inner tube 3, and the outer diameter of the inner tube waterstop material 52 is equal to or greater than the inner diameter of the outer tube 2. In addition, a third opening waterstop material 56 is fixed to the outer surface of the inner tube 3 along the periphery of the third opening 32. The third opening waterstop material 56 is made of a resin annular member and has a thickness that seals the gap between the outer tube 2 and the inner tube 3. Furthermore, a caulking agent 53 made of resin or the like is used to waterproof the area between the periphery of the first opening 21 and the inner surface (plate surface) of the inner tube 3.

[0024] The inner cylinder 3 is placed on a pedestal 6 fixed to the inner surface of the outer cylinder 2. The pedestal 6 is formed by welding or bolting an annular steel plate to the inner surface of the outer cylinder 2 at a position higher than the bottom slab 12 of the departure shaft 1. In this embodiment, a running means 33 such as a roller, wheel, or ball is interposed between the lower end of the inner cylinder 3 and the pedestal 6, allowing the inner cylinder 3 to rotate smoothly on the pedestal 6. A rack 34 is provided on the upper part of the inner cylinder 3. The rack 34 is engaged with a pinion (not shown) attached to the output shaft of the motor. The inner cylinder 3 rotates in the circumferential direction on the base 6 by operating the motor.

[0025] The launch tube 4 is made of a steel pipe that is circular in plan view and has an outer diameter smaller than the inner diameter of the steel pipe that makes up the inner tube 3. The launch tube 4 is formed with a second launch port (second tunnel entrance) 41, through which the tunneling machine M can pass, at a position corresponding to the first launch port 21. The center of the second launch port 41 is located on an extension of the central axis of the tunneling machine M when launching. The inner diameter of the second launch port 41 is equal to or greater than the inner diameter of the first launch port 21. In addition, the length (vertical dimension) of the launch tube 4 is set to a dimension that ensures sufficient length above and below the second launch port 41, so as to ensure an overlap between the inner tube 3 and the launch tube 4 that can maintain watertightness. The lower end of the launch cylinder 4 is fixed to a mount 7 fixed to the outer cylinder 2. The mount 7 is made of an annular plate material, and the outer periphery is welded all around to the inner surface of the outer cylinder 2. The lower end of the launch cylinder 4 is also welded all around to the mount 7. In this way, the gap between the outer cylinder 2 and the launch cylinder 4 at the lower end of the launch cylinder 4 is sealed. Note that if waterproofing is ensured by placing the launch cylinder 4 on the mount 7 via a waterproofing material, the all around welding of the lower end of the launch cylinder 4 may be omitted. In this embodiment, a reinforcing diagonal member 71 is provided between the underside of the mount 7 and the inner surface of the outer cylinder 2. The diagonal member 71 may be provided as needed.

[0026] The upper end of the launch cylinder 4 is fixed to the outer cylinder 2 via a fixing member 8. The fixing member 8 is made of a rod-shaped or plate-shaped member. The upper end of the fixing member 8 is fixed to the inner surface of the outer cylinder 2, and the lower end of the fixing member 8 is fixed to the upper end of the launch cylinder 4. The fixing member 8 may be made of, for example, a steel rod. In this embodiment, a mounting bracket 81 is provided to protrude from the inner surface of the outer cylinder 2, and the upper end of the fixing member 8 is fixed to this mounting bracket 81. On the outer surface of the launch tube 4, a second launch port water stop material 54 and a launch tube water stop material are provided, similar to the launch tube 4 of the first embodiment. Furthermore, similar to the launch tube 4 of the first embodiment, a water blocking entrance 42 is formed on the inner surface of the launch tube 4 at a position inside the second launch port 41. The configuration of the water blocking entrance 42 is not limited, but in this embodiment, it is the same as the water blocking entrance 42 of the first embodiment.

[0027] The tunnel construction method using the starting shaft 1 of this embodiment will be described below. The tunnel construction method of this embodiment comprises a retaining wall formation process S1, a starting tube insertion process S2, a tunneling machine installation process S3, a starting port connection process S4, and an excavation process S5 (see FIG. 3). The details of the retaining wall formation process S1, the starting tube insertion process S2, and the tunneling machine installation process S3 are the same as those shown in the first embodiment, so detailed explanations will be omitted.

[0028] The launch port connecting step S4 is a step of connecting the first launch port 21, the second launch port 41, and the third launch port 32. Figure 12 shows the launch port connecting step S4. Note that the launch tube 4 is not shown in Figure 12. The first launch port 21, the second launch port 41 (see Figure 11), and the third launch port 32 are connected by rotating the inner tube 3 in the circumferential direction, as shown in Figures 12(a) and 12(b). The inner tube 3 is rotated in the circumferential direction by operating the motor with the motor gear meshed with the rack 34. The inner tube 3 is rotated until the center of the third launch port 32 reaches a position that coincides with an extension of the central axis of the tunneling machine M in the excavation direction. The excavation process S5 is a process of constructing a tunnel. Figure 13 shows the starting state of the tunneling machine M. As shown in Figure 13, the tunneling machine M starts by passing through first starting port 21, second starting port 41, and third starting port 32. Then, the tunnel is constructed by placing segments or a jacking pipe in a borehole formed in the ground.

