JP6989326B2 - Tunnel construction method - Google Patents

Description

The present invention relates to a tunnel construction method.

Patent Document 1 proposes a long steel pipe tip receiving method in which two or more steel pipes are arranged one above the other in the cross section of the first receiving section. In this long steel pipe tip receiving method, each steel pipe to be cast has a plurality of pipes having different axial lengths, and the joint portion of each pipe is axially formed between the plurality of steel pipes. By making them different, the weak points of the steel pipe rigidity are dispersed.

Japanese Unexamined Patent Publication No. 2014-062385

The problems of the conventional tunnel construction method exemplified in Patent Document 1 will be described with reference to FIGS. 1 and 2. 1 and 2 are a vertical sectional view and a horizontal sectional view schematically illustrating a tunnel construction method according to a conventional example. In the conventional tunnel construction method, the tunnel 80 is dug by excavating the ground at predetermined intervals.

In the area where the ground has been excavated, a (steel) support 90 is installed in the circumferential direction of the tunnel 80 from the ceiling surface to both sides of the tunnel 80, and the excavation resistance including the ceiling surface, both side surfaces, and the excavation surface 82. Install sprayed concrete 91 on the wall. Further, after that, the lock bolt 92 is placed as a support material for the tunnel 80 in a direction substantially orthogonal to the surface of the sprayed concrete 91, that is, in a radial direction on the ground around the tunnel.

On the other hand, in order to prevent the face 81 of the tunnel 80 from collapsing, as an auxiliary construction method (specifically, a pre-received construction) different from the support of the tunnel 80, a predetermined interval is provided in the circumferential direction for each predetermined length of tunnel excavation. Then, using the support 90 closest to the excavation surface 82 as a guide, a plurality of first reinforcing pipes 95 are driven from the excavation surface (mirror surface) 82 at a predetermined elevation angle toward the ground in front of the face, and injected into and out of the reinforcing pipe 95. Inject wood to integrate the ground. At this time, a part of the rear end of each first reinforcing pipe 95 is driven into the area 83 to be excavated located in front of the excavation surface 82 in the excavation direction, but most of the part of the first reinforcing pipe 95 is. It is placed in the peripheral area 84 above the area 83 to be excavated and is arranged so as to cover the upper part of the area 83.

When the tunnel 80 is further dug, the injection material injected into each of the first reinforcing pipes 95 and the surrounding ground is integrated with the ground of the peripheral region 84 on the tunnel 80 to suppress the collapse during excavation. In addition, even if the ground of the surrounding area 84 is integrated, in the mountain where the ground in front of the face is pushed out toward the excavation surface 82, as a further auxiliary construction method (specifically, mirror reinforcement work), the ground is directed toward the front in the excavation direction. By driving a plurality of second reinforcing pipes 96 in the horizontal direction from the excavation surface 82 and injecting an injection material around them as needed, the ground in front of the face was reinforced and the stability was improved. Therefore, in the conventional tunnel construction method, two types of reinforcing pipes, the first reinforcing pipe 95 and the second reinforcing pipe 96, are placed in a separate process for each predetermined excavation length, which is a temporary material different from the support. There is a problem that the construction efficiency of the auxiliary construction method is poor and the cost is high.

When the tunnel 80 is further dug after the auxiliary construction method is constructed, the ground is excavated together with a part of the rear end of each first reinforcing pipe 95 and each second reinforcing pipe 96. In this process, the remaining portion of each first reinforcing pipe 95 integrates the peripheral region 84 so as to serve as a pre-receiver as the existing reinforcing pipe 95A. Further, behind the face 81, a waterproof sheet (not shown) is laid on the surface of the sprayed concrete 91, a mobile formwork is set, and the secondary lining concrete 93 is constructed. When these steps are completed within the desired range, the tunnel 80 is completed.

The present invention has been made in consideration of such a point on one aspect, and an object of the present invention is to provide a tunnel construction method capable of efficiently reinforcing the ground in front of the face at low cost. Is.

The present invention adopts the following configuration in order to solve the above-mentioned problems.

That is, the tunnel construction method according to one aspect of the present invention is a step of digging a tunnel by excavating a ground and the tunnel from the ceiling surface to both sides of the tunnel in the excavated area of the ground. A step of installing a support in the circumferential direction of the tunnel and a step of placing a plurality of reinforcing pipes at a predetermined interval in the circumferential direction on the excavated surface of the face of the tunnel, from the excavated surface to the tunnel. The plurality of reinforcements are placed in the first part to be driven in the first area to be excavated located in front of the excavation direction of the above, and the second part to be placed in the second area adjacent to the outside of the first area in the radial direction. As each of the pipes has, a step of placing each of the plurality of reinforcing pipes at a predetermined elevation angle with respect to the excavation direction is provided at a position separated inward in the radial direction from the support.

