JP2021025330A - Natural ground reinforcing method - Google Patents

Abstract

To provide technology related to a natural ground reinforcement method that can suppress subsidence of a tunnel prior to the excavation of the front natural ground in a tunnel excavation direction.SOLUTION: A natural ground reinforcement method that a drilling hole is drilled in the natural ground on the side from the side wall of a tunnel located near the cutting face of the tunnel, a core material for reinforcing the natural ground is injected into the drilling hole, a solidification material is injected in the drilling hole, or a core material for reinforcing the natural ground is injected into the drilling hole after filling the drilling hole with the solidification material, and a natural ground reinforcement part in the natural ground is formed, comprising : in the natural ground reinforcement part, a natural ground drilling angle between a drilling direction and a tunnel excavation direction with respect to the natural ground on the side is set to an acute angle, at least part of the natural ground is formed so as to extend to the natural ground in front of the cutting face.SELECTED DRAWING: Figure 3

Description

The present invention relates to a ground reinforcement method.

As a construction method for constructing a tunnel, a mountain construction method called the NATM construction method (New Austrian Tunneling Method) is known. The NATM method is based on the idea of maintaining the stability of the tunnel by effectively utilizing the support capacity and strength of the ground, and arch-shaped steel support made of sprayed concrete, rock bolts, H-shaped steel, etc. It is a construction method to construct a tunnel structure integrated with the ground by using it as appropriate.

In the NATM construction method, it may be constructed in combination with various ground reinforcement construction methods (auxiliary construction methods) for the purpose of suppressing the stability of the face and the deformation of the tunnel. For example, for the purpose of preventing the skin from falling off at the top of the tunnel and the peeling of the ground, a long injection pipe is placed along the top of the face in the ground diagonally forward in the digging direction. A long steel pipe tip receiving method (AGF method) is known in which an injection material is injected from an injection pipe and hardened to solidify and improve the ground (see, for example, Patent Documents 1 to 3).

In addition, if the ground bearing capacity of the tunnel is small and there is concern about the sinking of the entire tunnel, a steel pipe with higher tensile strength and shear strength than the rock bolt is placed in the ground from the side wall of the tunnel toward the side. A side pile method is also known in which the ground and the steel pipe are integrated by injecting a fixing material from the inside of the steel pipe.

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

However, in the conventional side pile method, since the steel pipe is placed along the tunnel crossing direction orthogonal to the tunnel longitudinal direction (tunnel axial direction), the displacement of the front ground due to the ground excavation is suppressed. The effect could not be expected so much, 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 problems, and an object of the present invention is to reinforce the ground capable of suppressing the subsidence of the tunnel prior to the excavation of the front ground in the tunnel excavation direction. The purpose is to provide technology related to construction methods.

In the present invention for solving the above problems, a hole is drilled in the ground on the side from the side wall of the tunnel located near the face of the tunnel, and a core material for reinforcing the ground is inserted in the hole. A ground reinforcing portion is formed in the ground by injecting a solidifying material into the drilled hole or filling the drilling material with the solidifying material and then inserting a core material for ground reinforcement into the drilled hole. It is a ground reinforcement method, and in the ground reinforcement part, the ground drilling angle formed by the drilling direction and the tunnel excavation direction with respect to the lateral ground is set to a sharp angle, and at least a part of the ground is in front of the face. It is characterized by being formed so as to extend to the mountains.

Further, in the present invention, the ground reinforcement portion may be formed at a height corresponding to the vicinity of the leg portion of the steel support work 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 for excavating the ground in front of the face for a certain section in the tunnel excavation direction.

Further, in the present invention, a set of the ground reinforcing portions may be formed on the left and right grounds 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 the cross-sectional view of the tunnel.

Further, in the present invention, each of the ground reinforcing portions in each excavation cycle section may have the same ground drilling angle.

Further, in the present invention, the ground reinforcement portion may include a ground improvement region formed by hardening the solidifying material injected into the ground around the hole. In this case, a plurality of the ground reinforcement portions may be continuously provided in the ground so that the ground improvement areas in the ground reinforcement portion are connected. Further, the ground reinforcement portion is 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, so that the ground improvement areas of the ground reinforcement portions adjacent to each other are connected to each other. The ground reinforcement portion may be formed in each excavation cycle section.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a technique relating to a ground reinforcement method capable of suppressing subsidence of a tunnel prior to excavation of the front ground 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 the first embodiment is applied. FIG. 2 is a schematic structural diagram of the ground reinforcement structure according to the first embodiment. FIG. 3 is a schematic structural diagram of the ground reinforcement structure according to the first embodiment. FIG. 4 is a diagram showing a detailed structure of the core material for reinforcing the ground according to the first embodiment. FIG. 5 is a diagram illustrating a 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 block diagram of the mixer according to the first embodiment. FIG. 8 is a diagram showing a state in which the mixer is incorporated in the first inner tube and the second inner tube according to the first embodiment. FIG. 9 is a diagram showing a construction procedure of the ground reinforcement structure according to the first embodiment. FIG. 10 is a diagram showing a situation in which a core material for reinforcing the ground is placed on the lateral ground from the target placement position on the side wall portion in the new section of the tunnel according to the first embodiment. FIG. 11 is a diagram showing a situation in which a pair of left and right ground reinforcing core materials have been placed in the new section of the 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 the core material for reinforcing the ground. FIG. 13 is a diagram illustrating a ground reinforcement portion formed in the ground. FIG. 14 is a diagram for explaining the central axis pitch of the reinforcing portion of the ground reinforcing portion according to the first embodiment. FIG. 15 is a diagram illustrating a ground reinforcement method according to a modified example of the first embodiment. FIG. 16 is a schematic structural diagram of the ground reinforcement structure according to the second embodiment. FIG. 17 is a schematic structural diagram of the ground reinforcement structure according to the second embodiment. FIG. 18 is a schematic view illustrating a ground reinforcement portion according to the second embodiment.

