JP7403116B2 - Ground reinforcement method - Google Patents

Description

The present invention relates to a ground reinforcement method.

A mountain construction method called the NATM method (New Austrian Tunneling Method) is known as a construction method for constructing tunnels. The NATM method uses arch-shaped steel supports made of shotcrete, rock bolts, H-shaped steel, etc., based on the idea of effectively utilizing the supporting capacity and strength of the ground to maintain tunnel stability. This is a construction method that, when used appropriately, constructs tunnel structures that are integrated with the ground.

In the NATM construction method, construction is sometimes performed in combination with various ground reinforcement construction methods (auxiliary construction methods) for the purpose of suppressing tunnel face stability and tunnel deformation. For example, in order to prevent the skin from falling off at the top of the tunnel and the ground from falling off, a long injection pipe is driven along the top of the face into the ground diagonally in front of the excavation direction. A long steel pipe advance construction method (AGF construction method) is known in which an injection material is injected from an injection pipe and hardened to consolidate and improve the ground (for example, see Patent Documents 1 to 3).

In addition, if the ground bearing capacity of the tunnel is low and there is a concern that the entire tunnel will sink, steel pipes with higher tensile and shear strength than rock bolts can be driven into the ground laterally from the tunnel side wall. Also known is the side pile construction method, which integrates the steel pipe with the ground by injecting fixing material from inside the pipe.

Patent No. 3919731 Patent No. 4640674 Patent No. 5965778 Patent No. 6430358

However, in the conventional side pile construction method, the steel pipe is installed along the tunnel cross direction perpendicular to the tunnel longitudinal direction (tunnel axial direction), so the displacement of the front ground due to ground excavation is suppressed. However, the effects were not expected to be very high, and there was a risk that the subsidence of the tunnel ground could not be sufficiently suppressed.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide ground reinforcement capable of suppressing tunnel subsidence prior to excavation of the forward ground in the direction of tunnel excavation. The purpose is to provide technology related to construction methods.

The present invention for solving the above problems involves drilling a hole in the ground on the side from the tunnel side wall located near the tunnel face, and inserting a core material for reinforcing the ground into the drilled hole. A ground reinforcement part is formed in the ground by injecting a consolidation material into the borehole, or by inserting a core material for ground reinforcement into the borehole after filling the borehole with consolidation material. The ground reinforcement method is such that the ground drilling angle between the drilling direction for the lateral ground and the tunnel excavation direction is set to be an acute angle, and at least a part of the ground reinforcement section is formed in the ground in front of the face. It is characterized by being formed to extend into a mountain.

Further, in the present invention, the ground reinforcement portion may be formed at a height corresponding to the vicinity of the leg portion of a steel support included in the support structure of the tunnel.

Further, in the present invention, the ground reinforcement portion may be formed for each excavation cycle section in which the ground in front of the face is excavated for a certain section in the tunnel excavation direction.

Further, in the present invention, a set of the ground reinforcement portions may be formed in the ground on the left and right sides of the tunnel for each excavation cycle section.

Further, in the present invention, the ground reinforcement portion in each excavation cycle section may be formed at the same position in a cross-sectional view of the tunnel.

Furthermore, in the present invention, the ground drilling angles of each of the ground reinforcement parts in each excavation cycle section may be equal to each other.

Further, in the present invention, the ground reinforcement portion may include a ground improvement area formed by hardening of the consolidation material injected into the ground around the drilled hole. In this case, a plurality of the ground reinforcement parts may be arranged in succession within the ground so that the ground improvement areas in the ground reinforcement parts are connected. Furthermore, the ground reinforcement section is formed for each excavation cycle section in which a certain section of the ground in front of the face is excavated in the tunnel excavation direction, so that the ground improvement regions of the ground reinforcement sections that are adjacent to each other are connected to each other. The ground reinforcement portion may be formed in each excavation cycle section.

According to the present invention, it is possible to provide a technique related to a ground reinforcement method that can suppress tunnel subsidence prior to excavation of the ground in front of the tunnel in the tunnel excavation direction.

FIG. 1 is a diagram schematically showing a vertical cross section of a tunnel to which the ground reinforcement method according to Embodiment 1 is applied. FIG. 2 is a schematic structural diagram of the earth reinforcement structure according to the first embodiment. FIG. 3 is a schematic structural diagram of the earth reinforcement structure according to the first embodiment. FIG. 4 is a diagram showing the detailed structure of the core material for ground reinforcement according to the first embodiment. FIG. 5 is a diagram illustrating the detailed structure of the injection unit according to the first embodiment. FIG. 6 is a configuration diagram of the injection machine according to the first embodiment. FIG. 7 is a configuration diagram of the mixer according to the first embodiment. FIG. 8 is a diagram showing a state in which a mixer is incorporated into the first inner tube and the second inner tube according to the first embodiment. FIG. 9 is a diagram showing the construction procedure of the earth reinforcement structure according to the first embodiment. FIG. 10 is a diagram showing a situation in which a core material for ground reinforcement is cast into a side ground from a target casting position in a side wall portion in a newly constructed section of a tunnel according to the first embodiment. FIG. 11 is a diagram illustrating a situation in which a set of right and left core materials for ground reinforcement has been completed in a newly constructed section of a tunnel according to the first embodiment. FIG. 12 is a diagram showing a state in which the injection unit according to the first embodiment is attached to a core material for reinforcing the earth. FIG. 13 is a diagram illustrating a ground reinforcement portion formed within the ground. FIG. 14 is a diagram illustrating the reinforcement part center axis pitch of the ground reinforcement part according to the first embodiment. FIG. 15 is a diagram illustrating a ground reinforcement method according to a modification of the first embodiment. FIG. 16 is a schematic structural diagram of the earth reinforcement structure according to the second embodiment. FIG. 17 is a schematic structural diagram of the earth reinforcement structure according to the second embodiment. FIG. 18 is a schematic diagram illustrating a rock reinforcement section according to the second embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

<Embodiment 1>
FIG. 1 is a diagram schematically showing a vertical cross section of a tunnel T to which the ground reinforcement method according to the first embodiment is applied. The tunnel T is a tunnel constructed by, for example, the mountain construction method (NATM construction method). To explain the general procedure in the mountain construction method, after excavating the ground 1 over a certain section (hereinafter referred to as "excavation cycle section") in the tunnel excavation direction DT along the tunnel axis of the tunnel T, To ensure stability and control deformation, support structures such as shotcrete, steel shoring, rock bolts, etc. will be installed. Although the length of the excavation cycle section is not particularly limited, an example in which the excavation cycle section is about 1 m will be described below.