In the tunnel construction method, a plurality of reinforcing pipes are placed on the excavated surface of the tunnel face at predetermined intervals in the circumferential direction. At this time, support work is carried out so that each reinforcing pipe has a first portion to be driven into the first region to be excavated and a second portion to be driven into the second region adjacent to the outside in the radial direction of the first region. Each reinforcing pipe is placed at a position separated from the inside in the radial direction at a predetermined elevation angle with respect to the excavation direction.

As a result, the second part of each reinforcing pipe functions as a pre-receiver that suppresses the collapse of the face from the second region, while the first part of each reinforcing pipe is a mirror that enhances the stability of the ground in front of the face. It can function as a reinforcement work. That is, each reinforcing pipe can have two roles of a pre-receiver and a mirror reinforcing pipe. Therefore, according to the present invention, it is possible to efficiently reinforce the ground in front of the face at low cost.

Further, in the tunnel construction method according to the one side surface, each of the plurality of reinforcing pipes is placed at a position 900 mm to 1300 mm inward in the radial direction from the support in order to reinforce the excavated surface by the first portion. May be done. According to this configuration, the stability of the ground in front of the face can be sufficiently enhanced by the first portion of each reinforcing pipe.

Further, in the tunnel construction method according to the one side surface, the plurality of reinforcing pipes are placed so that the ratio of the first portion to the second portion is 1: 0.8 to 1: 1.2. It's okay. According to this configuration, the roles of the pre-receiver and the mirror reinforcement work can be fully exerted in each of the first part and the second part. Therefore, according to the configuration, the face can be appropriately reinforced.

Further, in the tunnel construction method according to the one side surface, each of the plurality of reinforcing pipes may be driven at an elevation angle of 8 to 12 degrees with respect to the excavation direction. According to this configuration, the roles of the pre-receiver and the mirror reinforcement work can be fully exerted in each of the first part and the second part. Therefore, according to the configuration, the ground in front of the face can be reinforced more appropriately.

Further, in the tunnel construction method according to the one side surface, at least the first portion of each of the plurality of reinforcing pipes may be provided with one or a plurality of slits so as to be cut off during the excavation. According to this configuration, when further excavating the ground, it is possible to easily cut the first portion of each reinforcing pipe that will be exposed in the excavated cross section. This makes it possible to improve the workability of the tunnel.

Further, in the tunnel construction method according to the one side surface, at least the first portion of each of the plurality of reinforcing pipes may be made of a resin material that can be sheared during excavation. According to this configuration, the first portion of each reinforcing pipe can be easily cut when further excavating the ground. This makes it possible to improve the workability of the tunnel. As an example of the resin material that can be sheared, for example, fiber reinforced plastic, resin pipe, and the like can be mentioned.

According to the present invention, it is possible to provide a tunnel construction method capable of efficiently reinforcing the ground in front of the face at low cost.

FIG. 1 is a vertical sectional view illustrating a tunnel construction method according to a conventional example. FIG. 2 is a cross-sectional view illustrating the tunnel construction method according to the conventional example. FIG. 3 is a vertical cross-sectional view illustrating the tunnel construction method according to the embodiment. FIG. 4 is a cross-sectional view illustrating the tunnel construction method according to the embodiment. FIG. 5 is a perspective view illustrating the tunnel construction method according to the embodiment. FIG. 6 illustrates a scene in which each reinforcing pipe is placed according to the embodiment. FIG. 7 illustrates a scene in which each reinforcing pipe is placed according to the embodiment. FIG. 8 illustrates the reinforcing pipe according to the embodiment. FIG. 9 is a partial cross-sectional view illustrating the reinforcing pipe according to the embodiment. FIG. 10 illustrates a tunnel construction method according to an embodiment. FIG. 11 illustrates a tunnel construction method according to a comparative example. FIG. 12 shows the concept of simulation. FIG. 13A shows the simulation result of the displacement amount distribution in the AA cross section of the example. FIG. 13B shows the simulation result of the shear strain amount distribution in the AA cross section of the example. FIG. 13C shows the simulation result of the plastic region distribution in the AA cross section of the example. FIG. 14A shows the simulation result of the displacement amount distribution in the BB cross section of the example. FIG. 14B shows the simulation result of the shear strain amount distribution in the BB cross section of the example. FIG. 14C shows the simulation result of the plastic region distribution in the BB cross section of the example. FIG. 15A shows the simulation result of the displacement amount distribution in the CC cross section of the comparative example. FIG. 15B shows the simulation result of the shear strain amount distribution in the CC cross section of the comparative example. FIG. 15C shows the simulation result of the plastic region distribution in the CC cross section of the comparative example. FIG. 16A shows the simulation result of the displacement amount distribution in the DD cross section of the comparative example. FIG. 16B shows the simulation result of the shear strain amount distribution in the DD cross section of the comparative example. FIG. 16C shows the simulation result of the plastic region distribution in the DD cross section of the comparative example.