Hereinafter, embodiments of the present invention will be described 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, for example, a tunnel constructed by a 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 "drilling cycle section") in the tunnel excavation direction DT along the tunnel axis of the tunnel T, the face 2 Support structures such as sprayed concrete, steel support, lock bolts, etc. will be installed to ensure stability and suppress deformation. The length of the excavation cycle section is not particularly limited, but the case where the excavation cycle section is about 1 m will be described below as an example.

In FIG. 1, reference numeral 3 is a primary sprayed concrete layer, reference numeral 4 is an arch-shaped steel support formed of H-shaped steel, and reference numeral 5 is a combination of a primary sprayed concrete layer 3 and a steel support 4. It is a secondary sprayed concrete layer to be fixed to. Reference numeral 8 is a lock bolt. The steel support 4 is built in the tunnel excavation direction DT at predetermined intervals such as every 1 m. However, the building interval of the steel support 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 board. In the mountain construction method, 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 as described above. The ground 1 is earth and sand, bedrock, etc. around the tunnel. Further, the face 2 is the frontmost excavated surface where the excavation work of the ground 1 is performed.

In the present embodiment, a ground reinforcement method (auxiliary method) for constructing a ground reinforcement structure 10 for reinforcing the ground 1 is adopted for the purpose of suppressing the settlement of the tunnel T and restraining the front ground. Hereinafter, the ground reinforcement structure 10 in the present embodiment will be described in detail.

2 and 3 are diagrams showing a schematic structure of the ground reinforcement structure 10 according to the ground reinforcement method of the first embodiment. FIG. 2 shows a schematic structure of the ground reinforcement structure 10 in the cross-sectional direction of the tunnel T, and FIG. 3 shows a planar structure of the ground reinforcement structure 10. The cross section of the tunnel T is a cross section orthogonal to the tunnel axial direction (tunnel excavation direction DT). FIG. 3 shows a cross section taken along the line AA in FIG. Reference numeral CL1 shown in FIG. 3 is a tunnel axis of the tunnel T. In the present specification, the tunnel axis CL1 extends parallel to the tunnel excavation direction DT. The broken line shown in FIG. 3 indicates a region for each excavation cycle section. Further, reference numeral 1b shown in FIG. 3 is a face front ground located in front of the face 2.

In the ground reinforcement method in the present embodiment, holes are drilled in the left and right lateral grounds 1a located on the side of the tunnel T from the side wall portion 6 of the tunnel T, and the ground reinforcement core material 14 is formed in the drilled holes. It is characterized in that a ground reinforcing portion 12 is formed in the lateral ground 1a by injecting (filling) a solidifying material (fixing material) into the drilled hole in the inserted state.

As shown in FIG. 3, the ground reinforcing portions 12 formed in the lateral ground 1a are provided at predetermined intervals (hereinafter, referred to as “reinforcing portion forming pitch RP”) along the tunnel excavation direction DT (tunnel axis CL1 direction). ) It is connected every time. In the present embodiment, the reinforcing portion forming pitch RP corresponds to, for example, the length of one excavation cycle section (for example, about 1 m), and one pair of left and right ground reinforcing portions 12 is lateral to each excavation cycle section. It is designed to be formed on the ground 1a.

Reference numeral 11L shown in FIG. 3 refers to a plurality of ground reinforcing portions 12 serially provided by a predetermined reinforcing portion forming pitch RP in the lateral ground 1a located on the left side of the tunnel T with reference to the tunnel excavation direction DT. It is an aggregate, and will be referred to as a ground reinforcement structure 11L below. Further, reference numeral 11R is an aggregate of a plurality of ground reinforcing portions 12 continuously provided by a predetermined reinforcing portion forming pitch RP in the lateral ground 1a located on the right side of the tunnel T with reference to the tunnel excavation direction DT. In the following, it will be referred to as the ground reinforcement structure 11R. The reinforcing portion forming pitch RP is the distance between the ground reinforcing portions 12 in the direction along the tunnel excavation direction DT.

The ground reinforcement structure 11L and each mountain reinforcement portion 12 included in the ground reinforcement structure 11R have the same structure. When the ground reinforcement structure 11L and the ground reinforcement structure 11R are not distinguished, it may be simply referred to as "ground reinforcement structure 11". In the present embodiment, the ground reinforcement structure 10 is configured by including the ground reinforcement structure 11L and the ground reinforcement structure 11R.

Further, as shown in FIG. 2, the ground reinforcing portion 12 enters the lateral ground 1a from the side wall portion 6 (specifically, the secondary sprayed concrete layer 5 constituting the side wall portion 6) in the tunnel T. It is extended in the horizontal direction. Here, the ground reinforcing portions 12 that are continuously 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 ground 1 is concentrated in the vicinity of the legs of the steel support work 4. Therefore, it is preferable that the height of the ground reinforcing portion 12 to be constructed on the lateral ground 1a corresponds to the vicinity of the legs of the steel support work 4. Further, as shown in FIG. 3, the mountain reinforcement portions 12 in the ground reinforcement structure 11 extend into the lateral ground 1a in an inclined posture with respect to the tunnel excavation direction DT (tunnel axis CL1 direction). In addition, the mountain reinforcing portions 12 are arranged parallel to each other in a plan view.