[0029] According to the departure shaft 1 and tunnel construction method using this departure shaft 1 of this embodiment, the departure openings 10 (first departure opening 21, second departure opening 41, and third departure opening 32) are formed in advance in the retaining wall 11, eliminating the need for face-cutting, thereby reducing the effort and cost of face-cutting work and ground improvement associated with face-cutting. The departure openings 10 (first departure opening 21, second departure opening 41, and third departure opening 32) are opened simply by rotating the inner cylinder 3 circumferentially, resulting in excellent workability. The effects of employing the departure shaft 1 and tunnel construction method of this second embodiment are similar to those of the departure shaft 1 and tunnel construction method of the first embodiment, so detailed explanations will be omitted.

[0030] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-described components can be appropriately modified within the scope of the present invention. In the above embodiment, the shaft of the present invention is described as being used as a departure shaft, but the shaft of the present invention may also be used as a arrival shaft. The first launch port water stop material 51, the inner tube water stop material 52, the second launch port water stop material 54, the launch tube water stop material 55, and the third launch port water stop material 56 are not limited to being annular, but may be, for example, U-shaped. The installation location, material, shape, etc. of the water stop material may be determined appropriately. The base (base 6 in the first embodiment) on which the inner cylinder 3 is placed does not necessarily have to be an annular plate material. For example, it may be an inverted L-shaped steel material. In this case, a plurality of bases 6 are provided at predetermined intervals (intermittently) in the circumferential direction of the outer cylinder 2. When rotating the inner cylinder 3 in the circumferential direction to open the starting port 10, the method of rotating the inner cylinder 3 is not limited to a method using a motor, and may be performed by a wire system or a push rod system, for example. Also, the inner cylinder 3 does not necessarily need to have a traveling means, and the traveling means 33 may be provided as needed. The material constituting the fixing member 8 is not limited to steel rods, and may be, for example, steel materials such as steel plates or angle bars. In addition, the steel rods constituting the fixing member 8 are not limited, and for example, round steel, square steel, deformed steel bars, etc. may be used. [Explanation of symbols]

[0031] 1 Departure shaft (shaft) 10 Departure 11 Earth retaining wall 12 bottom plate 2 outer cylinder 20 Steel pipe 21 First starting point (First mine entrance) 3 Inner cylinder 31 Hanging hardware 32 Third starting point (third mine entrance) 33 Transportation 4. Launch tube (entrance tube) 41 Second starting gate (second well mouth) 42 Water-stop entrance 51 Water-stopping material for first launch gate 52 Water-stopping material for inner tube 53 Caulking agent 54 Water-stopping material for second launch gate 55 Water-stopping material for launch tubes 56 Water-stopping material for third launch gate 6. Pedestal 7 Mounting stand 71 Diagonal 8 Fixing member 81 Mounting bracket G Ground M tunneling machine

Claims

1. an outer cylinder installed underground; an inner cylinder inserted inside the outer cylinder; An entrance tube inserted inside the inner tube, The inner cylinder is placed on a base fixed to the inner surface of the outer cylinder, The outer cylinder has a first tunnel entrance formed therein through which a tunneling machine can pass, The entrance tube has a second tunnel entrance formed at a position corresponding to the first tunnel entrance through which the tunneling machine can pass, and a water-stopping entrance formed inside the second tunnel entrance, A vertical shaft characterized in that the first shaft entrance and the second shaft entrance are communicated by moving the inner cylinder upward.

2. an outer cylinder installed underground; an inner cylinder inserted inside the outer cylinder; An entrance tube inserted inside the inner tube, The inner cylinder is placed on a base fixed to the inner surface of the outer cylinder, The outer cylinder has a first tunnel entrance formed therein through which a tunneling machine can pass, The entrance tube has a second tunnel entrance formed at a position corresponding to the first tunnel entrance through which the tunneling machine can pass, and a water-stopping entrance formed inside the second tunnel entrance, The inner cylinder has a third tunnel entrance formed at a height position corresponding to the height position of the first tunnel entrance, through which the tunneling machine can pass, A vertical shaft characterized in that the first shaft entrance, the second shaft entrance, and the third shaft entrance are connected to each other by rotating the inner cylinder in a circumferential direction.

3. A vertical shaft as described in claim 1 or claim 2, characterized in that the outer tube is provided with a water-stopping material along the periphery of the first tunnel entrance to seal the gap between the outer tube and the inner tube.

4. A vertical shaft as described in any one of claims 1 to 3, characterized in that a water-stopping material is provided on the outer surface of the inner tube above and below the first tunnel entrance to seal the gap between the outer tube and the inner tube.

5. A tunnel construction method using the shaft according to claim 1, a step of placing the outer cylinder with the inner cylinder inserted into the ground; inserting the entrance tube into the inner tube; a step of disposing the tunneling machine in the vertical shaft with a portion of the tunneling machine inserted into the watertight entrance; A step of lifting the inner cylinder to connect the first well opening and the second well opening; a step of launching the tunnel boring machine from the first tunnel entrance and the second tunnel entrance to construct a tunnel.

6. A tunnel construction method using the shaft according to claim 2, a step of placing the outer cylinder with the inner cylinder inserted into the ground; inserting the entrance tube into the inner tube; a step of disposing the tunneling machine in the vertical shaft with a portion of the tunneling machine inserted into the watertight entrance; rotating the inner cylinder in a circumferential direction to connect the first well mouth, the second well mouth, and the third well mouth; a step of launching the tunnel boring machine from the first tunnel entrance, the second tunnel entrance, and the third tunnel entrance to construct a tunnel.

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