JP6150096B2 - Tunnel excavation method - Google Patents

Description

  The present invention relates to a method for constructing a support work and a tunnel excavation method using the support work constructed by this method.

  In recent years, as a method for more efficiently constructing a shield tunnel with a large cross section, a drilling device equipped with an annular cutter portion has previously excavated the ground at a position corresponding to the outer portion of the tunnel into an annular cross section. The process of constructing the lining body in a cylindrical shape in the part and the process of propelling the excavating device by taking the reaction force on the lining body is preceded by excavating the ground in a cross-sectional annular shape, and in parallel with this A method of constructing a tunnel by excavating sediment remaining in a columnar shape inside the lining body from the rear side is known.

  The applicants of the present application have developed a drilling device capable of changing the direction of excavation during excavation as a drilling device used for excavation of such a tunnel (see, for example, Patent Documents 1 and 2).

Japanese Patent No. 5138821 Japanese Patent No. 4934234

  Here, after excavating the ground using the apparatus described in Patent Document 1, it is necessary to support the natural ground by supporting work until the lining is provided. As such a support work, the NATM construction method is widely used to assemble a steel frame after excavation, spray concrete onto the surface of the excavation hole, and place rock bolts to support the natural ground.

  However, the spray concrete used in the NATM construction method has a maximum coarse aggregate of about 15 mm, so about 30% of the material rebounds from the wall surface of the excavation hole. In addition, there is a problem that the working environment in the mine deteriorates because of the large amount of dust. Further, such shot concrete rebound and dust enter the gaps of the excavator and cause the excavator to malfunction.

  The present invention has been made in view of the above problems, and an object of the present invention is to enable a support work to be constructed without using sprayed concrete as much as possible after excavating the ground with an excavator.

The support construction method of the present invention is a method of constructing a support work on the surface of a natural ground exposed on the inner surface of a drilling hole excavated in a circular cross-sectional shape, and on the surface of the natural ground exposed on the inner surface of the drilling hole. A step of spraying the spraying mortar, a step of assembling the steel material in an annular shape along the surface of the spraying mortar, a step of installing an inner mold in an annular shape with a space from the surface of the spraying mortar inside the spraying mortar, Placing concrete between the spray mortar and the inner mold.
In the above method, preferably, after the step of assembling the steel material in an annular shape, the step of constructing an invert inside the sprayed mortar is performed below the excavation hole.

  According to the support construction method described above, since the reinforced concrete is constructed in an annular shape inside after spraying the spray mortar, the support can be constructed without using the spray concrete. Thereby, the splashing concrete can be prevented from rebounding and the generation of dust can be prevented, and a failure of the excavator can be prevented.

  The method for excavating a tunnel of the present invention includes a step of forming an excavation hole having a circular cross section using an excavator, and a mortar sprayed on the surface of a natural ground exposed on the inner surface of the excavation hole at the rear of the excavator. A step of spraying, a step of assembling a steel material in an annular shape inside the spraying mortar, a step of installing an inner mold in an annular shape with a space from the surface of the spraying mortar inside the spraying mortar, and a spraying mortar and an inner mold A step of placing concrete between the frame and a step of constructing a support work inside the excavation hole, and a step of covering the inside of the support work.

  In the above excavation method, the step of forming the excavation hole having a circular cross-sectional shape includes the step of excavating the natural ground in an annular shape by a cylindrical excavator, and the inside of the portion excavated in an annular shape inside the excavator. And excavating the natural ground.

  ADVANTAGE OF THE INVENTION According to this invention, after excavating the ground with an excavation apparatus, a support work can be constructed without using sprayed concrete.

1 is a perspective view showing an excavator according to a first embodiment of the present invention. It is a vertical sectional view of the axial direction of the excavator shown in FIG. It is a horizontal sectional view of the front-end | tip part of the excavation apparatus shown in FIG. It is an AA view side view in FIG. FIG. 3 is a cross-sectional view taken along the line B-B in FIG. 2. It is CC sectional view taken on the line in FIG. It is a vertical sectional view showing tunnel excavation using the excavator according to the first embodiment of the present invention. It is a figure for demonstrating the propulsion method in the excavation apparatus by 1st Embodiment of this invention, and shows the state which extended the back radial hydraulic jack. It is a figure for demonstrating the propulsion method in the excavation apparatus by 1st Embodiment of this invention, and shows the state which extended the front and back axial hydraulic jack. It is a figure for demonstrating the propulsion method in the excavation apparatus by 1st Embodiment of this invention, and the state which extended the front radial hydraulic jack and retracted the rear radial hydraulic jack is shown. It is a figure for demonstrating the propulsion method in the excavation apparatus by 1st Embodiment of this invention, and shows the state which contracted the front and back axial hydraulic jacks. It is a figure for demonstrating the construction method of a support work. It is a vertical sectional view of a tunnel showing an inner mold.