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

FIG. 4 is a diagram showing a detailed structure of the ground reinforcing core material 14 according to the first embodiment. The ground reinforcing core material 14 is a self-drilling injection type steel lock bolt, and has a first lock bolt body 141, a second lock bolt body 142, a connection sleeve 143, a drilling bit 144, a shank sleeve 145, and the like. .. The first lock bolt body 141 and the second lock bolt body 142 are all-screw hollow bolts. The first lock bolt body 141 and the second lock bolt body 142 are formed with a hollow portion 140 that penetrates the first lock bolt body 141 and the second lock bolt body 142 along the bolt axis direction.

Further, screw 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 axis direction. Further, 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 on the tip side of the first lock bolt body 141 and the second lock bolt body 142. There is. The discharge ports 141c and 142c of the first lock bolt main body 141 and the second lock bolt main body 142 have the solidifying material (fixing material) 15 injected into the hollow portion 140 of the first lock bolt main body 141 and the second lock bolt. It is an opening for discharging to the outside of the main body 142. For example, the discharge ports 141c and 142c of the first lock bolt body 141 and the second lock bolt body 142 are opened at a plurality of locations along the bolt circumferential direction at substantially equal intervals. However, the number, position, and the like of the discharge ports 141c and 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 steel tubular member that connects the rear end of the first lock bolt body 141 and the tip of the second lock bolt body 142. On the inner peripheral side of the connection sleeve 143, screw portions (not shown) that can be screwed to the screw portions 141b and 142b of the first lock bolt main body 141 and the second lock bolt main body 142 are formed. The first lock bolt body 141 and the second lock bolt body 142 are integrally connected via the connection sleeve 143 in a state where the rear end of the first lock bolt body 141 and the tip of the second lock bolt body 142 are butted against each other. ..

The shank sleeve 145 is an adapter member for detachably attaching the rear end side of the ground reinforcing core material 14 (second lock bolt main body 142) to the attachment of the hydraulic drifter (rock drill). A first joint portion 145a is provided on the tip 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 tubular member to which the second lock bolt body 142 is detachably connected by accepting the rear end side of the second lock bolt body 142, and the second lock bolt body 142. It has an inner peripheral surface in which a screw portion (not shown) that can be screwed is formed on the screw portion 142b of the above. Further, the second joint portion 145b of the shank sleeve 145 is a tubular 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 ground 1, and is attached to the tip of the first lock bolt main body 141. The drilling bit 144 has a discharge hole 144a for discharging the drilled water, and can drill a ground while injecting the drilled water from the discharge hole 144a.

After being placed in the lateral ground 1a, the ground reinforcement core material 14 configured as described above penetrates the first lock bolt main body 141 and the second lock bolt main body 142 by the injection unit 17. The binder (fixing material) 15 is injected into the hollow portion 140. The details of the injection unit 17 will be described below. The ground reinforcing core material 14 shown in FIG. 4 connects the first lock bolt main body 141 and the second lock bolt main body 142 via the connection sleeve 143, and connects a plurality of bolts in this way. Instead of the embodiment, the drilling bit 144 may be attached to the tip 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 a detailed structure of the injection unit 17 according to the first embodiment. The injection unit 17 includes a first inner tube 171 and 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 by a hollow pressure-resistant hose, a pressure-resistant tube member, or the like, and a flow passage P1 through which the binder 15 flows is formed along the tube axial direction. .. The first inner tube 171 and the second inner tube 172 are integrally fixed in a state of being bundled with each other by an appropriate fixing member 174.

Closing members 175 that block the flow passage P1 are provided at the tips of the first inner tube 171 and the second inner tube 172, respectively, and are located after the closing members 175 in the first inner tube 171 and the second inner tube 172. Is provided with a mixer 18 in the flow passage 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 integrally fixed by the fixing member 174 so that the tip of the first inner tube 171 is located in front of the tip of the second inner tube 172. ing. The amount of misalignment between the tip of the first inner tube 171 and the tip of the second inner tube 172 in the tube axis direction is the bolt shaft of the discharge port 141c of the first lock bolt body 141 and the discharge port 142c of the second lock bolt body 142. It is almost the same as the amount of misalignment in the direction. Further, at the rear ends of the first inner tube 171 and the second inner tube 172, an injection adapter 177 for injecting the binder 15 into each flow passage P1 of the first inner tube 171 and the second inner tube 172 is attached. Has been done.

Further, the mounting adapter 173 is a tubular adapter member for detachably mounting the injection unit 17 to the rear end of the ground reinforcing core member 14 (second lock bolt main body 142). The mounting adapter 173 has an inner peripheral surface on which a screw portion 173a that can be screwed is formed on the screw portion 142b of the second lock bolt main body 142. Further, inside the mounting adapter 173, a check valve 178 for suppressing the backflow of the binder 15 injected into the flow passage P1 of the first inner tube 171 and the second inner tube 172 is provided. There is.

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

The first consolidation unit 191 and the second consolidation unit 192 have a first tank 193 for storing the A liquid of the consolidation material 15 and a second tank 194 for storing the B liquid of the consolidation material 15. Reference numeral 195 is a mixing unit that mixes the liquid A and the liquid B of the binder 15. Reference numeral 196A is a first pump, and reference numeral 196B is a second 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 pump 196A, the liquid A of the binder 15 stored in the first tank 193 is sent to the mixing unit 195 through the first delivery hose 197A. Further, by operating the second pump 196B, the liquid B of the binder 15 stored in the second tank 194 is sent to the mixing unit 195 through the second delivery hose 197B.

