JP2005171549A - Tunnel construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently perform a series of steps ranging from excavating to lining by streamlining, particularly, the installation of an invert part in constructing a tunnel. <P>SOLUTION: While the tunnel 100 is excavated by a full face tunnel boring machine, excavated waste is scraped off to the bottom part of the tunnel at the rear thereof to form a construction rock 108, and concrete is sprayed and lock bolts are driven in the side and top wall surfaces of the tunnel. A movable scaffold board 111 is installed at the rear thereof and the installation rock is excavated in that span to form a lining concrete 115 on the invert part. Also, at the rear thereof, excavated waste is scraped off onto the coating concrete of the invert part to form a road floor 118, and the coating concrete is formed against the side and top parts of the tunnel by a movable arch center. A pilot pit is excavated prior to the tunnel and the surroundings thereof are improved for sealing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tunnel construction method, and more particularly to a rational tunnel construction method for efficiently constructing a tunnel by a full-section excavation method using a tunnel boring machine.

  When a tunnel is constructed by a full-section excavation method using a tunnel boring machine (TBM) or a shield excavator, the excavation cross section is usually circular. However, it is not always easy to efficiently construct the inverted part because the travel of heavy machinery in the mine must be limited.

For this reason, various proposals have been made regarding the construction of the invert part. For example, Patent Document 1 discloses a method of placing concrete in an invert part using an invert form, and Patent Document 2 discloses a tunnel using a moving work floor. There is disclosure about the construction method of Invert.
JP 2001-173386 A JP 2003-8295 A

  The construction methods disclosed in Patent Documents 1 and 2 are examples of application to a tunnel with a horseshoe-shaped cross section, but when applying such a construction method to a tunnel with a circular cross section, a large amount of concrete is placed at the bottom of the tunnel. A roadbed must be formed, especially when constructing large sections and long-distance tunnels, which requires a lot of labor and cost for the long-distance transportation and disposal of a large amount of excavation generated by full-section excavation. In addition, the construction of such an invert portion requires a lot of labor and cost, and an effective improvement measure in this respect has been desired.

  In view of the above circumstances, the present invention aims to rationalize the construction of the invert part and to provide a rational tunnel construction method capable of efficiently performing not only the construction of the invert part but also a series of steps from excavation to lining. It is an object.

  In the tunnel construction method of the present invention, a tunnel is excavated by a full-section tunnel excavator, and a part of excavation sludge discharged from the full-section tunnel excavator is sprinkled to the bottom of the tunnel at the rear to form a construction panel. At the same time, spray concrete on the side and top walls of the tunnel and place rock bolts, and install a movable jetty behind which heavy equipment can run, and within the span of the movable jetty. Excavating the board to form lining concrete in the invert part, and behind that, on the lining concrete of the invert part, excavation slip from the full-section tunnel excavator or excavation slip from the construction board or those Both sides of the tunnel are squeezed out to form a roadbed and covered with mobile centles against the side and top of the tunnel. It is intended to form the concrete.

  When the tunnel construction method of the present invention is applied to a springy ground, prior to excavation of the tunnel by a full-section tunnel excavator, a pilot pit with a smaller diameter is pre-excavated and covered with segments. By working from the inside of the pilot mine, the ground outside the excavation cross section of the tunnel to be built is stopped and improved, and then the pilot pit segment is dismantled and removed, and the whole ground around the pilot mine is cut. It is preferable to excavate with a tunnel excavator.

  According to the present invention, a part of excavation sludge is first backfilled in the invert part to form a temporary construction board, and by providing a movable jetty on the construction board, various heavy machines can be placed on the construction board and It is possible to run freely on the mobile jetty and perform various operations efficiently. Also, after excavating the construction board below the mobile jetty to form the lining concrete on the invert part, the excavation gap is backfilled to form the roadbed, thereby making the excavation gap effective as a backfill material Therefore, it is possible to reduce the amount of discharge and not to place a large amount of concrete in order to form a roadbed as in the conventional case, so that the construction of the invert portion can be rationalized sufficiently. Further, by performing the primary lining with sprayed concrete and rock bolts, it is advantageous in terms of cost compared to the primary lining by the segment, and the secondary lining can be efficiently constructed by moving centles.

  Prior to the tunnel excavation, the pilot mine is excavated in advance and the water is improved around it. It is possible to build.