Hereinafter, a drilling rig which is a 1st embodiment of the present invention is explained in detail, referring to drawings.
1 is a perspective view showing the excavator 1 according to the present embodiment, FIG. 2 is a vertical sectional view in the axial direction of the excavator 1 shown in FIG. 1, and FIG. 3 is a front end portion of the excavator 1 shown in FIG. It is a horizontal sectional view. 4 is a side view taken along line AA in FIG. 2, FIG. 5 is a sectional view taken along line BB in FIG. 2, and FIG. 6 is a sectional view taken along line CC in FIG.

  As shown in FIGS. 1 and 2, the excavation apparatus 1 includes a cylindrical shell 2, a excavation mechanism 4 provided at the tip of the shell 2 in the excavation progress direction (hereinafter referred to as the front), and excavation soil discharge. A mechanism 6 and a propulsion mechanism 8 for propelling the excavation mechanism 4 are provided.

  As shown in FIG. 2, the shell 2 includes a first excavation shell 10, a second excavation shell 12, a front shell 14, and a rear shell 16 that are sequentially connected from the front. It consists of.

  The first excavation shell 10 includes an annular tip surface portion 10A forming a tip surface, a cylindrical front outer cylinder 10B extending rearward from the outer peripheral edge of the tip surface portion 10A, and a rear outer cylinder body 10B. A rear outer cylindrical body 10C connected to the end and formed in a cylindrical shape having a smaller diameter than the front outer cylindrical body 10B, a cylindrical inner cylindrical body 10D extending rearward from the inner peripheral edge of the distal end surface portion 10A, and front and rear It has a plurality of support members (not shown) provided so as to connect the outer cylinders 10B and 10C and the inner cylinder 10D.

  The second excavation shell 12, the front shell 14, and the rear shell 16 are each formed to have substantially the same diameter as the front outer cylinder 10 </ b> B of the first excavation shell 10. Cylindrical outer cylinders 12C, 14C, and 16C, and cylindrical cylinders that are disposed within the outer cylinders 12C, 14C, and 16C and have substantially the same diameter as the inner cylinder 10D of the first excavation shell 10 The inner cylinders 12D, 14D, and 16D, and a plurality of support members (not shown) provided to connect the inner cylinders 12D, 14D, and 16D and the outer cylinders 12C, 14C, and 16C. These shells 10, 12, 14, and 16 are each made of steel. Note that the second end is formed such that a gap 10F is formed between the rear end of the inner cylinder 10D of the first excavation shell 10 and the front end of the inner cylinder 12D of the second excavation shell 12. The excavation part shell 12 terminates in front of the front end of the inner cylinder 12D.

  Inner cylinders 10D, 12D, 14D, 16D and outer cylinders 10B, 10C constituting the first excavation part shell 10, the second excavation part shell 12, the front shell 14, and the rear shell 16 , 12C, 14C, and 16C are arranged concentrically with a rotation shaft of the excavation mechanism 4 described in detail later, whereby the inner cylinders 10D, 12D, 14D, and 16D and the outer cylinders 10B, 10C, and 12C, An annular space is formed between 14C and 16C. The support member is made of a rod-shaped or plate-shaped steel material, and the number of the inner cylinders 10D, 12D, 14D, and 16D that can support the earth pressure acting on the outer cylinders 10B, 10C, 12C, 14C, and 16C, The inner cylinders 10D, 12D, 14D, and 16D and the outer cylinders 10B, 10C, 12C, 14C, and 16C are connected to each other radially at an appropriate interval in the circumferential direction and the axial direction. . The propulsion mechanism 8 is accommodated in an annular space between the inner cylinders 10D, 12D, 14D, and 16D and the outer cylinders 10B, 10C, 12C, 14C, and 16C.