In FIG. 1, 3 is the primary shotcrete layer, 4 is the arch-shaped steel shoring made of H-shaped steel, and 5 is the primary shotcrete layer 3 and the steel shoring 4 integrated. This is the secondary shotcrete layer that is fixed to the concrete. Moreover, the code|symbol 8 is a lock bolt. The steel supports 4 are erected at predetermined intervals, such as every 1 m, in the tunnel excavation direction DT. However, the spacing between the steel supports 4 in the tunnel excavation direction DT is not particularly limited. Further, in FIG. 1, reference numeral 6 is a side wall portion of the tunnel T, and reference numeral 7 is an upper half plate. In the mountain construction method, as described above, the tunnel T is sequentially extended by repeating the excavation of the ground 1 and the installation of the support structure for each excavation cycle section. Note that the ground 1 is earth and sand, bedrock, etc. around the tunnel. Further, the face 2 is the frontmost excavation surface on which the excavation work of the earth 1 is being performed.

In the present embodiment, a ground reinforcement method (auxiliary method) is employed to construct a ground reinforcement structure 10 for reinforcing the ground 1 for the purpose of suppressing subsidence of the tunnel T, restraining the ground in front, and the like. Hereinafter, the rock reinforcement structure 10 in this embodiment will be explained in detail.

2 and 3 are diagrams showing a schematic structure of a rock reinforcement structure 10 according to the rock reinforcement method of the first embodiment. FIG. 2 shows a schematic structure of the rock reinforcement structure 10 in the cross-sectional direction of the tunnel T, and FIG. 3 shows a planar structure of the rock reinforcement structure 10. The cross section of the tunnel T is a cross section perpendicular to the tunnel axis direction (tunnel excavation direction DT). FIG. 3 shows a cross section taken along the line AA in FIG. The symbol CL1 shown in FIG. 3 is the tunnel axis of the tunnel T. In this specification, tunnel axis CL1 extends parallel to tunnel excavation direction DT. Moreover, the broken line shown in FIG. 3 shows the area for each excavation cycle section. Moreover, the code|symbol 1b shown in FIG. 3 is the face front rock located in front of the face 2.

The ground reinforcement method in this embodiment involves drilling a hole from the side wall 6 of the tunnel T to the left and right side ground 1a located on the side of the tunnel T, and inserting a core material 14 for ground reinforcement into the drilled hole. A feature is that a rock reinforcement portion 12 is formed within the side rock 1a by injecting (filling) a consolidating material (fixing material) into the drilled hole in the inserted state.

As shown in FIG. 3, the ground reinforcement parts 12 formed in the side ground 1a are arranged at predetermined intervals (hereinafter referred to as "reinforcement part formation pitch RP") along the tunnel excavation direction DT (tunnel axis CL1 direction). ). In this embodiment, the reinforcement part formation pitch RP corresponds to, for example, the length of one excavation cycle section (for example, about 1 m), and one set of left and right rock reinforcement parts 12 is provided on the side for each excavation cycle section. It is designed to be formed on the ground 1a.

The reference numeral 11L shown in FIG. 3 indicates a plurality of ground reinforcement parts 12 that are arranged in series at a predetermined reinforcement part formation pitch RP in the side ground 1a located on the left side of the tunnel T with respect to the tunnel excavation direction DT. It is an aggregate, and is hereinafter referred to as a rock reinforcement structure 11L. Further, reference numeral 11R denotes an aggregate of a plurality of ground reinforcement parts 12 arranged in succession at a predetermined reinforcement part formation pitch RP in the side ground 1a located on the right side of the tunnel T with respect to the tunnel excavation direction DT. Hereinafter, it will be referred to as a rock reinforcement structure 11R. Note that the reinforcement part formation pitch RP is the interval between the ground reinforcement parts 12 in the direction along the tunnel excavation direction DT.

Each of the mountain reinforcement parts 12 included in the earth reinforcement structure 11L and the earth earth reinforcement structure 11R has the same structure. When the rock reinforcement structure 11L and the rock reinforcement structure 11R are not distinguished, they may be simply referred to as "rock reinforcement structure 11." In this embodiment, the earth reinforcement structure 10 is configured including the earth earth reinforcement structure 11L and the earth earth reinforcement structure 11R.

Moreover, as shown in FIG. 2, the ground reinforcement part 12 extends from the side wall part 6 in the tunnel T (specifically, the secondary shotcrete layer 5 forming the side wall part 6) into the side ground ground 1a. and extends horizontally. Here, the ground reinforcement portions 12 that are consecutively provided for each excavation cycle section are formed at the same position in the cross-sectional view of the tunnel T. Further, the load of the earth 1 is concentrated near the legs of the steel shoring 4. Therefore, it is preferable that the height of the ground reinforcement part 12 constructed on the side ground 1a corresponds to the vicinity of the leg of the steel shoring 4. Further, as shown in FIG. 3, each of the mountain reinforcement parts 12 in the earth reinforcement structure 11 extends into the side earth 1a in an inclined attitude with respect to the tunnel excavation direction DT (tunnel axis CL1 direction). The mountain reinforcing portions 12 are arranged parallel to each other in plan view.

Next, the detailed structure of the ground reinforcement section 12 will be explained. The ground reinforcement part 12 includes a core material 14 for ground reinforcement inserted into a hole (insertion hole) 13 drilled (drilled) in the left and right side ground 1a of the tunnel T, and a core material 14 for ground reinforcement inserted into the hole 13 . A consolidation reinforcing part 16 is formed in the side earth 1a by injecting a consolidation material (anchoring material) 15 into the drilled hole 13 with a core material 14 for reinforcement of the earth inserted therein. It is configured. Details of the consolidation reinforcing portion 16 will be described later.

FIG. 4 is a diagram showing the detailed structure of the core material 14 for ground reinforcement according to the first embodiment. The core material 14 for ground reinforcement is a self-drilling injection type steel rock bolt, and includes a first rock bolt body 141, a second rock bolt body 142, a connecting sleeve 143, a drilling bit 144, a shank sleeve 145, etc. . The first lock bolt body 141 and the second lock bolt body 142 are fully threaded hollow bolts. A hollow portion 140 is formed in the first lock bolt body 141 and the second lock bolt body 142, passing through the first lock bolt body 141 and the second lock bolt body 142 along the bolt axial direction.

Further, threaded portions 141b and 142b are formed on the outer surfaces of the first lock bolt main body 141 and the second lock bolt main body 142 along the bolt axial direction. In addition, discharge ports 141c and 142c that penetrate the first lock bolt body 141 and the second lock bolt body 142 in the plate thickness direction are opened at the tip sides of the first lock bolt body 141 and the second lock bolt body 142. There is. Each discharge port 141c, 142c in the first rock bolt body 141 and the second rock bolt body 142 discharges the consolidating material (fixing material) 15 injected into the hollow part 140 to the first rock bolt body 141 and the second rock bolt body 142. This is an opening for discharging to the outside of the main body 142. For example, the discharge ports 141c and 142c in the first lock bolt main body 141 and the second lock bolt main body 142 are opened at a plurality of locations along the circumferential direction of the bolt at approximately equal intervals. However, the number, position, etc. of each discharge port 141c, 142c in the first lock bolt main body 141 and the second lock bolt main body 142 can be changed as appropriate.