The liquids A and B of the binder 15 merged in the mixing unit 195 are mixed by the mixing unit 195. The mixing unit 195 of the first pumping unit 191 is connected to the injection adapter 177 of the first inner tube 171 through the third delivery hose 197C, and the binder 15 in a state where the two liquids are mixed is the third delivery hose 197C. Is pumped to the first inner tube 171. Similarly, the mixing unit 195 of the second pumping unit 192 is connected to the injection adapter 177 of the second inner tube 172 through the third delivery hose 197C, and the binder 15 in a state where the two liquids are mixed is the third. It is consolidated into the second inner tube 172 by the delivery hose 197C. Further, a pressure gauge 198 is provided on the first delivery hose 197A in the first pumping unit 191 and the second pumping unit 192.

FIG. 7 is a configuration diagram of a mixer 18 provided at the tip 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 in 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. Further, a communication hole 183a is provided in the central portion of the plane of the washer plate 183 so as to penetrate 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 diameter of the first inner tube 171 and the second inner tube 172.

In FIG. 8, the mixer 18 is inserted from the tip side of the first inner tube 171 and the second inner tube 172, and the side surface of the washer plate 183 is formed on the inner peripheral surfaces 171a and 172a of the first inner tube 171 and the second inner tube 172. After fitting and fixing, the tip of the first inner tube 171 and the second inner tube 172 is closed by the closing member 175. Due to the fitting of 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 axes of the first inner tube 171 and the second inner tube 172. It will be in the state of being placed in.

Further, at a position corresponding to the tip side of the first inner tube 171 and the second inner tube 172, specifically, the tip side of the mixer 18, the first inner tube 171 and the second inner tube 172 are placed in the member thickness direction. Communication holes 171b and 172b are provided through the holes. The binder 15 that has flowed into the flow passage P1 from the injection adapter 177 in the first inner tube 171 is pumped toward the mixer 18. Then, the solidifying material 15 that has passed through the communication holes 183a formed in the washer plate 183 of the mixer 18 and the stirring blade portion 182 in that order is external from the communication holes 171b of the first inner tube 171, that is, the first lock bolt body 141. It flows out to the hollow portion 140. Similarly, the binder 15 that has flowed into the flow passage P1 from the injection adapter 177 in the second inner tube 172 is pumped toward the mixer 18. The binder 15 that has passed through the communication holes 183a formed in the washer plate 183 of the mixer 18 and the stirring blade portion 182 in that order is external from the communication holes 172b of the second inner tube 172, that is, the second lock bolt body 142. It flows out to the hollow portion 140. Further, in the first inner tube 171 and the second inner tube 172 in the present embodiment, since the mixer 18 is provided in the tip region of the flow passage P1, when the binder 15 passes through the stirring blade portion 182, The binder 15 can be suitably stirred.

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

The preparatory work (step S101) sprays the secondary sprayed concrete in the new section of the tunnel T to form the secondary sprayed concrete layer 5 (see FIG. 1). Further, in the preparatory work (step S101), the placement position of the set of ground reinforcing core material 14 to be newly placed in the new section of the tunnel T (hereinafter referred to as “target placement position PT”). A survey is performed, and the target placement position PT of the ground reinforcing core material 14 is marked on the side wall portion 6 (the surface of the secondary sprayed concrete layer 5 constituting the side wall portion 6) in the tunnel T (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 support 4, for example, set to a position higher than the base plate position in the steel support 4. You may.

Further, the target placement position PT in the new section is a reinforcing portion in the tunnel excavation direction DT (tunnel axis CL1 direction) from the target placement position PT of the ground reinforcement core material 14 placed in the previous excavation cycle section. Only the formation pitch RP is set to the front position. Further, when the secondary sprayed concrete layer 5 is formed in the new section of the tunnel T in the preparatory work, the secondary spraying is performed in a certain range (hereinafter referred to as “core material casting peripheral area”) R including the target casting position PT. The thickness of the attached concrete layer 5 is made thinner than the specified thickness.

Next, the core material 14 for reinforcing the ground from the target casting position PT marked on the side wall portion 6 (the surface of the secondary sprayed concrete layer 5 constituting the side wall portion 6) in the tunnel T into the lateral ground 1a. To place. In the existing section located on the rear side of the new section, a plurality of ground reinforcing portions 12 in the ground reinforcing structures 11L and 11R are already formed by the reinforcing portion forming pitch RP.

FIG. 10 is a diagram showing a situation in which a core material 14 for reinforcing the ground is driven into the lateral ground 1a from the target placement position PT on the side wall portion 6 in the new section of the tunnel T according to the first embodiment. The ground reinforcing core material 14 is placed in a state where the shank sleeve 145 of the ground reinforcing core material 14 described with reference to FIG. 4 is gripped by an attachment of a drifter mounted on a heavy machine such as a drill jumbo. .. The driving of the ground reinforcing core material 14 using the drifter may be performed while rotating the ground reinforcing core material 14 and striking the shank sleeve 145.

Here, the ground reinforcing core material 14 is driven linearly from the target placement position PT in the side wall portion 6 of the tunnel T toward the “ground drilling direction Db” shown in FIG. The ground drilling direction Db is set so that the angle (hereinafter referred to as “ground drilling angle”) θ1 formed by the ground 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 ground reinforcing core material 14 is horizontally driven into the lateral ground 1a from the target placement position PT in the side wall portion 6 of the tunnel T. Since the primary sprayed concrete layer 3 and the secondary sprayed concrete layer 5 are formed inside the lateral ground 1a, the ground reinforcing core material 14 penetrates each concrete layer. It is driven to the side ground 1a.