Hereinafter, an embodiment according to one aspect of the present invention (hereinafter, also referred to as “the present embodiment”) will be described with reference to the drawings. However, the embodiments described below are merely examples of the present invention in all respects. Various improvements and modifications may be made without departing from the scope of the present invention. That is, in carrying out the present invention, a specific configuration according to the embodiment may be appropriately adopted.

§1 Construction method First, the construction method of the tunnel 10 according to the present embodiment will be described with reference to FIGS. 3 to 5. 3 to 5 are a vertical sectional view, a horizontal sectional view, and a perspective view schematically illustrating a construction method of the tunnel 10 according to the present embodiment.

(1st step)
In the present embodiment, first, a step of digging a tunnel 10 (hereinafter, also referred to as an excavation step) is carried out by excavating a ground by a predetermined excavation length. The excavation length for excavating the ground may be appropriately determined according to the embodiment. Further, the excavation process of this ground can be carried out by a known method. At this time, a known excavator may be used for excavating the ground.

(Second step)
Subsequently, as shown in each figure, a step of installing (steel) support 20 in the circumferential direction of the tunnel 10 from the ceiling surface 101 of the tunnel 10 to both side surfaces 102 in the area where the ground is excavated (hereinafter, It is also described as the support installation process). The support works 20 are installed at predetermined intervals in the excavation direction. The interval at which the support work 20 is installed may be appropriately determined according to the embodiment. Further, a known support material may be used for the support 20. For example, the support work 20 is configured by connecting a plurality of H-shaped steels in an arch shape.

As illustrated in FIG. 4, the cross section of the tunnel 10 is formed in a substantially arc shape, for example. The circumferential direction of the tunnel 10 is a direction along the arc of the tunnel 10. However, the circumferential direction does not have to be exactly along the arc. The shape of the cross section of the tunnel 10 may not be formed exactly in an arc shape, or may be formed in a shape other than an arc shape such as an elliptical shape or a circular shape. The circumferential direction may be a direction roughly along the inner circumference of the tunnel 10.

Further, after the support work 20 is installed, the sprayed concrete 21 is constructed on the excavated anti-wall including the ceiling surface 101, both side surfaces 102, and the excavated surface 12 by using a known concrete spraying machine or the like. The thickness of the sprayed concrete 21 may be appropriately determined according to the embodiment. In the place where the support 20 is present, the sprayed concrete 21 is cast so as to fill the support 20. At this time, the support work 20 may be at least partially exposed from the sprayed concrete 21 or may be completely buried in the sprayed concrete 21.

Further, after the sprayed concrete 21 is placed, a plurality of lock bolts 22 are placed at intervals in the circumferential direction in the radial direction of the tunnel 10 in order to further reinforce the tunnel 10. The placement of each lock bolt 22 can be carried out by a known method. Further, a known lock bolt may be used for each lock bolt 22. This completes the support installation process.

The radial direction is the direction in which the line connecting the inner peripheral surface (ceiling surface 101, each side surface 102) of the tunnel 10 and the tunnel axis extends. The position of the axis of the tunnel 10 is a position that can be the center of the arc shape of the upper half arch portion of the tunnel 10. FIG. 4 shows an example of the radial direction. However, the axis of the tunnel 10 does not have to be strictly defined. The radial direction may be the direction in which the line roughly connecting the vicinity of the center of the tunnel 10 and the inner peripheral surface extends.

(Third step)
Next, on the excavated surface 12 of the face 11 of the tunnel 10, a step of placing a plurality of reinforcing pipes 30 at predetermined intervals in the circumferential direction (hereinafter, also referred to as an auxiliary work installation step) is carried out. At this time, as shown in FIG. 3, in the present embodiment, each reinforcing pipe 30 is placed at a position separated from the support work 20 inward in the radial direction at a predetermined elevation angle with respect to the excavation direction. As a result, each reinforcing pipe 30 is adjacent to the first portion 31 to be driven into the first region 13 to be excavated located in front of the excavation surface 12 in the excavation direction of the tunnel 10 and to the outside of the first region 13 in the radial direction. The reinforcing pipe 30 is driven so as to have a second portion 32 to be driven in the second region.