The connection sleeve 143 is a tubular member made of steel that connects the rear end of the first lock bolt body 141 and the tip of the second lock bolt body 142. A threaded portion (not shown) that can be screwed onto the threaded portions 141b and 142b of the first lock bolt main body 141 and the second lock bolt main body 142 is formed on the inner peripheral side of the connection sleeve 143. The first lock bolt body 141 and the second lock bolt body 142 are integrally connected via a connecting sleeve 143 with the rear end of the first lock bolt body 141 and the tip of the second rock bolt body 142 butting together. .

The shank sleeve 145 is an adapter member for detachably attaching the rear end side of the core material 14 for ground reinforcement (second rock bolt main body 142) to an attachment of a hydraulic drifter (rock drill). A first joint portion 145a is provided on the distal end side of the shank sleeve 145, and a second joint portion 145b is provided on the rear end side. The first joint portion 145a of the shank sleeve 145 is a cylindrical member to which the second lock bolt body 142 is detachably connected by receiving the rear end side of the second lock bolt body 142. It has an inner circumferential surface formed with a threaded portion (not shown) that can be screwed into the threaded portion 142b. Further, the second joint portion 145b of the shank sleeve 145 is a cylindrical member that can be detachably attached to the attachment of the hydraulic drifter.

The drilling bit 144 is a bit member for drilling a hole in the earth 1, and is attached to the tip of the first rock bolt body 141. The drilling bit 144 has a discharge hole 144a that discharges drilling water, and can drill a hole in the ground while jetting the drilling water from the discharge hole 144a.

The core material 14 for ground reinforcement configured as described above is cast into the side ground 1a and then penetrates the first rock bolt body 141 and the second rock bolt body 142 by the injection unit 17. A consolidation material (fixing material) 15 is injected into the hollow portion 140 . Details of the injection unit 17 will be described below. Note that the core material 14 for ground reinforcement shown in FIG. 4 connects the first rock bolt body 141 and the second rock bolt body 142 via the connection sleeve 143, but it is not possible to connect a plurality of bolts in this way. Instead of this embodiment, the drilling bit 144 may be attached to the front end side of a single bolt, and the shank sleeve 145 may be attached to the rear end side.

FIG. 5 is a diagram illustrating the detailed structure of the injection unit 17 according to the first embodiment. The injection unit 17 includes a first inner tube 171, a second inner tube 172, a mounting adapter 173, and the like. The first inner tube 171 and the second inner tube 172 are formed of a hollow pressure-resistant hose or a pressure-resistant tube member, and a flow path P1 through which the consolidation material 15 flows is formed along the tube axial direction. . The first inner tube 171 and the second inner tube 172 are fixed together in a mutually bundled state by a suitable fixing member 174.

A closing member 175 that closes the flow path P1 is provided at the distal end of the first inner tube 171 and the second inner tube 172, respectively. A mixer 18 is provided within the flow path P1. The mixer 18 will be described later. As shown in FIG. 5, the first inner tube 171 and the second inner tube 172 are fixed together by a fixing member 174 such that the distal end of the first inner tube 171 is located forward of the distal end of the second inner tube 172. ing. The amount of positional deviation in the tube axial direction between the tip of the first inner tube 171 and the tip of the second inner tube 172 is the bolt axis between the discharge port 141c of the first lock bolt body 141 and the discharge port 142c of the second rock bolt body 142. This roughly matches the amount of positional deviation in the direction. Further, an injection adapter 177 for injecting the consolidation material 15 into each flow path P1 of the first inner tube 171 and the second inner tube 172 is attached to the rear end of the first inner tube 171 and the second inner tube 172. It is being

Moreover, the attachment adapter 173 is a cylindrical adapter member for detachably attaching the injection unit 17 to the rear end of the earth reinforcement core material 14 (second rock bolt main body 142). The mounting adapter 173 has an inner peripheral surface formed with a threaded portion 173a that can be screwed onto the threaded portion 142b of the second lock bolt body 142. Furthermore, a check valve 178 is provided inside the mounting adapter 173 to prevent the consolidation material 15 injected into the flow path P1 of the first inner tube 171 and the second inner tube 172 from flowing backward. There is.

FIG. 6 is a configuration diagram of the injection machine 19 for pumping the consolidation material 15 to the first inner tube 171 and the second inner tube 172 according to the first embodiment. The injection machine 19 includes a first pumping unit 191 that pumps the consolidation material 15 to the first inner tube 171 and a second pumping unit 192 that pumps the consolidation material 15 to the second inner tube 172. The first pressure feeding unit 191 and the second pressure feeding unit 192 have substantially the same configuration.

The first pressure feeding unit 191 and the second pressure feeding unit 192 have a first tank 193 that stores liquid A of the consolidation material 15 and a second tank 194 that stores liquid B of the consolidation material 15. Reference numeral 195 is a mixing unit that mixes liquid A and liquid B of the consolidation material 15. Reference numeral 196A is a first pressure pump, and reference numeral 196B is a second pressure pump. Reference numeral 197A is a first delivery hose, and reference numeral 197B is a second delivery hose. The first delivery hose 197A is a pressure-resistant hose that connects the first tank 193 and the mixing unit 195. The second delivery hose 197B is a pressure-resistant hose that connects the second tank 194 and the mixing unit 195. By operating the first pressure pump 196A, liquid A of the consolidation material 15 stored in the first tank 193 is sent to the mixing unit 195 through the first delivery hose 197A. Furthermore, by operating the second pressure pump 196B, liquid B of the consolidation material 15 stored in the second tank 194 is sent to the mixing unit 195 through the second delivery hose 197B.

The A liquid and the B liquid of the consolidation material 15 that have joined together in the mixing unit 195 are mixed by the mixing unit 195. The mixing unit 195 of the first pressure feeding unit 191 is connected to the injection adapter 177 of the first inner tube 171 through the third delivery hose 197C, and the caking material 15 in a state where the two liquids are mixed is transferred to the third delivery hose 197C. is fed to the first inner tube 171 under pressure. Similarly, the mixing unit 195 of the second pressure feeding unit 192 is connected to the injection adapter 177 of the second inner tube 172 through the third delivery hose 197C, and the solidifying material 15 in a state where the two liquids are mixed is transferred to the third delivery hose 197C. It is force-fed to the second inner tube 172 by the delivery hose 197C. Further, a pressure gauge 198 is provided in the first delivery hose 197A of the first pressure feeding unit 191 and the second pressure feeding unit 192.

FIG. 7 is a configuration diagram of the mixer 18 provided at the distal ends of the first inner tube 171 and the second inner tube 172 according to the first embodiment. FIG. 8 is a diagram showing a state in which the mixer 18 is incorporated into the first inner tube 171 and the second inner tube 172 according to the first embodiment. The mixer 18 includes a shaft portion 181 extending in a straight line, a stirring blade portion 182 spirally formed around the shaft portion 181, a washer plate 183 provided on the rear end side of the mixer 18, and the like. . The washer plate 183 of the mixer 18 has a disk shape. Furthermore, a communication hole 183a is provided in the center of the plane of the washer plate 183 so as to pass through the washer plate 183. D1 shown in FIG. 7 indicates the outer diameter of the washer plate 183 in the mixer 18. The outer diameter D1 of the washer plate 183 is equal to the inner diameters of the first inner tube 171 and the second inner tube 172.