  One embodiment of the tunnel construction method of the present invention will be described with reference to FIGS. In the tunnel construction method of the present embodiment, when constructing a main tunnel 100 on a springy ground, first, a pilot mine 101 having a smaller diameter than that of the tunnel 100 is first excavated to segment (not shown in FIG. 1). ) To improve the water stop of the ground outside the planned section of tunnel 100 by working from the inside of the pilot mine 101, and then expand the pilot mine 101 while dismantling and removing the segments. (Reaming) is basically to form a tunnel 100 by excavating the surroundings, and FIGS. 1 to 3 show each of the pilot pits 101 after excavation by the full-section tunnel excavator 102. The steps are shown in the order of steps.

  In this embodiment, a tunnel boring machine (TBM) configured to excavate the circumference of the pilot pit 101 so as to expand the diameter of the pilot pit 101 by the annular cutter 103 provided at the foremost part is adopted as the full-section tunnel excavator 102. doing. As shown in FIG. 1, a rock bolt driving machine 104 and a concrete spraying machine 105 are mounted on the full-section tunnel excavator 102, and concrete is sprayed on the side and top of the inner surface of the tunnel immediately after excavation. A primary lining is formed by driving a lock bolt.

  On the rear side, the excavation gap discharged from the tunnel excavator 102 is transported by the continuous loader and the dump truck 107, the excavation gap is spun off to the bottom of the tunnel, the invert part is temporarily backfilled, and the temporary construction board 108 so that heavy equipment such as a dump truck 107 and jumbo 109 can freely travel on the construction panel 108, and the width is secured so that the heavy equipment can pass each other as shown in FIG. 1 (b). To do.

  On the rear side, concrete blasting and rock bolting are performed on the side and top of the tunnel inner surface by the self-propelled spraying robot 110 and jumbo 109 to form a primary lining.

  On the rear side, as shown in FIG. 2, a movable jetty 111 that can move in the tunnel axial direction is installed, and the invert part below the heavy equipment is installed while passing each heavy machine on the movable jetty 111. Do. That is, in the span of the mobile pier 111, from the pit side to the face side, the construction panel 108 is excavated by heavy machinery such as the backhoe 112 (removal of excavation sludge backfilled) and mounted on the mobile pier 111. The spraying machine 113 sprays the invert part, attaches the sheet, arranges the reinforcing bars, and places the concrete by the invert mold 114, thereby forming the lining concrete 115 (invert concrete) of the invert part. As shown in FIG. 2 (c), the invert form 114 is supported by the guide rail 116 so as to advance, and is disposed in a state of passing through the movable jetty 111. When the concrete is placed, the uplift 114 is prevented by the support 117. It is like that.

  When the lining concrete 115 of the invert part is constructed, the road bed 118 is formed by backfilling the excavation gap thereon. As the backfill soil, excavation slip generated from the full-section tunnel excavator 102, excavation slip from the construction panel 108, or both of them may be used. 2A and 2D, the rear end of the mobile jetty 111 is supported on the road bed 118 formed as described above.

  On the rear side, as shown in FIG. 3, after the roadbed 118 is constructed to a predetermined level by further backfilling the excavation gap, side and top lining concrete 119 (arch concrete) is constructed. That is, while the sheet sticking cart 120, the rebar cart 121, and the movable centile 122 are sequentially advanced, sheet sticking, bar arrangement, and concrete placement are sequentially performed on the side portion and the top portion, thereby lining concrete 119 on the side portion and the top portion. Thus, the lining over the entire tunnel inner surface is completed.

  According to the tunnel construction method of the present embodiment, the excavation gap can be effectively used as the backfilling material for the construction board 108 and the road bed 118, and each heavy machine is placed on the temporary construction board 108 and the movable jetty 111. The invert part can be installed efficiently while running freely, and the primary lining is performed with sprayed concrete and rock bolts, which is advantageous in terms of cost compared to the primary lining with segments. The next lining can also be efficiently performed by the moving center 122. In particular, by excavating the pilot mine 101 and improving the water stop around the pilot mine 101, the main tunnel 100 is excavated, so that a large cross-section and a long-distance tunnel can be efficiently constructed even on springy ground. It is possible.