FIG. 11 is a diagram showing a situation in which a pair of left and right ground reinforcing core members 14 have been placed in the new section of the tunnel T according to the first embodiment. In addition, in FIG. 10, the situation where the core material 14 for reinforcing the ground is placed on the right side ground 1a in the tunnel T is illustrated, but similarly, the ground is also ground on the left side ground 1a. The ground reinforcing core material 14 is placed so that the mountain drilling angle θ1 is an acute angle (here, 45 °).

Here, since the ground reinforcement core material 14 is formed by a self-drilling injection type steel lock bolt, the ground reinforcement core material 14 is formed in the lateral ground 1a from the side wall portion 6 in the tunnel T. By driving, the formation of the drilling hole 13 in the lateral ground 1a and the insertion of the ground reinforcing core material 14 into the drilling hole 13 are performed at the same time. In the present embodiment, the ground reinforcement 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 to reinforce the ground. The core material 14 (drilling hole 13) is arranged so as to extend diagonally forward from the side wall portion 6 of the tunnel T toward the front ground 1b of the face. As a result, at least a part including the tip end side of the ground reinforcing core material 14 (drilling hole 13) can reach the face front ground 1b and extend to the face front ground 1b.

After the placement of the left and right set of the core material 14 for reinforcing the ground is completed in the new section of the tunnel T, the 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 with reference to FIG. 5 is attached to the ground reinforcing core material 14. Specifically, the first inner tube 171 and the second inner tube 172 of the injection unit 17 are inserted into the hollow portion 140 from the rear end of the second lock bolt main body 142 of the ground reinforcing core material 14, and the ground is ground. The mounting adapter 173 is attached to the rear end of the reinforcing core member 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 ground. In the present embodiment, by attaching the mounting adapter 173 to the rear end of the ground reinforcing core material 14 (second lock bolt main body 142), the first is inserted into the hollow portion 140 of the ground reinforcing core material 14. The 1 inner tube 171 and the 2nd 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 moved in the bolt axis direction of the first lock bolt body 141. It can be roughly matched along. 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 positioned in the bolt axis direction of the second lock bolt body 142. It can be roughly matched along.

After the injection unit 17 is attached to the core material 14 for reinforcing the ground as described above, the third delivery hoses 197 of the first pumping unit 191 and the second pumping unit 192 in the injection machine 19 are respectively attached to the first inner tube. It connects to the injection adapter 177 of 171 and the second inner tube 172. As a result, the preparation for pumping the solidifying material 15 to the hollow portion 140 of the core material 14 for reinforcing the ground using the injection machine 19 and the injection unit 17 is completed.

After that, when the first pumping pump 196A and the second pumping pump 196B in the injection machine 19 are operated, the binder 15 pumped from the first pumping unit 191 and the second pumping unit 192 becomes the first inner tube 171 and the first. 2 It flows into the flow passage P1 from each injection adapter 177 of the inner tube 172. The binder 15 supplied into each flow passage P1 is sufficiently agitated when passing through the stirring blade portion 182 of the mixer 18 arranged on the tip side of each flow passage P1. The solidifying material 15 sufficiently satisfied in the mixer 18 as described above is transferred from the communication holes 171b and 172b formed at the tips of the first inner tube 171 and the second inner tube 172 to the hollow portion 140 of the ground reinforcing core material 14. And leak.

The binder 15 flowing out from the communication hole 171b of the first inner tube 171 to the hollow portion 140 of the first lock bolt main body 141 is filled so as to fill the space of the hollow portion 140 in the first lock bolt main body 141, and is also filled. It is discharged from the discharge port 141c of the first lock bolt main body 141 to the outside of the first lock bolt main body 141. Further, the binder 15 flowing out of the communication hole 172b of the second inner tube 172 is filled so as to fill the space of the hollow portion 140 in the second lock bolt main body 142, and the discharge port of the second lock bolt main body 142. It is smoothly discharged from 142c to the outside of the second lock bolt main 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 main body 141 are substantially the same, the binder 15 flowing out from the communication hole 171b of the first inner tube 171. Can be smoothly discharged to the outside from the discharge port 141c of the first lock bolt main body 141. 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 main body 142 are substantially the same, the binder 15 that has flowed 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.

The discharge port 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 may be provided at regular intervals along the bolt axis direction of the first lock bolt body 141. It may be arranged. Similarly, the discharge port 142c of the second lock bolt main body 142 may be provided at a portion other than the tip of the second lock bolt main body 142 at regular intervals along the bolt axial direction of the second lock bolt main body 142. It may be arranged in. Further, since the drilling bit 144 of the first lock bolt main body 141 has a discharge hole 144a, the solidifying material 15 can be discharged into the drilling hole 13 from the discharge hole 144a.

As described above, the solidifying material 15 discharged at a predetermined pressure from the discharge ports 141c and 142c of the ground reinforcing core material 14 (first lock bolt main body 141, second lock bolt main body 142) is drilled. It is filled in the gap formed between the 13 and the ground reinforcing core material 14, and is injected and permeated into the surrounding ground existing around (periphery) the ground reinforcing core material 14. As a result, as shown in FIG. 13, the fixing region 16a is formed by hardening the solidifying material 15 filled in the gap between the drilled hole 13 and the ground reinforcing core material 14, and is injected into the surrounding ground. The ground improvement region 16b is formed by hardening the solidifying material 15. Here, the fixing region 16a is a region for integrally fixing the ground reinforcing core material 14 and the surrounding ground. Further, the ground improvement area 16b is an area where the surrounding ground is consolidated and improved. In the ground reinforcement structure 10 of the present embodiment, the consolidation reinforcement portion 16 of the ground reinforcement portion 12 includes a fixing region 16a and a ground improvement region 16b.