  The rear outer cylinder 10C of the first excavation shell 10 is housed inside the outer cylinder 12C of the second excavation shell 12 so that the first excavation shell 10 is The two excavation shells 12 are rotatably connected. Note that the rear outer cylindrical body 10 </ b> C of the first excavation part shell 10 can improve slippage by interposing a bearing or the like with the outer cylinder 12 </ b> C of the second excavation part shell 12.

  The second excavation part shell 12 is cut out at the rear end of the inner peripheral surface of the inner cylinder 12D and the rear end of the outer peripheral surface of the outer cylinder 12C. Further, the front shell body 14 is cut out at the distal end portion of the outer peripheral surface of the inner cylindrical body 14D and the distal end portion of the inner peripheral surface of the outer cylindrical body 14C. And by accommodating the front-end | tip part of the front shell 14 inside the rear-end part of the 2nd excavation part shell 12, the 2nd excavation part shell 12 is with respect to the front shell 14 It is slidably connected in the axial direction.

  Similarly, the front shell 14 has a rear end portion of the inner peripheral surface of the inner cylindrical body 14D and a rear end portion of the outer peripheral surface of the outer cylindrical body 14C cut out. Further, the rear shell body 16 is cut out at the distal end portion of the outer peripheral surface of the inner cylindrical body 16D and the distal end portion of the inner peripheral surface of the outer cylindrical body 16C. The front shell 14 can slide in the axial direction with respect to the rear shell 16 by accommodating the tip of the rear shell 16 inside the rear end of the front shell 14. It is connected to the. A guide member that guides the sliding in the axial direction may be provided at the connection portion between the second excavation shell 12 and the front shell 14 and between the front shell 14 and the rear shell 16. .

  As shown in FIG. 3, the excavation mechanism 4 includes a cutter unit 20 including a plurality of drill bits formed in the tip surface portion 10 </ b> A of the first excavation unit shell 10, and the first excavation unit shell 10. The reduction gear 22 arrange | positioned and the motor 24 arrange | positioned in the 2nd excavation part shell 12 are provided.

  As shown in FIG. 4, a plurality of openings 26 are formed in the distal end surface portion 10 </ b> A of the first excavation shell 10 at intervals in the circumferential direction. The space 10 </ b> E communicates through the opening 26.

  The cutter unit 20 is provided on the edge of the opening 26 formed in the tip surface portion 10A and the 13 pairs of roller bits 28 provided in the tip surface portion 10A of the first excavation shell 10 at intervals in the circumferential direction. A drill bit 30 is provided.

  As shown in FIG. 3, a pin rack 32 is attached to the rear end portion of the first excavation shell 1.

  As shown in FIG. 3, a motor 24 is disposed in the second excavation shell 12, and a speed reducer 22 is connected to the rotating shaft of the motor 24, and a pinion 22 </ b> A is attached to the speed reducer 22. It has been. The pinion 22A attached to the speed reducer 22 meshes with the pin rack 32 attached to the first excavation part shell 10. As a result, when the motor 24 rotates, the torque is amplified through the speed reducer 22 and transmitted to the first excavation shell 10, and the first excavation shell 10 is centered on its central axis. And rotate with respect to the second excavation shell 12.

  Each roller bit 28 is disposed at a different position in the radial direction. As a result, when the first excavation shell 10 rotates in the circumferential direction, the trajectory through which each roller bit 28 passes becomes a concentric circle that is substantially equally spaced in the radial direction, so that uniform excavation is performed regardless of the diameter. Can do.

  The drill bit 30 is formed of a bit with a sharp tip, and the first excavation shell 10 rotates to excavate the cutting surface cut by the roller bit 28 so as to be flat.

  As shown in FIG. 2, the excavated soil discharge mechanism 6 is configured so that the space 10E in the first excavated shell 10 is divided into a plurality of chambers 10G in the circumferential direction. A plurality of plate members 34 provided in the space 10E, a closing plate 36 attached to the inner cylinder 12D of the second excavation part shell 12 so as to extend forward, and water is sprayed toward the ground As shown, the jet nozzle is provided with a jet nozzle (not shown) provided to be exposed on the surface of the front end face portion 10A of the first excavation shell 1.

  Each plate member 34 is connected to the back surface of the tip surface portion 10A of the first excavation portion shell 10 where the drilling bit 30 is attached, and the first excavation portion shell is described later. When the body 10 rotates, it is inclined in the circumferential direction so as to push the excavated soil in the space 10E backward.