  The tunnel construction method according to the embodiment of the present invention has been described above. Next, a specific example of a full-section tunnel excavator suitable for application to the tunnel construction method (hereinafter simply referred to as a tunnel excavator), This will be described with reference to FIGS.

  4 shows a longitudinal sectional view of the tunnel excavator 1, FIG. 5 shows a front view of the tunnel excavator 1, and FIG. 6 shows an AA sectional view (a) of FIG. D sectional view (b) is shown in FIG. 7, and BB sectional view (a) and CC sectional view (b) in FIG. 4 are shown.

  The tunnel excavator 1 includes an excavator body 3 having a cutter head 2 at the front. The excavator body 3 includes a main bearing 4 that supports the cutter head 2, a plurality of reduction motors 5 that rotationally drive the cutter head 2, and a cutter head support body that houses the main bearings 4, the reduction motors 5 and the like. A cutter head support 6 constituted by 6 a is provided, and this cutter head support main body 6 a constitutes a main frame of the excavator main body 3. The cutter head support 6 has a donut shape with a hole into which the existing segment 7 enters in the center. Here, prior to excavation of the tunnel 100 by the tunnel excavator 1, the existing segment 7 is constructed on the inner wall surface of the small-diameter pilot mine 101 excavated by an appropriate rock shield excavator.

  Like the cutter head support 6, the cutter head 2 has a donut shape with a hole in the center, and the existing segment 7 is inserted into the hole, thereby expanding the ground of the outer periphery of the existing segment 7. Drilling is possible. A large number of disk cutters 8 are mounted on the face plate 2 a of the cutter head 2, and the rock head can be excavated by the rotation of each disk cutter 8 by rotating the cutter head 2 while pressing the disk cutter 8 against the face. Has been. Here, the face plate 2a of the cutter head 2 has a dome shape at both the outer peripheral end portion and the inner peripheral end portion, and particularly at the inner peripheral end portion, by forming the dome shape in this manner, A disc cutter 8 supported at both ends up to a position close to the outer peripheral surface can be arranged. In addition, at the inner peripheral end portion, the arrangement pitch of the disc cutter 8 is made denser than the face portion in order to reduce the load caused by the inclined arrangement of the disc cutter 8 as in the outer peripheral end portion. Yes.

  As shown in FIGS. 5 and 6, the cutter head 2 is provided with a plurality of (in this embodiment, twelve) openings 2c at equal intervals on the outer periphery of the face plate 2a. A guide plate (scraper) 9 of the bucket portion is arranged so as to face the surface. The guide plate 9 is disposed so as to be inclined with respect to the rotation direction of the cutter head 2 (see FIG. 6B), and a gap excavated by the face is indicated by an arrow P in FIG. 6B. As a result, it is easy to discharge backward. In FIG. 5 and FIG. 6A, reference numeral 2d denotes reinforcing ribs provided radially on the back side of the face plate 2a of the cutter head 2. Here, in FIG. 6A, the disk cutter attached to the face plate 2a is omitted for simplification.

  Further, a partition wall 2b is disposed behind the cutter head 2, and a notch 2e (see FIGS. 4 and 7A) for discharging a gap is formed below the partition wall 2b. Thus, the slip inserted by the guide plate 9 during the rotation of the cutter head 2 is smoothly taken into the chamber defined by the face plate 2a and the partition wall 2b, and the space behind the notch 2e below the partition wall 2b. To be discharged. The gap discharged from the notch 2e is collected by the gathering device 10 disposed immediately after the partition wall 2b, and is put on the belt conveyor 11 and conveyed backward.

  A heavy machine (hydraulic excavator) 12 serving both as a slip process and a segment carry-out is disposed at the rear position of the belt conveyor 11. Further, behind this heavy machine 12, a tire-type succeeding carriage 13 equipped with electrical equipment and hydraulic equipment for driving the tunnel excavator 1 is connected to the excavator main body 3 by a towing wire 14 and pulled. At the same time, a dump truck 15 (or a dump truck 107 shown in FIG. 1) for conveying the slip is arranged on the side of the succeeding carriage 13. The following carriage 13 and the dump truck 15 for transporting the slip travel on the above-described construction panel 108 which is backfilled and hardened by the excavation shear. By doing so, it is possible to run the subsequent carriage or the like without the necessity of laying rails for the subsequent carriage 13.