In FIG. 8, the mixer 18 is inserted from the distal end sides of the first inner tube 171 and the second inner tube 172, and the side surface of the washer plate 183 is attached to the inner peripheral surfaces 171a and 172a of the first inner tube 171 and the second inner tube 172. The state in which the distal ends of the first inner tube 171 and the second inner tube 172 are closed by the closing member 175 after being fitted and fixed is shown. By fitting the washer plate 183 to the inner peripheral surfaces 171a and 172a of the first inner tube 171 and the second inner tube 172, the central axis of the shaft portion 181 is coaxial with the central axis of the first inner tube 171 and the second inner tube 172. It will be placed in the state.

Further, the first inner tube 171 and the second inner tube 172 are connected in the thickness direction of the first inner tube 171 and the second inner tube 172 at positions corresponding to the distal ends of the first inner tube 171 and the second inner tube 172, specifically, to the distal ends of the mixer 18. Communication holes 171b and 172b penetrating through are provided. The consolidation material 15 that has flowed into the flow path P1 from the injection adapter 177 in the first inner tube 171 is pumped toward the mixer 18. Then, the solidified material 15 that has sequentially passed through the communication hole 183a formed in the washer plate 183 of the mixer 18 and the stirring blade part 182 is transferred from the communication hole 171b of the first inner tube 171 to the outside, that is, to the first lock bolt body 141. It flows out into the hollow part 140. Similarly, the consolidation material 15 that has flowed into the flow path P1 from the injection adapter 177 in the second inner tube 172 is pumped toward the mixer 18. Then, the solidified material 15 that has sequentially passed through the communication hole 183a formed in the washer plate 183 of the mixer 18 and the stirring blade part 182 is transferred from the communication hole 172b of the second inner tube 172 to the outside, that is, to the second lock bolt body 142. It flows out into the hollow part 140. Further, in the first inner tube 171 and the second inner tube 172 in this embodiment, since the mixer 18 is provided in the distal end region of the flow path P1, when the solidified material 15 passes through the stirring blade part 182, The consolidation material 15 can be suitably stirred.

Next, the construction procedure of the ground reinforcement structure 10 according to the ground reinforcement method will be explained. FIG. 9 is a diagram showing a construction procedure of the rock reinforcement structure 10 according to the first embodiment. In constructing the earth reinforcement structure 10, preparatory work is first performed in step S101. When the preparation work in step S101 is completed, pouring work is performed in step S102. Further, when the pouring process in step S102 is completed, a pouring process is performed in step S103. Further, when the injection process in step S103 is completed, a rear end spraying process is performed in step S104. The specific contents of each step will be explained below.

In the preparatory work (step S101), secondary shotcrete is sprayed in the newly constructed section of the tunnel T to form a secondary shotcrete layer 5 (see FIG. 1). In addition, in the preparation work (step S101), the placement position (hereinafter referred to as "target placement position PT") of a set of core materials 14 for ground reinforcement to be newly placed in the newly constructed section of the tunnel T is determined. A survey is conducted and the target placement position PT of the core material 14 for ground reinforcement is marked on the side wall 6 of the tunnel T (the surface of the secondary shotcrete layer 5 constituting the side wall 6) (see Fig. 1). . The height of the target casting position PT is set to a height corresponding to the vicinity of the legs of the steel shoring 4, and for example, it is set to a position that is a predetermined dimension higher than the base plate position of the steel shoring 4. It's okay.

In addition, the target casting position PT in the new section is the reinforcement part in the tunnel excavation direction DT (tunnel axis CL1 direction) from the target casting position PT of the core material 14 for ground reinforcement cast in the previous excavation cycle section. It is set at a position forward by a forming pitch RP. In addition, when forming the secondary shotcrete layer 5 in the newly constructed section of the tunnel T during preparatory work, the secondary shotcrete layer 5 is applied in a certain range R (hereinafter referred to as "core material placement surrounding area") including the target placement position PT. The thickness of the concrete layer 5 is made thinner than the specified thickness.

Next, the core material 14 for ground reinforcement is moved into the side ground 1a from the target placement position PT marked on the side wall 6 (the surface of the secondary shotcrete layer 5 constituting the side wall 6) in the tunnel T. to be poured. In the existing section located on the rear side of the new section, the plurality of ground reinforcement parts 12 in the ground reinforcement structures 11L and 11R have already been formed at the reinforcement part formation pitch RP.

FIG. 10 is a diagram showing a situation in which the core material 14 for ground reinforcement is cast into the side ground 1a from the target casting position PT in the side wall 6 in the newly constructed section of the tunnel T according to the first embodiment. The core material 14 for ground reinforcement is placed while the shank sleeve 145 of the core material 14 for ground reinforcement explained in FIG. 4 is held by an attachment of a drifter mounted on heavy machinery such as a drill jumbo. . The ground reinforcing core material 14 may be placed using a drifter while rotating the ground reinforcing core material 14 and striking the shank sleeve 145.

Here, the core material 14 for ground reinforcement is cast in a straight line from the target casting position PT on the side wall 6 of the tunnel T toward the "earth drilling direction Db" shown in FIG. The rock drilling direction Db is set such that the angle θ1 (hereinafter referred to as "rock drilling angle") formed by the rock drilling direction Db and the tunnel excavation direction DT (tunnel axis CL1) is an acute angle. ing. FIG. 10 illustrates a case where the ground drilling angle θ1 is set to 45°. Further, the core material 14 for reinforcing the ground is placed horizontally into the side ground 1a from the target placement position PT on the side wall 6 of the tunnel T. In addition, since the primary shotcrete layer 3 and the secondary shotcrete layer 5 are formed inside the side ground 1a, the ground reinforcement core material 14 penetrates each concrete layer. It is poured into the side ground 1a.

FIG. 11 is a diagram illustrating a situation in which a pair of left and right core materials 14 for ground reinforcement have been completely cast in a newly constructed section of the tunnel T according to the first embodiment. In addition, although FIG. 10 illustrates the situation in which the core material 14 for ground reinforcement is placed on the right side ground 1a of the tunnel T, the ground reinforcing core material 14 is similarly placed on the left side ground 1a. The core material 14 for reinforcing the ground is placed so that the hole drilling angle θ1 becomes an acute angle (45° in this case).