  The closing plate 36 maximizes the gap 10F between the rear end of the inner cylinder 10D of the first excavation shell 10 and the front end of the inner cylinder 12D of the second excavation shell 12 in the circumferential direction. A part from the lower part to a predetermined height (in this embodiment, a part of about 120 ° on each side in the circumferential direction from the lowermost part) is provided to be closed.

  As shown in FIG. 2, the propulsion mechanism 8 extends in the direction of excavation and is connected in series to a plurality of pairs of front and rear axial hydraulic jacks 40, 42 and axial hydraulic jacks 40, 42 adjacent in the circumferential direction. A plurality of front and rear radial hydraulic jacks 44, 46 disposed between the front and rear radial hydraulic jacks 44, 46, and a plurality of front and rear support plates 48, 50 respectively connected to the front ends of the front and rear radial hydraulic jacks 44, 46. And an auxiliary propulsion jack 60.

  The front and rear axial hydraulic jacks 40, 42 of each pair are connected in series so as to extend in the excavation progress direction. The front and rear axial hydraulic jacks 40, 42 of each pair are provided at equal angular intervals in the circumferential direction of the shell body 2 so as to obtain a uniform driving force regardless of the angle.

  The front axial hydraulic jack 40 is accommodated between the inner cylinders 12D and 14D and the outer cylinders 12C and 14C from the second excavation part shell 12 to the front shell 14 and has a tip end. It is fixed to a connection plate 52 provided in the second excavation shell 12 and its rear end is fixed to a connection plate 54 provided in the front shell 14.

  The rear axial hydraulic jack 42 is accommodated between the inner cylinders 14D and 16D and the outer cylinders 14C and 16C from the front shell body 14 to the rear shell body 16, and the tip is the front shell body. The body 14 is fixed to the connection plate 54, and the rear end is fixed to the connection plate 56 provided on the rear shell 16. As described above, the front and rear axial hydraulic jacks 40 and 42 are connected in series via the connection plate 54.

  As shown in FIG. 5, the front radial hydraulic jack 44 is provided with a pair of two hydraulic jacks arranged in the circumferential direction with respect to a rectangular support plate 48. The paired radial hydraulic jacks 44 are accommodated in the second excavation shell 12 at intervals in the circumferential direction.

  Further, as shown in FIGS. 2 and 6, the rearward radial hydraulic jack 46 includes four hydraulic jacks as a set for each of the pair of support plates 50 arranged in the front-rear direction. It is provided at a position corresponding to the four corners. The rear radial hydraulic jack 46 is accommodated in the rear shell 16 at intervals in the front-rear direction and the circumferential direction.

Openings 12A and 16A are formed in the outer cylinders 12C and 16C of the second excavation shell 12 and the rear shell 16 at positions corresponding to the front and rear radial hydraulic jacks 44 and 46, respectively. One end of each of the front and rear radial hydraulic jacks 44, 46 is fixed to the second excavation shell 12 and the inner cylinders 12D, 16D of the rear shell 16, and the other end is an outer cylinder 12C. The openings 12A and 16A formed in 16C are connected to support plates 48 and 50 having substantially the same shape. With this configuration, the front and rear radial hydraulic jacks 44 and 46 extend, and the support plates 48 and 50 protrude toward the outer periphery.
The axial hydraulic jacks 40 and 42 and the radial hydraulic jacks 44 and 46 are connected to a control device (not shown), and hydraulic pressure is supplied by the control device.

Hereinafter, a tunnel excavation method using the excavator 1 will be described.
FIG. 7 is a vertical sectional view showing tunnel excavation using the excavator 1 according to the present embodiment. As shown in the figure, in the present embodiment, the ground 62 is excavated in a cylindrical shape by the excavator 1, followed by excavating the remaining ground 64 in the center by a heavy machine 66. Build a tunnel with a circular cross section. A gantry 68 that is movable with the digging device 1 is provided behind the digging device 1, and the heavy machinery 66 is placed on the gantry 68.

  First, a method of propelling the excavation mechanism 4 by the propulsion mechanism 8 will be described with reference to FIGS. This propulsion work is performed while rotating the cutter unit 20 of the excavating mechanism 4 about the axis of the excavating device 1 and discharging the excavated soil by the excavated soil discharging mechanism 6.