For convenience of explanation, the distance between adjacent reinforcing pipes 30 in the circumferential direction is referred to as "pitch (P)", and the distance for separating each reinforcing pipe 30 from the support work 20 inward in the radial direction is referred to as "separation distance (separation distance)". It is referred to as "H)", and the direction (angle) of each reinforcing pipe 30 with respect to the excavation direction is referred to as "elevation angle (E)". Here, the digging direction is the direction in which the tunnel 10 is dug, and coincides with the extending direction (axial direction) of the axis of the tunnel 10.

Each reinforcing pipe 30 is formed in a substantially cylindrical shape extending in the axial direction (that is, in the longitudinal direction). Details of the configuration of each reinforcing pipe 30 and the method of placing each reinforcing pipe 30 will be described later. The length of each reinforcing pipe 30 in the axial direction may be appropriately determined according to the embodiment. The length of each reinforcing pipe 30 in the axial direction can be, for example, 15500 mm to 18500 mm (15.5 m to 18.5 m).

Further, the separation distance H in the radial direction between the support work 20 and each reinforcing pipe 30, the ratio between the first portion 31 and the second portion 32, and the elevation angle E of each reinforcing pipe 30 with respect to the excavation direction are each implemented. It may be appropriately determined according to the form.

For example, the distance H in the radial direction between the support 20 and each reinforcing pipe 30 can be 900 mm to 1300 mm because the excavated surface 12 is reinforced by the first portion 31. The ratio of the first portion 31 to the second portion 32 can be 1: 0.8 to 1: 1.2. The elevation angle E of each reinforcing pipe 30 can be 8 to 12 degrees.

It is preferable to place each reinforcing pipe 30 so as to satisfy all of these conditions. However, each reinforcing pipe 30 does not necessarily have to satisfy all of these conditions. When more than half of the plurality of reinforcing pipes 30 to be driven on the excavation surface 12 are driven so as to satisfy each of the above conditions, the placement of each reinforcing pipe 30 shall be in accordance with the above conditions. It is assumed that it is done.

Further, the pitch P of the reinforcing pipe 30 and the casting range may be appropriately determined according to the embodiment. The casting range of the reinforcing pipe 30 can be defined by the angle S of the distribution range of each reinforcing pipe 30 at the center of the tunnel 10. For example, the pitch P of the reinforcing pipe 30 can be 300 mm to 600 mm. Further, the casting range (angle S) of the reinforcing pipe 30 can be 90 degrees to 180 degrees.

The face 11 is an excavation site. The positions of the face 11 and the excavation surface 12 move forward in the excavation direction each time excavation is performed for a predetermined distance (interval) by the excavation process. The support work installation process and the auxiliary work installation process are carried out every time the excavation for a predetermined distance is completed by the excavation process. At this time, the distance to be excavated in each excavation step may be appropriately determined according to the embodiment. Further, the excavation distance does not necessarily have to be the same in each excavation process.

After the auxiliary work installation process is completed, the tunnel 10 is further dug by repeating the process from the excavation process. At this time, in the excavation process, the ground is excavated together with the first portion 31 of each reinforcing pipe 30. In this process, the second portion 32 of each reinforcing pipe 30 remains in the second region 14 as the existing reinforcing pipe 30A, and serves as a pre-receiver for suppressing the collapse of the face 11 from the second region 14. As shown in FIGS. 3 and 4, the interval at which the excavation process is carried out, that is, the interval at which each reinforcing pipe 30 is placed, is such that a plurality of reinforcing pipes 30 (30A) in the same radial direction in the cross section of the tunnel 10. Is preferably determined to overlap.

(4th step)
When the excavation of the tunnel 10 has progressed sufficiently, a waterproof sheet (not shown) is laid on the surface of the sprayed concrete 21 behind the face 11. Then, the mobile formwork is set and the secondary lining concrete 23 is constructed. When these steps are completed within the desired range, the tunnel 10 is completed. The completed tunnel 10 is in a state of being supported by a (steel) support 20, sprayed concrete 21, lock bolt 22, and secondary lining concrete 23.

[Placement method]
Next, a method of placing each reinforcing pipe 30 will be described with reference to FIGS. 6 and 7. FIG. 6 schematically illustrates a driving scene of each reinforcing pipe 30 according to the present embodiment. FIG. 7 is a partially enlarged view of FIG. Each reinforcing pipe 30 according to the present embodiment can be driven by a double pipe drilling method using a drill jumbo 60.