In the injection work, when it is confirmed that the preset amount of the consolidation material 15 has been injected, the operations of the first consolidation pump 196A and the second consolidation pump 196B are stopped, and the consolidation material 15 Finish the injection work. The injection speed of the binder 15 by the injection machine 19 is not particularly limited, and an example in which the injection speed is set to about 5 kg / min can be exemplified. In the injection work, an inflatable rubber packer or the like may be installed on the rear end side of the ground reinforcing core material 14, and the rubber packer is expanded at the same time as the solidifying material 15 is injected to consolidate. It may be possible to prevent the material 15 from leaking from the rear end side of the ground reinforcing core material 14. The injection amount of the solidifying material 15 supplied from the injection machine 19 in the injection work is formed between the hollow portion volume of the ground reinforcing core material 14 and the drilling hole 13 and the ground reinforcing core material 14. It can be set based on the volume of the fixing region 16a, the volume of the ground improvement region 16b for solidifying and improving the ground, and the like. Further, a mixer 18 is provided on the tip side of the first inner tube 171 and the second inner tube 172 in the present embodiment, and the binder 15 can be sufficiently mixed and stirred in the stirring blade portion 182 of the mixer 18. it can. By mixing and stirring the binder 15 at the position immediately before the injection into the ground in this way, it is suitably suppressed that the solidified material 15 blocks the hollow portion 140 of the core material 14 for reinforcing the ground. it can.

When the injection work of the binder 15 is completed, the rear end spraying process is performed in step S104. In the rear end spraying process, sprayed concrete is sprayed onto the core material casting peripheral region R in the side wall portion 6 of the tunnel T. 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 sprayed concrete on the core material casting peripheral region R. After that, sprayed concrete is applied to the core material casting peripheral area R so that the mounting adapter 173 of the ground reinforcing core material 14 exposed in the core material casting peripheral area R in the side wall portion 6 of the tunnel T is buried. Spray to the specified thickness. Then, when the rear end spraying process is completed, as shown in FIGS. 2 and 3, a pair of left and right ground reinforcing portions 12 are constructed with respect to the new section of the tunnel T. In this way, after newly constructing a pair of left and right ground reinforcement portions 12 in the new section, ground excavation in the next excavation cycle section is performed. In the present embodiment, by alternately repeating the construction of the support structure and the ground reinforcement structure 10 for the new section for each excavation cycle section, the subsidence of the lateral ground 1a is suppressed and the ground in front of the face 1b is covered. It can be reinforced before excavation.

As described above, in the ground reinforcement method in the present embodiment, when the ground reinforcement core material 14 is placed from the side wall portion 6 of the tunnel T to the side ground 1a, the ground drilling direction Db and the tunnel The ground drilling angle θ1 formed by the excavation direction DT is set to an acute angle, and the ground reinforcement portion 12 constructed in the new section is set from the side wall portion 6 of the tunnel T to the ground in front of the face 2 located in front of the face 2. The arrangement was made to extend diagonally forward. According to this, at least a part of the ground reinforcing portion 12 (in the present embodiment, most of it as shown in FIG. 3) can be extended to the ground in front of the face 1b. As a result, before excavating the face front ground 1b in the next excavation cycle section, the rigidity of the ground reinforcement core material 14 of the ground reinforcement portion 12 and the strength of the consolidation reinforcement portion 16 determine the face front ground. 1b can be reinforced in advance. As a result, the binding force of the face front ground 1b in the tunnel T is enhanced, and it is possible to suitably suppress the tunnel T from sinking when excavating the face front ground 1b.

Further, according to the ground reinforcement method in the present embodiment, since a set of ground reinforcement portions 12 are formed on the left and right side grounds 1a of the tunnel T for each excavation cycle section, the left and right sides of the tunnel T are formed. The tunnel 1a can be suitably reinforced.

Further, in the ground reinforcement method in the present embodiment, since the ground reinforcement portion 12 is formed in the horizontal direction from the side wall portion 6 of the tunnel T into the lateral ground 1a, subsidence of the tunnel is preferable. Can be suppressed. Further, in the present embodiment, as shown in FIG. 3, since the ground reinforcing portion 12 is formed so as to cross the slip line of the lateral ground 1a, the lateral ground 1a is loosened. This can be suitably suppressed. Further, in the ground reinforcement method according to the present embodiment, the height of the ground reinforcement portion 12 formed in the ground 1 is made to correspond to the vicinity of the legs of the steel support work 4. By constructing the ground reinforcing portion 12 at a height near the legs of the steel support 4 where the load of the ground 1 is concentrated in this way, the sinking of the tunnel can be suppressed more preferably. However, in the ground reinforcement method of the present embodiment, it is sufficient to form the ground reinforcement portion 12 in the ground 1 from the side wall portion 6 of the tunnel T, and the ground reinforcement portion 12 constructed in the ground 1 is not necessarily the ground reinforcement portion 12. It is not necessary to correspond to the vicinity of the legs of the steel support work 4.

Further, in the ground reinforcement method in the present embodiment, the ground reinforcement portion 12 is formed for each excavation cycle section in which the ground 1b in front of the face is excavated for a certain section in the tunnel excavation direction DT. According to this, it is possible to continuously provide each reinforcing portion forming pitch RP along the tunnel excavation direction DT in the lateral ground 1a of the tunnel T. According to this, the ground reinforcement structure 11 which is an aggregate of the ground reinforcement portions 12 which are continuously provided in the tunnel excavation direction DT becomes strong, and a larger ground load is supported by the ground reinforcement structure 11. It is possible to more preferably suppress the sinking of the tunnel T.