Here, since the core material 14 for ground reinforcement is formed by a self-drilling injection type steel rock bolt, the core material 14 for ground reinforcement 14 is inserted into the side ground 1a from the side wall portion 6 of the tunnel T. By casting, the formation of the drill hole 13 in the side ground 1a and the insertion of the core material 14 for ground reinforcement into the drill hole 13 are performed at the same time. In the present embodiment, the ground drilling angle θ1 formed by the ground drilling direction Db of the ground reinforcement core material 14 and the tunnel excavation direction DT (tunnel axis CL1) is set to an acute angle, thereby reinforcing the ground. A core material 14 (drilled hole 13) is arranged to extend diagonally forward from the side wall portion 6 of the tunnel T toward the face front ground 1b. Thereby, at least a part of the core material 14 for ground reinforcement (boring hole 13) including the tip side can be made to reach the ground in front of the face 1b and extend to the ground in front of the face 1b.

After the installation of the right and left sets of core materials 14 for ground reinforcement in the newly constructed section of the tunnel T is completed, injection work is performed in the following step S103. Here, the shank sleeve 145 is removed from the rear end of the ground reinforcing core material 14, and the injection unit 17 described in FIG. 5 is attached to the ground reinforcing core material 14. Specifically, the first inner tube 171 and the second inner tube 172 in the injection unit 17 are inserted into the hollow part 140 from the rear end of the second rock bolt body 142 in the core material 14 for ground reinforcement, and A mounting adapter 173 is attached to the rear end of the reinforcing core material 14 (second lock bolt body 142).

FIG. 12 is a diagram showing a state in which the injection unit 17 according to the first embodiment is attached to the core material 14 for reinforcing the earth. In this embodiment, by attaching the mounting adapter 173 to the rear end of the core material 14 for ground reinforcement (second rock bolt main body 142), the The first inner tube 171 and the second inner tube 172 are automatically positioned. As a result, the positions of the communication hole 171b (see FIG. 8) of the first inner tube 171 and the discharge port 141c (see FIG. 4) of the first lock bolt body 141 are aligned in the bolt axial direction of the first lock bolt body 141. It is possible to roughly match along the lines. Similarly, the positions of the communication hole 172b (see FIG. 8) of the second inner tube 172 and the discharge port 142c (see FIG. 4) of the second lock bolt body 142 are adjusted in the bolt axial direction of the second lock bolt body 142. It is possible to roughly match along the lines.

After the injection unit 17 is attached to the core material 14 for ground reinforcement as described above, each third delivery hose 197 of the first pressure feeding unit 191 and the second pressure feeding unit 192 in the injection machine 19 is connected to the first inner tube. 171 and the second inner tube 172 to the injection adapter 177 . This completes the preparation for pumping the consolidation material 15 into the hollow part 140 of the core material 14 for ground reinforcement using the injection machine 19 and the injection unit 17.

Thereafter, when the first pressure pump 196A and the second pressure pump 196B in the injection machine 19 are operated, the consolidation material 15 pressure-fed from the first pressure-feeding unit 191 and the second pressure-feeding unit 192 is transferred to the first inner tube 171 and the second pressure-feeding pump 196B. The liquid flows from each injection adapter 177 of the two inner tubes 172 into the flow path P1. The solidified material 15 supplied into each flow path P1 is sufficiently stirred when passing through the stirring blade portion 182 of the mixer 18 disposed at the tip side of each flow path P1. The consolidated material 15 sufficiently obtained in the mixer 18 is transferred to the hollow part 140 of the earth reinforcement core material 14 through the communication holes 171b and 172b formed at the tips of the first inner tube 171 and the second inner tube 172. and leaks out.

The consolidation material 15 that has flowed out from the communication hole 171b of the first inner tube 171 into the hollow part 140 of the first lock bolt body 141 is filled so as to fill the space of the hollow part 140 of the first rock bolt body 141, and It is discharged to the outside of the first lock bolt body 141 from the discharge port 141c of the first lock bolt body 141. Further, the solidifying material 15 flowing out from the communication hole 172b of the second inner tube 172 fills the space in the hollow part 140 in the second rock bolt body 142, and also fills the space at the discharge port of the second rock bolt body 142. 142c and is smoothly discharged to the outside of the second lock bolt body 142.

Here, since the mutual positions of the communication hole 171b of the first inner tube 171 and the discharge port 141c of the first lock bolt body 141 generally match, the solidified material 15 flowing out from the communication hole 171b of the first inner tube 171 can be smoothly discharged from the discharge port 141c of the first lock bolt main body 141 to the outside. Similarly, since the mutual positions of the communication hole 172b of the second inner tube 172 and the discharge port 142c of the second lock bolt body 142 generally match, the solidified material 15 flowing out from the communication hole 172b of the second inner tube 172 can be smoothly discharged to the outside from the discharge port 142c of the second lock bolt main body 142.

Note that the discharge ports 141c of the first lock bolt body 141 may be provided at a portion other than the tip of the first lock bolt body 141, and are provided at regular intervals along the bolt axial direction of the first lock bolt body 141. They may be arranged. Similarly, the discharge port 142c of the second lock bolt body 142 may be provided at a location other than the tip of the second rock bolt body 142, and may be provided at regular intervals along the bolt axial direction of the second rock bolt body 142. It may be arranged in Further, since the drilling bit 144 of the first rock bolt main body 141 has a discharge hole 144a, the consolidation material 15 can also be discharged into the drilling hole 13 from the discharge hole 144a.

As described above, the consolidation material 15 discharged at a predetermined pressure from each discharge port 141c, 142c in the core material 14 for ground reinforcement (first rock bolt body 141, second rock bolt body 142) is It is filled into the gap formed between the core material 13 and the core material 14 for reinforcing the rock, and is injected and permeated into the surrounding ground existing around (around) the core material 14 for rock reinforcement. As a result, as shown in FIG. 13, the consolidation material 15 filled in the gap between the drilled hole 13 and the core material 14 for reinforcing the ground hardens to form a fixation area 16a, and is injected into the surrounding ground. The ground improvement region 16b is formed by hardening the solidified material 15. Here, the fixing area 16a is an area where the core material 14 for reinforcing the ground and the surrounding ground are fixed together. Moreover, the ground improvement area 16b is an area where the surrounding ground has been consolidated and improved. In the earth reinforcement structure 10 of this embodiment, the consolidation reinforcement part 16 of the earth reinforcement part 12 is comprised including the anchoring area 16a and the earth improvement area 16b.

In the injection work, when it is confirmed that the preset amount of consolidation material 15 has been injected, the operation of the first pressure pump 196A and the second pressure pump 196B is stopped, and the consolidation material 15 is injected. Finish the injection work. The injection speed of the consolidation material 15 by the injection machine 19 is not particularly limited, but may be, for example, about 5 kg/min. In addition, in the injection work, an inflatable rubber packer or the like may be installed on the rear end side of the core material 14 for ground reinforcement, and by inflating the rubber packer at the same time as the consolidation material 15 is injected, consolidation can be achieved. You may suppress that the material 15 leaks from the rear end side of the core material 14 for ground reinforcement. In addition, the injection amount of the consolidation material 15 supplied from the injection machine 19 in the injection work is determined by the volume of the hollow part of the core material 14 for ground reinforcement, and the amount formed between the drilled hole 13 and the core material 14 for ground reinforcement. It can be set based on the volume of the fixing area 16a, the volume of the ground improvement area 16b where the ground is consolidated and improved, etc. Further, a mixer 18 is provided on the distal end side of the first inner tube 171 and the second inner tube 172 in this embodiment, and the solidifying material 15 can be sufficiently mixed and stirred in the stirring blade part 182 of the mixer 18. can. In this way, by mixing and stirring the consolidation material 15 at a position immediately before injection into the ground, it is possible to prevent the consolidation material 15 from clogging the hollow portion 140 of the core material 14 for ground reinforcement. can.