Specifically, the drill jumbo 60 includes a drifter 61, a guide cell 62, a drilling rod 63, and a drilling bit 64. The rear end of the drilling rod 63 is connected to the drifter 61. The drifter 61 is configured to supply a rotational force and a striking force to the drilling rod 63. Further, a reinforcing pipe 30 to be driven is arranged in the guide cell 62, and the drilling rod 63 is inserted into the reinforcing pipe 30. The length of the drilling rod 63 is longer than that of the reinforcing pipe 30, and the tip portion of the drilling rod 63 is exposed from the tip of the reinforcing pipe 30. A drilling bit 64 is attached to the tip of the exposed drilling rod 63.

Using this drill jumbo 60, each reinforcing pipe 30 can be driven as follows. That is, the drilling rod 61 is driven with the reinforcing pipe 30 mounted on the drilling rod 63 to supply rotational force and striking force to the drilling rod 63, whereby the drilling rod 63 is mounted on the tip of the drilling rod 63. A hole is formed in the excavation surface 12 by the hole bit 64. Subsequently, after forming a hole having a depth sufficient for driving the reinforcing pipe 30, the hole is drilled through the internal space of the reinforcing pipe 30 while the reinforcing pipe 30 remains in the formed hole. The rod 63 and the drilling bit 64 are pulled out from the drilling. Then, a cement-based, resin-based, water glass-based, or other solidifying material is injected into the reinforcing pipe 30, and the solidifying material is filled in the gap between the reinforcing pipe 30 and the drilled hole and the internal space of the reinforcing pipe 30. do. As a result, each reinforcing pipe 30 can be placed.

[Reinforcing pipe]
Next, an example of each reinforcing pipe 30 that can be used in the above tunnel construction method will be described with reference to FIGS. 8 and 9. FIG. 8 schematically illustrates the reinforcing pipe 30 according to the present embodiment. FIG. 9 is a partial cross-sectional view schematically illustrating the reinforcing pipe 30.

Each reinforcing pipe 30 according to the present embodiment has a plurality of pipe bodies (40, 41) having a length of about 1 m to 3.5 m and having through holes 52 for discharging a solidifying material at a predetermined pitch on the peripheral wall. It is configured by connecting in series so as to have a predetermined total length. The method of connection is a screw joint, welding, or the like. Each first pipe body 40 is arranged on the rear end side of the reinforcing pipe 30, and each second pipe body 41 is arranged on the front end side of the reinforcing pipe 30. Basically, each first pipe body 40 constitutes a first portion 31 to be driven into the first region 13, and each second pipe body 41 is a second portion to be driven into the second region 14. 32 is configured. However, the configuration of the first portion 31 and the second portion 32 of each reinforcing pipe 30 may not be limited to such an example. For example, in the present embodiment, the second portion 32 may include a part of the first tubular body 40 provided with the annular slit 54 described later. As a result, when a part of the second portion 32 is driven into the first region 13 due to a dimensional error or the like, a part of the second portion 32 driven into the first region 13 is easily cut off. Can be made possible.

As shown in FIG. 9, on the outer peripheral surface of the first tubular body 40, recesses 51 extending spirally at predetermined intervals in the axial direction, and annular slits 54 extending one circumference (360 degrees) in the circumferential direction are provided. Is provided. A through hole 52 that penetrates the wall of the first tubular body 40 in the radial direction is provided in the recess 51, and extends in the axial direction between the adjacent annular slits 54 in accordance with the position of the through hole 52. A vertical slit 53 is provided. The second tubular body 41 has a configuration in which the longitudinal slit 53 and the annular slit 54 are omitted from the first tubular body 40. That is, only the recess 51 and the through hole 52 are provided on the outer peripheral surface of the second pipe body 41.

The through hole 52 serves to discharge the consolidated material injected into the reinforcing pipe 30 to the outside of the reinforcing pipe 30, that is, to the ground around the outside of the reinforcing pipe 30 when the auxiliary work installation process is carried out. The solidifying material discharged from the through hole 52 fills the gap between the reinforcing pipe 30 and the drilled hole and spreads to the ground around the reinforcing pipe 30. As a result, the reinforcing pipe 30 is well fixed, and is integrated with the ground into which the binder is injected to stabilize the ground in front of the face and above the excavation cross section.

At this time, since the through hole 52 exists in the recess 51, the through hole 52 is not blocked by the inner wall of the drilled hole, and the solidifying material can be appropriately discharged. Further, even if the reinforcing pipe 30 is in close contact with the inner wall of the drilled hole, the solidifying material discharged from the through hole 52 can spread throughout the drilled hole along the recess 51.