  First, as shown in FIG. 8, with the front and rear axial hydraulic jacks 40, 42 contracted, the rear radial hydraulic jack 46 is extended and the surrounding ground is pressed by the support plate 50. Then, as shown in FIG. 9, with the reaction force applied to the ground by the support plate 50, the front and rear axial hydraulic jacks 40, 42 are extended to push the excavation mechanism 4 forward, and the excavation mechanism 4 The ground is excavated into a cylindrical shape.

  In this way, after excavation for a predetermined distance, as shown in FIG. 10, the front radial hydraulic jack 44 is extended and the surrounding ground is pressed by the support plate 48. Then, the rear radial hydraulic jack 46 is retracted.

  Further, as shown in FIG. 11, the front and rear axial hydraulic jacks 40, 42 are contracted. Thereby, the front and rear shells 14 and 16 can be advanced. At this time, the front and rear shell bodies 14 and 16 can be easily extended by extending the auxiliary propulsion jack 60 in a state where the reaction force is applied to the segment attached to the inner peripheral wall of the tunnel that has been excavated. You can move forward.

  By repeating the above steps, the excavating mechanism 4 can be advanced forward and the excavator 1 can be propelled.

  Along with the above propulsion work, the cutter unit 20 is rotated to excavate the ground, and excavated soil generated by the excavation is sent to the rear of the apparatus. That is, the motor 24 of the excavation mechanism 4 is rotated in a state where the cutter unit 20 is pressed against the ground by the propulsion mechanism 8. The rotational force of the motor 24 is transmitted to the speed reducer 22 to amplify the torque, and the first excavation part shell 10 is rotated via the pinion 22A and the pin rack 32. When the first excavation part shell 10 rotates, the ground is first excavated into a cross-sectional saw shape by the roller bit 28 of the cutter unit 20, and the surface irregularities are cut by the drill bit 30. Thereby, the ground can be excavated in an annular shape.

  The excavated soil produced by excavating the ground with the cutter unit 20 is agitated with the water sprayed from the jet nozzle, and the fluidity is improved. Then, the excavated soil is accommodated in the chamber 10G in the first excavation shell 10 from the opening 26 formed in the front end surface portion 10A of the first excavation shell 10. Then, when the first excavation part shell 10 is rotated, the first excavation part shell 10 is sent backward by the plate member 34 attached in the first excavation part shell 10, and is discharged from the gap 10F to the space inside the apparatus.

  Here, as described above, the gap 10F between the rear end of the inner cylinder 10D of the first excavation shell 10 and the front end of the inner cylinder 12D of the second excavation shell 12 is a circumferential direction. The part from the lowest part to a predetermined height is closed by the closing plate 36. For this reason, excavated soil is not discharged from the chamber 10G positioned below the predetermined height, and the inside of the chamber 10G rotated to a predetermined height by the rotation of the first excavation shell 10 The excavated soil falls on the closing plate 36. Thereby, it is possible to prevent the excavated soil carried to the gap 10F through the chamber 10G from accumulating downward and closing the gap 10F.

In parallel with the preceding excavation work, the ground 64 inside the portion excavated in an annular shape by the excavator 1 is excavated to the rear position of the first excavation part shell 10. For this excavation work, a heavy machine such as a breaker or a backhoe may be used.
Then, the excavated soil carried by the blades and the excavated soil generated by excavating the ground are loaded on a dump truck by a shaflower and carried out of the tunnel.

Next, a support work is constructed in the part where excavation of the entire section of the tunnel is completed.
Hereinafter, the construction method of the support construction will be described with reference to FIG. In FIG. 12, (A), (B), and (D) show the vertical section of the upper part of the tunnel behind the apparatus, and (C) shows the vertical section of the lower part of the tunnel behind the apparatus.

  First, when the excavator 1 advances forward by the method described with reference to FIGS. 8 to 11, as shown in FIG. 12A, the surface of the ground 62 exposed in the excavation hole at the rear of the apparatus 1. The spraying mortar 70 is sprayed toward. Since this sprayed mortar 70 does not contain aggregate, it does not bounce like sprayed concrete. Also, the sprayed mortar 70 generates very little dust compared to sprayed concrete.

  Next, as shown in FIG. 12B, the steel material 72 is built in an annular shape along the surface of the sprayed mortar 70 at the tip of the surface of the sprayed mortar 70 in the excavation progress direction.

  Next, as shown in FIG. 12C, inverted concrete 74 is placed below the excavation hole.