When the injection work of the consolidation material 15 is completed, a rear end spraying process is performed in step S104. In the rear end spraying process, shotcrete is sprayed onto a region R around the core material placement in the side wall portion 6 of the tunnel T. Note that the first inner tube 171 and the second inner tube 172 may be cut at the rear end position of the mounting adapter 173 prior to spraying the shotcrete to the core material placement peripheral region R. After that, shotcrete is applied to the area R around where the core material is placed so that the mounting adapter 173 of the core material 14 for ground reinforcement exposed in the area R around where the core material is placed on the side wall 6 of the tunnel T is buried. Spray to the specified thickness. When the rear end spraying process described above is completed, a pair of left and right rock reinforcement sections 12 are constructed for the newly constructed section of the tunnel T, as shown in FIGS. 2 and 3. After newly constructing the pair of left and right rock reinforcement sections 12 in the newly constructed section in this way, the rock excavation for the next excavation cycle section is performed. In this embodiment, by alternately repeating the construction of the support structure and the ground reinforcement structure 10 for the newly constructed section in each excavation cycle section, the subsidence of the side ground 1a is suppressed while the ground in front of the face is strengthened. Reinforcement can be applied before excavation.

As described above, in the ground reinforcement method in this embodiment, when driving the ground reinforcement core material 14 from the side wall part 6 of the tunnel T to the side ground 1a, the ground drilling direction Db and the tunnel The ground drilling angle θ1 with the excavation direction DT is set to an acute angle, and the ground reinforcement part 12 constructed in the new section is moved from the side wall part 6 of the tunnel T to the ground in front of the face 1b located in front of the face 2. It is arranged so that it extends diagonally forward. According to this, at least a part (in this embodiment, most part as shown in FIG. 3) of the earth reinforcement part 12 can be made to extend to the face front earth 1b. As a result, before excavating the ground in front of the face 1b in the next excavation cycle section, the ground in front of the face is 1b can be reinforced in advance. As a result, the restraining force of the ground in front of the face 1b in the tunnel T is increased, and it is possible to suitably suppress the tunnel T from sinking when excavating the ground in front of the face 1b.

Furthermore, according to the ground reinforcement method in this embodiment, a set of ground reinforcement parts 12 are formed on the left and right side ground 1a of the tunnel T for each excavation cycle section, so The mountain 1a can be suitably reinforced.

In addition, in the ground reinforcement method in this embodiment, the ground reinforcement part 12 is formed horizontally from the side wall part 6 of the tunnel T into the side ground 1a, so that the subsidence of the tunnel is preferably prevented. can be suppressed to Furthermore, in this embodiment, as shown in FIG. 3, the ground reinforcement part 12 is formed so as to cross the slip line of the side ground 1a, so that the side ground 1a becomes loose. This can be suitably suppressed. Further, in the ground reinforcement method according to the present embodiment, the height of the ground reinforcement part 12 formed in the ground 1 is made to correspond to the vicinity of the leg of the steel shoring 4. By constructing the ground reinforcing portion 12 at a height near the legs of the steel shoring 4 where the load of the ground 1 is concentrated in this way, it is possible to suppress subsidence of the tunnel even more suitably. However, in the ground reinforcement method of this embodiment, it is sufficient to form the ground reinforcement part 12 in the ground 1 from the side wall part 6 of the tunnel T, and the ground reinforcement part 12 constructed in the ground 1 is not necessarily It is not necessary to correspond to the vicinity of the legs of the steel shoring 4.

Moreover, in the ground reinforcement method in this embodiment, the ground reinforcement part 12 is formed for each excavation cycle section in which the ground in front of the face 1b is excavated for a certain section in the tunnel excavation direction DT. According to this, the reinforcing portions can be successively provided on the side ground 1a of the tunnel T along the tunnel excavation direction DT at every reinforcing portion formation pitch RP. According to this, the rock reinforcement structure 11, which is an aggregate of the rock reinforcement parts 12 arranged in series in the tunnel excavation direction DT, becomes strong, and a larger rock load is supported by the rock reinforcement structure 11. Therefore, the subsidence of the tunnel T can be suppressed more suitably.

In particular, in this embodiment, since the rock drilling angle θ1 formed by the rock drilling direction Db and the tunnel excavation direction DT is set to an acute angle, the rock drilling direction Db is set in a direction orthogonal to the tunnel digging direction DT. (i.e., when the core material 14 for ground reinforcement is placed in a direction perpendicular to the tunnel excavation direction DT), the center axis of the adjacent ground reinforcement part 12 in the side ground 1a is The interval W1 between them (hereinafter referred to as "reinforcement part center axis pitch") can be made small.

Here, FIG. 14 is a diagram illustrating the reinforcing part central axis pitch W1 of the ground reinforcing part 12 according to the first embodiment. The symbol CL2 in FIG. 14 is the central axis of the earth reinforcement part 12. Here, the central axis CL2 of the earth reinforcement part 12 can also be said to be the central axis of the earth earth reinforcement core material 14. Moreover, the central axis CL2 of the earth reinforcement part 12 is parallel to the earth excavation direction Db. Moreover, the reinforcement part central axis pitch W1 refers to the interval between the central axes CL2 of the rock reinforcement part 12 in the direction orthogonal to the central axis CL2 of the rock reinforcement part 12. Further, FIG. 14 also shows an example in which the ground drilling angle θ1 between the ground drilling direction Db and the tunnel excavation direction DT is set to 45°. Moreover, illustration of the drilled hole 13 is omitted in FIG. 14.

In this embodiment, since the ground drilling angle θ1 is an acute angle, the reinforcement part center axis pitch W1 is smaller than the reinforcement part formation pitch RP, as shown in FIG. In the example shown in FIG. 14, since the ground drilling angle θ1 is 45°, the reinforcement part center axis pitch W1 is 1/√2 times (approximately 0.7 times) the reinforcement part formation pitch RP. On the other hand, when the ground drilling angle θ1 is set to a right angle (when the ground reinforcing core material 14 is cast in a direction perpendicular to the tunnel excavation direction DT), the central axis CL2 of the ground reinforcing part 12 is perpendicular to the tunnel excavation direction DT, so the reinforcement part center axis pitch W1 of the ground reinforcement part 12 becomes equal to the reinforcement part formation pitch RP.