Further, the annular slit 54 is provided so that the first pipe body 40 can be excavated by an excavator or the like during the excavation process. That is, in the above excavation step, a blade of an excavator or the like is inserted into the annular slit 54, and the ground is excavated while excavating the first pipe body 40. Further, the excised first tubular body 40 can be disassembled on a horizontal surface in the axial direction by using the longitudinal slit 53. As a result, the solidifying material solidified in the first tube body 40 and the first tube body 40 can be separated.

The longitudinal slit 53 and the annular slit 54 may be provided in the first pipe body 40 constituting at least the first portion 31 of the reinforcing pipe 30. Further, the number of each of the longitudinal slit 53 and the annular slit 54 may be appropriately determined according to the embodiment, and may be one or a plurality.

The material of each reinforcing pipe 30 having the above-mentioned structure may be appropriately determined according to the embodiment, and for example, a resin material that can be sheared during excavation may be used. Examples of shearable resin materials include fiber reinforced plastics, resin pipes, and the like.

§2 Features As described above, in the tunnel construction method according to the present embodiment, each reinforcing pipe 30 is placed at a position separated from the support work 20 inward in the radial direction and at a predetermined elevation angle with respect to the excavation direction. As a result, the first portion 31 of each reinforcing pipe 30 is driven into the first region 13, and the second portion 32 is driven into the second region 14.

The first region 13 is a ground to be excavated in front of the face 11, and the second region 14 is a ground located above the planned excavation range. Therefore, while the second portion 32 of each reinforcing pipe 30 functions as a pre-receiver for suppressing the collapse of the face 11 from the second region 14, the first portion 31 of each reinforcing pipe 30 is used as the front ground of the face 11. It can function as a mirror reinforcement that enhances the stability of the mountain.

Therefore, according to the present embodiment, since each reinforcing pipe 30 can have two roles of the pre-received work and the mirror reinforcing work, it is not necessary to construct the pre-received work and the mirror reinforcing work separately. The face 11 can be efficiently reinforced at low cost. In addition, as shown in the simulation results of the examples described later, according to the present embodiment, the axial drag of the tunnel 10 can be expressed by each reinforcing pipe 30 toward the extrusion direction of the face 11. The reinforcing effect of the face 11 can be enhanced.

Further, in the present embodiment, the length of each reinforcing pipe 30 is 15500 mm to 18500 mm, the separation distance H is 900 mm to 1300 mm, the elevation angle E is 8 to 12 degrees, and the first portion 31 and the second portion 32 are used. The ratio can be 1: 0.8 to 1: 1.2. As a result, the roles of the pre-receiver and the mirror reinforcement work can be fully exerted in each of the first part 31 and the second part 32, and the stability of the ground in front of the face 11 can be more rationally improved. ..

Further, in the present embodiment, a longitudinal slit 53 and an annular slit 54 are provided in at least the first portion 31 of each reinforcing pipe 30, and a shearable resin material can be used as the material of each reinforcing pipe 30. As a result, after each reinforcing pipe 30 is placed in the auxiliary work installation process, the first portion 31 of each reinforcing pipe 30 can be easily cut when further excavating the ground. Therefore, according to the present embodiment, the workability of the tunnel 10 can be improved.

§3 Modifications Although the embodiments of the present invention have been described in detail above, the above description is merely an example of the present invention in all respects. Needless to say, various improvements and modifications can be made without departing from the scope of the present invention. For example, the following changes can be made. In the following, the same reference numerals will be used for the same components as those in the above embodiment, and the same points as in the above embodiment will be omitted as appropriate. The following modifications can be combined as appropriate.

In the auxiliary work driving process of the above embodiment, each reinforcing pipe 30 is driven by a double pipe drilling method. However, the method of placing each reinforcing pipe 30 does not have to be limited to such an example, and may be appropriately determined according to the embodiment. Further, the configuration of each reinforcing pipe 30 does not have to be limited to the example of the above embodiment. With respect to the configuration of each reinforcing pipe 30, components can be omitted, replaced or added as appropriate according to the embodiment.

Further, in the above embodiment, there is no reinforcing pipe other than the reinforcing pipe 30 placed at a position separated inward in the radial direction from the support work 20. However, the tunnel construction method according to the above embodiment does not have to be limited to such an example. For example, in addition to the reinforcing pipe 30, there may be a reinforcing pipe to be cast as in the conventional case. That is, the above embodiment may be used in combination with conventional fore-piling, further long mirror reinforcement work, and the like. Further, for example, instead of each reinforcing pipe 30, a steel pipe provided with a stabilizer and having a curved shape may be used.

§4 Examples Hereinafter, examples of the present invention will be described. However, the present invention is not limited to the following examples.