In particular, in the present embodiment, since the ground drilling angle θ1 formed by the ground drilling direction Db and the tunnel drilling direction DT is set to a sharp angle, the ground drilling direction Db is in the direction orthogonal to the tunnel drilling direction DT. Compared to the case of setting to (that is, when the core material 14 for ground reinforcement is placed in the direction orthogonal to the tunnel excavation direction DT), the central axis of the adjacent ground reinforcement portion 12 in the lateral ground 1a. The distance between the two (hereinafter referred to as "reinforcing portion central axis pitch") W1 can be reduced.

Here, FIG. 14 is a diagram for explaining the central axis pitch W1 of the reinforcing portion of the ground reinforcing portion 12 according to the first embodiment. Reference numeral CL2 in FIG. 14 is the central axis of the ground reinforcing portion 12. Here, the central axis CL2 of the ground reinforcing portion 12 can also be said to be the central axis of the ground reinforcing core member 14. Further, the central axis CL2 of the ground reinforcing portion 12 is parallel to the ground drilling direction Db. Further, the reinforcing portion central axis pitch W1 refers to the distance between the central axes CL2 of the ground reinforcing portion 12 in the direction orthogonal to the central axis CL2 of the ground reinforcing portion 12. Further, FIG. 14 also illustrates an example in which the ground drilling angle θ1 formed by the ground drilling direction Db and the tunnel excavation direction DT is set to 45 °. Further, in FIG. 14, the drilling hole 13 is not shown.

In the present embodiment, since the ground drilling angle θ1 is an acute angle, the reinforcing portion central axis pitch W1 is smaller than the reinforcing portion forming pitch RP as shown in FIG. In the example shown in FIG. 14, since the ground drilling angle θ1 is 45 °, the reinforcing portion central axis pitch W1 is 1 / √2 times (about 0.7 times) the reinforcing portion forming pitch RP. On the other hand, when the ground drilling angle θ1 is set to a right angle (when the ground reinforcement core material 14 is placed in the direction orthogonal to the tunnel excavation direction DT), the central axis CL2 of the ground reinforcement portion 12 Is orthogonal to the tunnel excavation direction DT, so that the reinforcing portion central axis pitch W1 of the ground reinforcing portion 12 is equal to the reinforcing portion forming pitch RP.

Therefore, as in the present embodiment, by making the ground drilling angle θ1 an acute angle, the reinforcing portion central axis pitch W1 (center axis spacing of the ground reinforcing core member 14) of the ground reinforcing portion 12 is changed to the reinforcing portion. It can be narrower than the formation pitch RP. As a result, if the injection amount of the binder 15 in the above-mentioned injection work is the same, the separation dimension W2 between the adjacent ground reinforcing portions 12 in the ground 1 also makes the ground drilling angle θ1 perpendicular. It can be made smaller than the case where it is set (when the core material 14 for reinforcing the ground is placed in the direction orthogonal to the tunnel excavation direction DT). That is, the width of the unreinforced region of the ground located between the ground reinforcing portions 12 can be narrowed. As a result, the planar ground reinforcing structure 11 can be constructed in the ground 1 by the densely arranged ground reinforcing portions 12, and the reinforcing effect of the ground 1 becomes very excellent. Therefore, according to the ground reinforcement structure 11 in the present embodiment, a larger ground load can be supported, and the subsidence of the tunnel T can be suitably suppressed.

In the ground reinforcement method according to the first embodiment, the ground reinforcement portion 16 (ground improvement region 16b) of the ground reinforcement portions 12 adjacent to each other in the ground reinforcement structure 11 is connected to each other. 12 may be formed. By doing so, it is possible to construct a planar ground reinforcement structure 11 in which the mountain reinforcement portions 12 included in the ground reinforcement structure 11 are integrated, and the ground reinforcement effect. Will be extremely good. In order to make the ground improvement regions 16b in the ground reinforcing portions 12 adjacent to each other continuous as described above, the ground drilling angle θ1, the reinforcing portion forming pitch RP, and the injection amount of the binder 15 in the injection work It can be realized by adjusting the above.

Further, in the ground reinforcement method in the present embodiment, the ground reinforcement portions 12 in each excavation cycle section are formed at the same positions in the cross-sectional view of the tunnel T. According to this, the ground reinforcement portion 12 in each excavation cycle section can be arranged more densely. As a result, the reinforcing effect of the ground 1 can be further enhanced. In the present embodiment, the ground reinforcement portion 12 in each excavation cycle section is extended and arranged in the horizontal direction, but the present invention is not limited to this. For example, the mountain reinforcement portions 12 may be constructed at various locations so that the elevation angles or depression angles of the ground reinforcement portions 12 in each excavation cycle section are equal to each other.

Further, according to the ground reinforcement method in the present embodiment, each of the ground reinforcement portions 12 in each excavation cycle section has the same ground drilling angle θ1. According to this, when the ground reinforcement core material 14 is driven into the lateral ground 1a in the new section, the ground reinforcement core material 14 interferes with the existing ground reinforcement portion 12 or is already installed. It is possible to prevent damage to the ground reinforcing portion 12.