  Next, reinforcing bars are arranged in a lattice pattern along the surface of the sprayed concrete 62. Then, a telescopic inner mold frame 76 as shown in FIG. 13 is sprayed and arranged at a distance from the surface of the mortar 70. The inner mold 76 is made of a steel material assembled in an annular shape having a width that is substantially equal to the distance traveled by a single propulsion operation of the excavator 1. Further, the inner mold 76 can be deformed from the expanded state shown in FIG. 13 to a contracted state toward the central direction. The inner mold 76 may be fixed to a gantry 68 that can move together with the excavator 1.

  Next, concrete 78 is placed between the sprayed mortar 70 and the inner mold 76. The concrete 78 to be placed at this time is preferably a highly fluid concrete. When the cast concrete 78 is hardened, the inner mold 76 can be contracted and moved forward in the direction of excavation and used again.

  Then, when the placement of the concrete 78 is completed, as shown in FIG. 12D, the excavator 1 is propelled forward by a predetermined distance by the method described with reference to FIGS.

  Through the above steps, the support work 80 can be sequentially constructed behind the excavation apparatus 1, and the support work 80 can suppress the natural ground 62 that has been excavated from collapsing. According to the support 80 constructed in this way, since it has an annular reinforced concrete layer inside, it has a sufficient function as a support.

  Then, behind the support construction 80, the inside of the support construction is covered with a segment or the like. Thereby, a tunnel with a circular cross section can be constructed.

  As described above, according to the present embodiment, after the spraying mortar 70 is sprayed, the reinforced concrete layer is constructed in an annular shape inside the spraying mortar 70. Therefore, the support 80 is constructed without using the sprayed concrete. be able to. Thereby, the splashing concrete can be prevented from rebounding and the generation of dust can be prevented, and a failure of the excavator 1 can be prevented.

  Moreover, in the NATM construction method, the lock bolt was driven to fix the shotcrete, but according to this embodiment, it is not necessary to drive the lock bolt, and the support work can be constructed in a short time. Can improve the speed of tunnel construction.

  In this embodiment, the excavator 1 excavates the ground in an annular cross section and then excavates the remaining portion. However, the present invention is not limited to this, and the tunnel is excavated by the so-called TBM method. If it exists, the construction method of the support work of this invention is applicable.

DESCRIPTION OF SYMBOLS 1 Excavator 2 Shell body 4 Excavation mechanism 6 Excavation soil discharge mechanism 8 Propulsion mechanism 10 1st excavation part shell body 10A Front end surface part 10B Front outer cylinder body 10C Rear outer cylinder body 10E Space 10F, 110F Gap 10G Chamber 12 Second Excavation shells 12C, 14C, 16C Outer cylinders 10D, 12D, 14D, 16D, 12E Inner cylinder 20 Cutter part 26 Opening 28 Roller bit 30 Drilling bit 34 Plate material 36 Closing plate 40, 42 Axial hydraulic jack 44, 46 radial hydraulic jacks 48, 50 Support plate 60 Propulsion jack 62 Concrete 62 Ground (ground)
66 Heavy machinery 68 Base 70 Spraying mortar 72 Steel 74 Invert concrete 76 Inner form 78 Concrete 80 Support

Claims (1)

A method of excavating a tunnel,
A step of forming a borehole circular cross section with a drilling device, the step of forming a borehole of the circular cross-sectional shape includes the steps of drilling a natural ground as a ring by a cylindrical drilling apparatus, wherein A step of excavating a natural ground inside the annularly excavated portion inside the excavator, and a platform that is movable with the excavator is provided behind the cylindrical excavator. In the excavator, the step of excavating the natural ground inside the annularly excavated portion is performed by a heavy machine placed on the gantry,
The method further includes the step of spraying mortar on the surface of the ground exposed on the inner surface of the excavation hole behind the excavator, assembling a steel material in an annular shape inside the spray mortar, and the spraying By placing the inner mold in an annular shape with an interval from the surface of the spray mortar inside the mortar, and placing the concrete between the spray mortar and the inner mold, A step of constructing a supporting work inside the excavation hole, wherein the inner mold frame can be contracted in a radial direction, and in the step of installing the inner mold frame, the inner mold frame is supported by the gantry Installed with expanded,
The method further comprises:
A tunnel excavation method comprising: lining the inside of the support work.

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