  As shown in FIG. 7A, seven side support and grippers (hereinafter simply referred to as “grippers”) 17 constituting the gripper device are mounted on the outer peripheral portion of the cutter head support body 6a. . This gripper device has a function of controlling the direction of the excavator main body 3 in addition to the function of holding the excavator main body 3 with respect to the pit wall subjected to diameter excavation and taking a reaction force on the pit wall to obtain a propulsive force. ing. Here, the gripper device includes a first gripper group 18 composed of a total of three grippers 17 arranged on the upper and both sides, and a total of four grippers 17 arranged on both sides of the upper and lower sides. And a second gripper group 19 made of the same.

  Each gripper 17 includes a curved plate-like shoe 20 pressed against a well wall, and four parallel-arranged ones whose one end is pivotally attached to the cutter head support body 6 a and the other end is pivotally attached to the shoe 20. A first support jack 21 and a first support jack 21 are arranged so as to intersect the first support jack 21, and one end portion is pivotally attached to the cutter head support body 6 a and the other end portion is pivotally attached to the shoe 20. It is configured to include two second support jacks (thrust jacks) 22 arranged in a letter C shape in front view. The end of the first support jack 21 is pivotally attached to the left and right of the front part of the cutter head support body 6a and the right and left of the rear part, and the end of the rod side is the end of the cylinder side. It arrange | positions so that it may be located back with respect to a part, and is pivotally attached to the rear part of the said shoe 20. FIG. On the other hand, the second support jack 22 is positioned outside the first support jack 21 in a front view, and the cylinder end is pivotally attached to the left and right of the rear portion of the cutter head support body 6a. At the same time, the rod-side end portion is disposed in front of the cylinder-side end portion and is pivotally attached to the front portion of the shoe 20.

  In the gripper device configured as described above, each first support jack 21 of the first gripper group 18 is extended to press the shoe 20 against the well wall, and each first support jack 21 of the second gripper group 19 is The shoe 20 is pressed against the pit wall and extended to hold the cutter head support body 6a against the pit wall.

  In this state, when the second support jack 22 of the first gripper group 18 and the second support jack 22 of the second gripper group 19 are contracted at the same time, the cutter head support body 6a moves forward and the propulsive force is increased. Then, the cutter head 2 mounted in front of the cutter head support body 6a excavates the face of the existing segment 7 outer periphery. When the second support jack 22 contracts, the first support jack 21 is controlled to expand in accordance with the contraction of the second support jack 22 while maintaining the pressing force of the shoe 20 against the well wall.

  Next, when the second support jack 22 is contracted to the maximum stroke position, first, the first support jack 21 of the second gripper group 19 is contracted to separate the shoe 20 from the well wall, and in this state, the second gripper group The 19 second support jacks 22 are extended to move the shoe 20 forward. Subsequently, the first support jack 21 of the second gripper group 19 is extended again and the shoe 20 is pressed against the well wall to hold the cutter head support body 6a against the well wall.

  Next, this time, the first support jack 21 of the first gripper group 18 is contracted to separate the shoe 20 from the well wall. In this state, the second support jack 22 of the first gripper group 18 is extended to extend the shoe 20. Move forward. Subsequently, the first support jack 21 of the first gripper group 18 is extended again and the shoe 20 is pressed against the pit wall to complete the refilling. In this way, excavation work is proceeding sequentially.

  In addition to the gripper device, a segment disassembly device 23, a work deck 24, a segment carry-out device 25, a support device 26, and the like are attached to the cutter head support body 6a. This will be described below.

  The segment disassembly device (segment disassembly erector) 23 includes a revolving ring 23a that is rotatably supported on the inner peripheral portion of the cutter head support body 6a, a hydraulic motor 23b that rotationally drives the revolving ring 23a, and A guide block 23c fixed to the swivel ring 23a, a guide rod 23d supported by the guide block 23c so as to be movable in the radial direction, and an erector main body 23e connected to the guide rod 23d and having a gripping member at a tip end thereof. A hydraulic cylinder or the like that moves the erector main body 23e in the radial direction is provided. The segment disassembling apparatus 23 sequentially disassembles the existing segments 7 that have entered the machine of the excavator main body 3 through the hole in the center of the cutter head 2 as the excavator main body 3 advances, and places the segment 7 on the work deck 24. .