FIG. 10 shows a tunnel construction method according to an embodiment. Further, FIG. 11 shows a tunnel construction method according to a comparative example. In the embodiment, the reinforcing pipe is set to be placed by the same method as that of the above embodiment. On the other hand, in the comparative example, the first reinforcing pipe (reinforcing pipe) was set to be driven in the same manner as in the conventional examples shown in FIGS. 1 and 2, and the driving of the second reinforcing pipe was omitted. The parameters of the examples and comparative examples are as follows. The parameters of the comparative example were set based on the standard tunnel construction conditions.

<Parameters of Examples>
-Reinforcing pipe: Steel pipe (outer diameter: 76.3 mm, wall thickness: 4.2 mm)
-Reinforcing pipe length (casting length): 17500 mm (17.5 m)
-Unit volume weight (γ) of reinforcing pipe: 78 kN / m ³
-Reinforcing tube elastic modulus (E): 210000 MPa
・ Cross-sectional area of reinforcing pipe: 0.95 × 10 ^-3 m ²
・ Second moment of inertia of area of reinforcing pipe: 0.62 × 10 ^-6 m ⁴
・ 1 shift length: 6000 mm (6.0 m)
・ Casting pitch (pitch P): 900 mm (0.9 m)
・ Number of castings per shift: 12.5 ・ Separation distance H: 1000 mm (1.0 m)
・ Elevation angle E: 10 degrees ・ Casting range (angle S): 120 degrees

<Parameters of comparative example>
-Reinforcing pipe: Steel pipe (outer diameter: 114.3 mm, wall thickness: 6.0 mm)
-Reinforcing pipe length (casting length): 12500 mm (12.5 m)
-Unit volume weight (γ) of reinforcing pipe: 78 kN / m ³
-Reinforcing tube elastic modulus (E): 210000 MPa
・ Cross-sectional area of reinforcing pipe: 2.04 × 10 ^-3 m ²
・ Second moment of inertia of area of reinforcing pipe: 3.0 × 10 ^-6 m ⁴
・ 1 shift length: 9000 mm (9.0 m)
・ Casting pitch (pitch P): 450 mm (0.45 m)
・ Number of placements per shift: 25 ・ Placement position: Placement of each reinforcing pipe starting from the support work ・ Placement range: 120 degrees

Using analysis software (FLAC3D: Fast Lagrangian Analysis of Continua in 3 Dimensions: manufactured by ITASCA), three-dimensional numerical analysis models of the above examples and comparative examples were created, and the examples and comparative examples were verified.

FIG. 12 shows a conceptual diagram of the calculation process of the analysis software used. The analysis software numerically tracks the mechanical behavior of a continuous three-dimensional body as it approaches a parallel or steady-state plastic flow. The mechanics of an object can be obtained by using the general principle (definition of strain, law of motion) and the constitutive equation (constitutive equation) that defines an ideal object. The whole mathematical representation is a series of differential equations, related mechanical variables (stress, force), and kinematic variables (strain velocity, velocity, acceleration, displacement). The analysis software solves them for individual geometries and properties, given specific boundary conditions, and initial conditions.

In the above examples and comparative examples, the boundary condition is that the ground surface is a free surface and the other surface is a roller boundary. In addition, the parameters of the input physical property values of the ground were set as follows. The analysis was a complete elasto-plastic analysis based on the Mohr-Coulomb fracture criteria. Furthermore, the parameters of sprayed concrete and (steel) support were set as follows.

<Parameters of the ground>
-Unit volume weight (γ): 19 kN / m ³
-Elastic modulus (E): 50MN / m ²
・ Poisson's ratio: 0.35
・ Adhesive strength (C): 10 kN / m ²
・ Internal friction angle (φ): 35 degrees

<Parameters for sprayed concrete + support work>
-Structural element: Curved plate (shell type)
-Elastic modulus (E): 9230 MPa
・ Cross-sectional area: 0.25m ²

Then, considering the influence of the boundary conditions, the first 20m section was excluded from the evaluation as being excavated all at once, and then excavation was repeated every 1m, and the support was installed with a delay of 1m. .. The section where excavation is repeated every 1 m is set to 60 m. Under the above conditions, the displacement distribution, shear strain distribution, and plastic region distribution in the examples and comparative examples were analyzed.