Therefore, as in the present embodiment, by making the ground drilling angle θ1 acute, the reinforcement part center axis pitch W1 (center axis interval of the ground reinforcement core material 14) of the ground reinforcement part 12 can be adjusted to It can be narrower than the formation pitch RP. As a result, if the injection amount of the consolidating material 15 in the above-mentioned injection method is the same, the distance W2 between the adjacent ground reinforcing parts 12 in the ground 1 will also be perpendicular to the ground drilling angle θ1. This can be made smaller than in the case where the core material 14 for reinforcing the ground is placed in a direction perpendicular to the tunnel excavation direction DT. That is, the width of the unreinforced area of the ground located between the ground reinforcing parts 12 can be narrowed. Thereby, the planar rock reinforcement structure 11 can be constructed within the rock 1 by the densely arranged rock reinforcement parts 12, and the reinforcing effect of the rock 1 becomes extremely excellent. Therefore, according to the earth reinforcement structure 11 in this embodiment, a larger earth load can be supported, and the subsidence of the tunnel T can be suitably suppressed.

In addition, in the ground reinforcement method according to Embodiment 1, the ground reinforcement parts are arranged so that the consolidated reinforcement parts 16 (ground improvement areas 16b) of the ground reinforcement parts 12 that are adjacent to each other in the ground reinforcement structure 11 are connected to each other. 12 may be formed. By doing so, it is possible to construct a planar rock reinforcement structure 11 in which the rock reinforcement parts 12 included in the rock reinforcement structure 11 are integrated, and the reinforcement effect of the rock becomes extremely excellent. In addition, in order to make the ground improvement regions 16b in the ground reinforcement parts 12 adjacent to each other continuous as described above, the ground drilling angle θ1, the reinforcement part formation pitch RP, and the injection amount of the consolidation material 15 in the injection work are required. This can be achieved by adjusting etc.

Furthermore, in the ground reinforcement method in this embodiment, the ground reinforcement portions 12 in each excavation cycle section are formed at the same position in the cross-sectional view of the tunnel T. According to this, the ground reinforcement parts 12 in each excavation cycle section can be arranged even more densely. As a result, the effect of reinforcing the ground 1 can be further enhanced. In addition, in this embodiment, the ground reinforcement part 12 in each excavation cycle section is extended and arranged in the horizontal direction, but it is not restricted to this. For example, each of the rock reinforcement parts 12 may be constructed so that the angle of elevation or depression of the rock reinforcement parts 12 in each excavation cycle section is equal to each other.

Further, according to the ground reinforcement method in this embodiment, the ground drilling angles θ1 of the ground reinforcement parts 12 in each excavation cycle section are equal to each other. According to this, when the core material 14 for ground reinforcement is poured into the side ground 1a in the new section, the core material 14 for ground reinforcement may interfere with the existing ground reinforcement part 12, or Damage to the ground reinforcement part 12 can be suppressed.

In this embodiment, the ground drilling angle θ1 when pouring the ground reinforcement core material 14 into the side ground 1a may be an acute angle, and is not limited to a specific angle, but may be from 30° to Preferably, the angle is set within a range of 60°. Here, when the total length of the core material 14 for ground reinforcement is equal, the smaller the ground drilling angle θ1 is, the longer the casting length in the tunnel excavation direction, which is the length of the core material 14 for ground reinforcement 14 in the tunnel excavation direction DT. While a large length L2 can be ensured, the transverse casting length L3, which is the casting length of the core material 14 for ground reinforcement in the tunnel transverse direction, becomes small. Conversely, the larger the ground drilling angle θ1, the smaller the driving length L2 in the tunnel excavation direction DT of the core material 14 for ground reinforcement. It is possible to ensure a large transverse direction casting length L3, which is the casting length in the tunnel transverse direction at No. 14. The larger the casting length L2 in the excavation direction is, the more the range in which the rock face in front of the face 1b can be reinforced can be expanded when constructing the rock reinforcement part 12 in the newly constructed section. Therefore, we set a transverse casting length L3 that allows the ground reinforcement part 12 to cross the slip line of the side ground 1a, and make the ground drilling angle θ1 as small as possible within such a range. It may also be set at an angle. Thereby, it is possible to maximize the reinforcement amount and reinforcement range of the face front ground 1b while suppressing the subsidence of the side ground 1a. In addition, in this embodiment, the rock drilling angle θ1 of each rock reinforcement part 12 in the rock reinforcement structure 11L and the reinforcement part extension angle θ1 of each rock reinforcement part 12 in the rock reinforcement structure 11R are set to different angles. You can also set it.

Further, the base material of the core material 14 for ground reinforcement in this embodiment preferably has a yield strength of 400 kN/piece or more, a breaking strength of 600 kN/piece or more, and a shear strength of 200 kN/piece or more. By using such a high-rigidity, high-strength core material 14 for ground reinforcement, it is possible to secure the same or higher rigidity and strength as steel pipes commonly used as side piles, while also reducing the ground strength compared to using steel pipes. The time required for pouring into mountains can be significantly reduced. As a result, workability can be improved and construction costs can be reduced. Moreover, according to the core material 14 for reinforcing the ground in this embodiment, the time required for placing the core material into the ground can be shortened, so that the effects of drilling water and vibration on the ground can be reduced. For example, KAT-R51 (manufactured by Katex Corporation) made of S45C carbon steel for machine structures can be suitably used as the core material 14 for reinforcing the ground. KAT-R51 has an outer diameter of approximately 50 mm, a wall thickness of approximately 8 mm, and a weight of approximately 8.5 kg/m, making it extremely lightweight compared to steel pipes commonly used as side piles, reducing construction time and reducing construction time. Workability can be improved.

Further, the type of the consolidation material 15 is not particularly limited, and a cement-based consolidation material or a urethane-based consolidation material may be selected as appropriate depending on the condition of the ground or spring water, for example. In addition, it is preferable to use a urethane-based solidifying material, which has superior properties such as higher strength, faster hardening and strength development after hardening, and easier penetration into the voids in the ground compared to cement-based solidifying materials. be.

<Modified example>
Various changes can be made to the ground reinforcement method in this embodiment. For example, as shown in FIG. 15, the ground reinforcing portions 12 may be arranged in multiple stages in the height direction of the side ground 1a. By doing so, the effect of reinforcing the ground can be further enhanced. In the example shown in FIG. 15, the ground reinforcement portions 12 are arranged in two stages in the same cross section of the tunnel, but they may be arranged in three or more stages. Further, in the first embodiment, a case where a self-drilling type hollow lock bolt is used as the core material 14 for reinforcing the ground has been described as an example, but an insertion type hollow lock bolt may also be used. In this case, after drilling a hole in the side ground 1a, a hollow rock bolt is inserted into the drilled hole 13. Then, with the hollow rock bolt inserted into the drilled hole 13, the consolidation material 15 is injected into the drilled hole 13 using the above-mentioned injection unit 17 and injection machine 19, thereby forming the ground reinforcement part 12. Can be done.