  The work deck 24 is installed in order to perform the dismantling work of the existing segment 7 by the segment disassembling device 23, and is disposed so as to be positioned at a substantially central portion of the excavator body 3. Further, a slide type deck portion 24a is provided at the front portion of the work deck 24, and can be projected forward through the turning ring 23a as required.

  The segment unloading device 25 is for unloading the segment 7 disassembled by the segment demolition device 23. The segment unloading device 25 extends forward through the turning ring 23a, and the traveling rail 25a includes The hoist 25b travels along the hoist 25b. The segment 7 is suspended from the hoist 25b, and the segment 7 passes through the swivel ring 23a and is carried out backward.

  The support device 26 is a device for supporting the tunnel pit wall after the diameter expansion excavation, and is provided on the outer peripheral portion of the cutter head support body 6a. The support device 26 is configured to spray the spray material onto the pit wall by a turning type spray manipulator. In addition, as this support apparatus, the support erector etc. which assemble a support steel material can also be used.

  This tunnel excavator 1 is used when excavating a large-section tunnel in geology where the natural ground is rock and for some reason the water needs to be stopped. The procedure of excavation work is as follows.

(1) First, the small-diameter pilot mine 101 is excavated while winding up the segment 7 with a rock shield excavator. By excavating the pilot mine 101, the geology can be grasped in advance over the entire tunnel.
(2) Improving the water stop and retaining the mountain by injecting a chemical solution from the inside of the excavated pilot mine 101 to the periphery thereof.
(3) Next, the pilot pit 101 is expanded in diameter by rotating the cutter head 2 along the outer periphery of the existing segment 7 of the pilot pit 101 and propelling the excavator body 3. At this time, the gripper device (the first gripper group 18 and the second gripper group 19) performs excavation while taking a propulsive reaction force on the well wall, and the segment dismantling device 23 is installed by excavating the excavator main body 3. The segment 7 is dismantled, and the segment 7 is unloaded to the rear of the tunnel by the segment unloading device 25 and the heavy machine 12. Further, the slip taken into the machine during excavation is discharged from the notch 2c formed in the back plate 2b of the cutter head 2 to the rear space. Next, the discharged gap is accumulated by the gathering device 10 disposed immediately after the back plate 2b, and is conveyed rearward by the belt conveyor 11 and further the dump truck 15 for gap conveyance, and the backfilling material of the construction panel 108 Use as
(4) The pit wall formed by the diameter-expanded excavation is solidified by the support device 26 configured by a swirling spray manipulator. In addition, you may support a well wall using a support erector etc. as needed.

  According to this tunnel excavator 1, the disassembled segment 7 and excavation sludge are both carried out to the rear of the tunnel excavator 1 while performing diameter expansion excavation along the outer periphery of the existing segment 7 of the pilot mine 101. Therefore, not only the work on the face side of the pilot mine 101 is unnecessary, but it is only necessary to provide the work base at one place on the rear side of the excavator body, so there is an advantage even if it is placed on securing the base. is there. In addition, as a gripper device, a side support and gripper having both functions of a front side support and a main gripper in a normal rock tunnel excavator (TBM) is used, so the structure can be simplified and the cost can be reduced. There is an effect that can be. Of course, prior to excavation of the tunnel 100, the pilot mine 101 is excavated and the water around it is improved. Therefore, there is an advantage that risk in excavation of large-section rock mass can be reduced and safe and reliable construction can be performed.

  FIG. 8 shows a longitudinal sectional view of another tunnel excavator 1A.

  In the tunnel excavator 1A of this example, there is basically no difference from the previous tunnel excavator 1 except that the segment dismantling device 23A is provided separately from the excavator body 3A. Therefore, the same reference numerals are given to the portions common to both, and the detailed description thereof is omitted.

  In the tunnel excavator 1A of this example, the segment dismantling device 23A includes an elector carriage 28 that travels along a rail 27 laid from the front base side in the pilot mine 101 surrounded by the existing segment 7, and this elector carriage 28, a guide block 23c that is mounted on the end face 28 and supported by the swivel base 23f, and that can turn freely. A guide rod 23d that is supported by the guide block 23c so as to be movable in the radial direction, and a tip connected to the guide rod 23d. An erector main body 23e having a gripping member at a part thereof and a hydraulic cylinder or the like for moving the erector main body 23e in the radial direction are formed.