13A to 13C show the simulation results of the displacement amount distribution, the shear strain amount distribution, and the plastic region distribution in the AA cross section of the example. 14A to 14C show the simulation results of the displacement amount distribution, the shear strain amount distribution, and the plastic region distribution in the BB cross section of the example. 15A to 15C show the simulation results of the displacement amount distribution, the shear strain amount distribution, and the plastic region distribution in the CC cross section of the comparative example. 16A to 16C show simulation results of displacement amount distribution, shear strain amount distribution, and plastic region distribution in the DD cross section of the comparative example. In the displacement distribution and the shear strain distribution, the darker the color, the larger the value. Further, in the plastic region distribution, the hatched portion indicates the plastic region, and the white portion indicates the elastic region. As shown in FIGS. 10 and 11, the AA cross section and the CC cross section are set as the cross sections of the excavated surface in which each reinforcing pipe is placed. Further, the BB cross section and the DD cross section were set as the cross sections immediately before each reinforcing pipe was placed.

As shown in the above simulation results, it was found that the effect of suppressing the displacement, strain, and plastic region of the ground in front of the face by the example was higher than that of the comparative example. As a result, according to the present invention, it has been found that the axial drag of the tunnel can be exerted by each reinforcing pipe toward the extrusion direction of the face, and the reinforcing effect of the ground in front of the face can be enhanced.

Further, from FIGS. 15A to 15C and FIGS. 16A to 16C, in the tunnel construction method according to the comparative example, the displacement, strain, and plastic region of the ground in front of the face in the DD cross section immediately before placing each reinforcing pipe. Was confirmed to be larger than the CC cross section in which each reinforcing pipe was placed. On the other hand, from FIGS. 13A to 13C and FIGS. 14A to 14C, in the tunnel construction method according to the embodiment, B- immediately before each reinforcing pipe is placed, as compared with the AA cross section in which each reinforcing pipe is placed. It was confirmed that the displacement, strain, and plastic region of the ground in front of the face in the B section were not so large. In particular, it was confirmed that the plastic region of the BB cross section was smaller than that of the AA cross section. Thereby, according to the present invention, when digging a tunnel, the plasticization of the ground around the tunnel is reduced, so that the open portion of the excavated surface is made smaller and the possibility that the excavated surface collapses is reduced. It turned out that the effect that can be expected can be expected.

10 ... tunnel, 11 ... face, 12 ... excavation surface (mirror surface),
13 ... 1st area, 14 ... 2nd area,
20 ... Support, 21 ... Sprayed concrete,
22 ... Rock bolt, 23 ... Secondary lining concrete,
30 ... Reinforcing pipe, 30A ... (Existing) Reinforcing pipe,
31 ... 1st part, 32 ... 2nd part,
40 ... 1st tube, 41 ... 2nd tube,
51 ... recess, 52 ... through hole, 53 ... longitudinal slit,
54 ... Circular slit,
60 ... Drill jumbo,
61 ... Drifter, 62 ... Guide cell, 63 ... Drilling rod,
64 ... Drilling bit

Claims (4)

By excavating the ground, the steps to dig a tunnel and
In the area where the ground is excavated, a step of installing a support in the circumferential direction of the tunnel from the ceiling surface to both sides of the tunnel, and
A step of placing a plurality of reinforcing pipes at a predetermined interval in the circumferential direction on the excavated surface of the face of the tunnel, and the first excavation schedule located in front of the excavated surface in the excavation direction of the tunnel. Radiation from the support so that each of the plurality of reinforcing pipes has a first portion to be driven into the region and a second portion to be driven into the second region adjacent to the outer side in the radial direction of the first region. A step of placing each of the plurality of reinforcing pipes at a predetermined elevation angle with respect to the excavation direction at positions separated inward in the direction, and
Bei to give a,
The length of each of the plurality of reinforcing pipes in the axial direction is 15500 mm to 18500 mm.
In the step of placing, a drilling rod having a drilling bit attached to the tip thereof is inserted into each of the plurality of reinforcing pipes, and each of the plurality of reinforcing pipes is driven while drilling with the drilling bit. ,
Each of the plurality of reinforcing pipes has an elevation angle of 8 to 12 degrees with respect to the excavation direction at a position 900 mm to 1300 mm inward in the radial direction from the support in order to reinforce the excavation surface by the first portion. And it is placed so that the ratio of the first part to the second part is 1: 0.8 to 1: 1.2.
Tunnel construction method. At least the first portion of each of the plurality of reinforcing pipes is provided with one or a plurality of slits so as to be excised during the excavation.
The tunnel construction method according to claim 1. At least the first portion of each of the plurality of reinforcing pipes is made of a resin material that can be sheared during excavation.
The tunnel construction method according to claim 1 or 2. On the outer peripheral surface of each of the plurality of reinforcing pipes, recesses extending spirally at predetermined intervals in the axial direction are provided.
The recess is provided with a through hole that radially penetrates the wall of the first portion.
The tunnel construction method according to any one of claims 1 to 3.

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