Further, the core material 14 for reinforcing the ground applied to the present invention is not limited to an injection type hollow rock bolt. For example, a solid rock bolt may be used as the core material for reinforcing the ground. In this case, a hole is formed in the side ground 1a from the side wall part 6 in the newly constructed section located near the face 2 of the tunnel T, and after filling the hole with a consolidating material as a fixing material, A ground reinforcement portion may be formed within the ground by inserting a solid rock bolt into the ground. Embodiment 2 will be described below.

<Embodiment 2>
16 and 17 are schematic structural diagrams of a ground reinforcement structure 10A constructed by the ground reinforcement method according to the second embodiment. FIG. 16 shows a schematic structure of the rock reinforcement structure 10A in the cross-sectional direction of the tunnel T, and FIG. 17 shows a planar structure of the rock reinforcement structure 10A. Detailed explanations will be omitted by using the same reference numerals for members, structures, terms, etc. that are common to those in Embodiment 1.

The ground reinforcement structure 10A includes a ground reinforcement structure 11L built on the left side ground 1a of the tunnel T and a ground reinforcement structure 11R built on the right side ground 1a. ing. The ground reinforcement structures 11L and 11R are aggregates of ground reinforcement parts 12A connected for each excavation cycle section. The ground reinforcement structure 10A in this embodiment is the same as that in the first embodiment except that the structure of the ground reinforcement part 12A is different from the ground reinforcement part 12 according to the first embodiment.

FIG. 18 is a schematic diagram illustrating a rock reinforcement section 12A according to the second embodiment. The ground reinforcement part 12A includes a drilled hole 13 formed in the side ground 1a, a core material 14A for ground reinforcement inserted into the drilled hole 13, and a consolidation material 15 filled in the drilled hole 13. It includes a solidified reinforcing portion 16A formed by hardening. For example, the ground reinforcement section 12A, like the ground reinforcement section 12 of the first embodiment, constructs a support structure in the newly constructed section of the tunnel T, then performs the preparatory work described in FIG. A hole is drilled into the side ground 1a from the target casting position PT. Drilling into the side rock 1a can be performed using a hydraulic drifter or the like, and the hole 13 is formed along the rock drilling direction Db as in the first embodiment. Also in this embodiment, the ground drilling angle θ1 formed by the ground drilling direction Db and the tunnel excavation direction DT (tunnel axis CL1) is set to be an acute angle. Therefore, at least a part of the drilled hole 13 extending diagonally forward from the side wall 6 of the tunnel T toward the ground in front of the face 1b reaches the ground in front of the face 1b and extends into the ground in front of the face 1b. There will be.

Next, after filling the drilled hole 13 with a predetermined amount of consolidation material (fixing material) 15, the core material 14A for reinforcing the ground is inserted into the drilled hole 13. In this embodiment, a solid fully threaded lock bolt is used as the core material 14A for ground reinforcement, but the lock bolt to be used is not particularly limited. Moreover, the core material 14A for reinforcing the ground may be formed by connecting a plurality of bolts. Further, the consolidation material (fixing material) 15 is not particularly limited, but may be a cement-based consolidation material (fixing material). After curing the consolidation material 15, a washer 147, a bell washer (not shown), etc. are installed on the rear end side of the core material 14A for ground reinforcement, and a nut 148 is fixed with a torque wrench, etc., thereby reinforcing the ground. Construction of section 12A is completed. By hardening the consolidation material 15 filled in the borehole 13, a consolidation reinforcement part 16A is formed, and the consolidation reinforcement part 16A connects the surrounding ground of the borehole 13 (core material 14A for ground reinforcement). The mountain reinforcing core material 14A is fixed.

Thereby, as shown in FIG. 17, the ground reinforcement part 12A formed in the ground so that at least a part thereof extends to the ground in front of the face 1b can be newly installed in the newly constructed section of the tunnel T. As a result, before excavating the ground in front of the face 1b in the next excavation cycle section, the ground in front of the face is 1b can be reinforced in advance. As a result, the restraining force of the ground in front of the face 1b in the tunnel T is increased, and it is possible to suitably suppress the tunnel T from sinking when excavating the ground in front of the face 1b.

The embodiments and modified examples of the ground reinforcement method according to the present invention have been described above, but the present invention is not limited to the above-described embodiments and modified examples, and can be modified as appropriate without departing from the spirit thereof. . For example, in the above-described embodiments and modifications, an example has been described in which the method is applied to construction of the upper half of a tunnel, but the ground reinforcement method according to the present invention may also be applied to construction of the lower half of a tunnel.

T... Tunnel 1... Earth 2... Face 3... Primary shotcrete layer 4... Steel shoring 5... Secondary shotcrete layer 6... Side wall portion 10 ...Mound reinforcement structure 11 ...Mound reinforcement structure 12 ...Mound reinforcement part 13 ...Drilling hole 14 ...Mound reinforcement core material 15 ...Consolidation material 16 ...・Consolidation reinforcement part

Claims (9)

A hole is drilled horizontally and diagonally forward in the ground from the side wall of the tunnel located near the tunnel face, and a core material for reinforcing the ground is inserted into the drilled hole. Ground reinforcement in which a ground reinforcement part is formed within the ground by injecting a compacting material into the ground, or by inserting a ground reinforcing core material into the drilled hole after filling the compacting material into the drilled hole. It is a construction method,
The rock reinforcement part extends horizontally from the tunnel side wall part into the rock on the side, and has a shape defined by a direction of drilling into the rock on the side and a tunnel excavation direction in a plan view of the tunnel. The ground drilling angle is set to an acute angle, and at least a part of the ground reinforcement part is formed to extend to the ground in front of the face.
Ground reinforcement method. The ground reinforcement part is formed at a height corresponding to the vicinity of the leg of the steel support included in the support structure of the tunnel.
The ground reinforcement method according to claim 1. The ground reinforcement part is formed for each excavation cycle section in which a certain section of the ground in front of the face is excavated in the tunnel excavation direction.
The ground reinforcement method according to claim 1 or 2. A set of the ground reinforcement portions is formed in the ground on the left and right sides of the tunnel for each excavation cycle section.
The ground reinforcement method according to claim 3. The ground reinforcement portion in each excavation cycle section is formed at the same position in a cross-sectional view of the tunnel.
The ground reinforcement method according to claim 3 or 4. In each of the ground reinforcement parts in each excavation cycle section, the ground drilling angle is equal to each other;
The ground reinforcement method according to any one of claims 3 to 5. The ground reinforcement portion includes a ground improvement area formed by hardening of the consolidation material injected into the ground surrounding the drilled hole.
The ground reinforcement method according to any one of claims 1 to 6. arranging a plurality of ground reinforcement parts in a row in the ground so that the ground improvement areas in the ground reinforcement parts are connected;
The ground reinforcement method according to claim 7. The ground reinforcement part is formed for each excavation cycle section in which a certain section of the ground in front of the face is excavated in the tunnel excavation direction,
forming the rock reinforcement portion in each excavation cycle section so that the rock improvement regions of the rock reinforcement portions that are adjacent to each other are connected;
The ground reinforcement method according to claim 8.

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