  In this example, the existing segment 7 is sequentially disassembled by the segment disassembly device 23A prior to excavation of the excavator body 3A, and the segment disassembly device 23A extends along the rail 27 in the same direction as the excavation direction of the excavator body 3A. Go running. In addition, the segment 7 after dismantling is carried out toward the base installed in the front side.

  In this example, it is necessary to provide work bases at two locations on the front side and the rear side of the excavator body 3A, but in other respects, the same operations and effects as those of the previous tunnel excavator 1 are achieved. It is.

  FIG. 9 shows a longitudinal sectional view of still another tunnel excavator 1B. In this case as well, the same parts as those in the previous example are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the tunnel excavator 1B of this example, a nose gripper device 30 is attached to the front portion of the excavator body 3B. The nose gripper device 30 has a base end supported by the excavator main body 3B and a nose gripper slide jack 31 arranged in a circumferential shape in a lattice shape, and a nose provided swingably by the nose gripper slide jack 31. A gripper frame 32, a segment disassembling device 23 </ b> B attached to the front portion of the nose gripper frame 32, and a plurality of swingable nose grippers 33 provided on the outer periphery of the nose gripper frame 32. Has been.

In this example, prior to excavation of the excavator body 3B, the existing segments 7 are sequentially disassembled by the segment disassembly device 23B attached to the nose gripper frame 32. The excavator body 3B is dug according to the following procedure.
(1) The nose gripper 33 is pressed against the well wall of the pilot well 101 to fix the nose gripper frame 32 to the well wall.
(2) The propulsion reaction force is taken from the pit wall by pressing the gripper device of the excavator main body 3B against the digged pit wall.
(3) The cutter head 2 is rotated.
(4) While operating the gripper device and the nose gripper slide jack 31, the cutter head 2 is pressed against the face to dig. When the excavation for one stroke is completed, the gripper device 17 is replaced. After the reordering, the nose gripper 33 is also reordered.
By repeating such a procedure, the segment 7 is excavated while being disassembled.

  According to this example, since the nose gripper 33 can be stretched in the pilot mine 101, there is an advantage that the direction controllability and stability at the time of replacement are improved as compared with the above examples.

It is a figure which shows the process in the forefront part in the tunnel construction method which is one Embodiment of this invention. It is a figure which shows the process in the back as well. It is a figure which shows the process in the back further. It is a longitudinal section showing an example of a full section tunnel excavator suitable for application to the present invention. FIG. FIG. 5 is a cross-sectional view taken along the line A-A in FIG. 4 and a cross-sectional view taken along the line DD in FIG. FIG. 5 is a BB sectional view (a) of FIG. 4 and a CC sectional view (b) of FIG. 4. It is a longitudinal section showing other examples of a full section tunnel excavator. It is a longitudinal cross-sectional view which shows the further another example of a full section tunnel excavator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Tunnel 101 Pilot mine 102 (1, 1A, 1B) Full section tunnel excavator 108 Construction panel 111 Mobile jetty 114 Invert formwork 115 Covering concrete 118 Roadbed 119 Covering concrete 122 Mobile center

Claims (2)

While excavating the tunnel with a full-section tunnel excavator,
Later, a part of the excavation slip discharged from the full-section tunnel excavator is rolled out to the bottom of the tunnel to form a construction panel, and concrete is sprayed on the side and top walls of the tunnel and rock bolts are applied. Set up
On the rear side, a mobile pier where heavy machinery can travel is provided, and the construction panel is excavated within the span of the mobile pier to form lining concrete on the invert part,
Furthermore, on the lining concrete of the invert part, the excavation gap from the full-section tunnel excavator or the excavation gap from the construction board or both of them are formed to form a roadbed, and the mobile type A tunnel construction method characterized in that lining concrete is formed on the side and top of the tunnel with a centle. In the tunnel construction method of Claim 1,
Prior to excavation of the tunnel with a full-section tunnel excavator, a pilot pit with a smaller diameter was excavated and covered with segments,
By working from the inside of the pilot mine, the ground outside the excavation cross section of the tunnel to be built is improved.
Thereafter, the tunnel construction method is characterized by excavating the surrounding ground of the pilot mine with a full-section tunnel excavator while dismantling and removing the pilot mine segment.

Images