In the present embodiment, the ground drilling angle θ1 when the ground reinforcing core material 14 is placed in the lateral ground 1a may be an acute angle, and is not limited to a specific angle, but is 30 ° to ~. It is preferably set in the range of 60 °. Here, when the total lengths of the ground reinforcing cores 14 are the same, the smaller the ground drilling angle θ1, the longer the ground reinforcing core 14 is driven in the tunnel digging direction DT. While a large L2 can be secured, the transverse driving length L3, which is the driving length in the tunnel transverse direction of the ground reinforcing core material 14, becomes smaller. On the contrary, the larger the ground drilling angle θ1, the smaller the drilling direction driving length L2, which is the driving length of the ground reinforcing core material 14 in the tunnel drilling direction DT, while the ground reinforcing core material It is possible to secure a large crossing direction driving length L3, which is the driving length in the tunnel crossing direction in 14. The larger the excavation direction driving length L2, the wider the range in which the face front ground 1b can be reinforced when the ground reinforcement portion 12 is constructed in the new section. Therefore, the ground reinforcement portion 12 is set with a crossing direction casting length L3 so that the slip line of the lateral ground 1a can be crossed, and the ground drilling angle θ1 is made as small as possible within such a range. It may be set to an angle. As a result, it is possible to secure the maximum amount of reinforcement and the reinforcement range of the front ground 1b of the face while suppressing the subsidence of the lateral ground 1a. In the present embodiment, the ground drilling angle θ1 of the mountain reinforcement portion 12 of the ground reinforcement structure 11L and the extension angle θ1 of the reinforcement portion of the mountain reinforcement portion 12 of the ground reinforcement structure 11R are set to different angles. You may set it.

Further, as the base material of the core material 14 for reinforcing the ground in the present embodiment, it is preferable that the yield strength is 400 kN / piece or more, the breaking strength is 600 kN / piece or more, and the shear strength is 200 kN / piece or more. By using such a core material 14 for reinforcing the ground with high rigidity and high strength, the rigidity and strength equal to or higher than those of steel pipes generally used as side piles are secured, and the ground is compared with the case of using steel pipes. The time required for placing on the mountain can be significantly reduced. As a result, the workability can be improved and the construction cost can be reduced. Further, according to the core material 14 for reinforcing the ground in the present embodiment, it is possible to shorten the driving time to the ground, so that it is possible to reduce the influence of drilling water and vibration on the ground. For example, KAT-R51 (manufactured by Catex) formed of carbon steel material S45C for mechanical structure can be suitably used as the core material 14 for reinforcing the ground. The KAT-R51 has an outer diameter of about 50 mm, a wall thickness of about 8 mm, and a weight of about 8.5 kg / m, which is much lighter than a steel pipe generally used as a side pile, and reduces construction time. Workability can be improved.

The type of the binder 15 is not particularly limited, and for example, a cement-based binder and a urethane-based binder may be appropriately selected depending on the state of the ground and the state of the spring water. In addition, it is preferable to use a urethane-based binder having excellent performance such as higher strength than the cement-based binder, rapid curing and rapid development of strength from curing, and easy penetration into the voids of the ground. is there.

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

Further, the ground reinforcing core material 14 applied to the present invention is not limited to the injection type hollow lock bolt. For example, a solid lock bolt may be used as the core material for reinforcing the ground. In this case, a hole is formed in the lateral ground 1a from the side wall portion 6 in the new section located near the face 2 of the tunnel T, and the hole is filled with a solidifying material as a fixing material and then inside the hole. A ground reinforcement portion may be formed in the ground by inserting a solid lock bolt into the ground. Hereinafter, the second embodiment will be described.

<Embodiment 2>
16 and 17 are schematic structural views of the ground reinforcement structure 10A constructed by the ground reinforcement method according to the second embodiment. FIG. 16 shows a schematic structure of the ground reinforcement structure 10A in the cross-sectional direction of the tunnel T, and FIG. 17 shows a planar structure of the ground reinforcement structure 10A. The members, structures, terms, etc. that are common to the first embodiment will be described in detail by using the same reference numerals.

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

FIG. 18 is a schematic view illustrating the ground reinforcement portion 12A according to the second embodiment. The ground reinforcing portion 12A includes a drilling 13 formed in the lateral ground 1a, a ground reinforcing core 14A inserted into the drilling 13, and a consolidation material 15 filled in the drilling 13. Includes a consolidation reinforcement 16A formed by curing. Similar to the ground reinforcement portion 12 of the first embodiment, the ground reinforcement portion 12A constructs a support structure in the new section of the tunnel T, and then performs the preparatory work described in FIG. 9 to perform the preparatory work described in FIG. A hole is drilled from the target placement position PT in the above to the lateral ground 1a. The drilling to the lateral ground 1a can be performed by using a hydraulic drifter or the like, and the drilling 13 is formed along the ground 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 an acute angle. Therefore, at least a part of the drilling 13 extending diagonally forward from the side wall portion 6 of the tunnel T toward the face front ground 1b reaches the face front ground 1b and extends into the face front ground 1b. Will be there.

Next, after filling the hole 13 with a predetermined amount of the binder (fixing material) 15, the ground reinforcing core material 14A is inserted into the hole 13. In the present embodiment, the core material 14A for reinforcing the ground uses a solid type all-screw lock bolt, but the lock bolt used is not particularly limited. Further, the ground reinforcing core material 14A may be formed by connecting a plurality of bolts. The solidifying material (fixing material) 15 is not particularly limited, but may be a cement-based solidifying material (fixing material). After curing the binder 15, a washer 147, a bell washer (not shown), etc. are installed on the rear end side of the core material 14A for reinforcement of the ground, and the nut 148 is fixed with a torque wrench or the like to reinforce the ground. The construction of part 12A is completed. The consolidation reinforcing portion 16A is formed by hardening the solidifying material 15 filled in the drilled hole 13, and the solidifying reinforcing portion 16A forms the surrounding ground and ground of the drilling 13 (ground reinforcement core material 14A). The mountain reinforcing core material 14A is fixed.

As a result, as shown in FIG. 17, a ground reinforcing portion 12A formed in the ground so as to extend at least a part of the ground in front of the face can be newly installed in the new section of the tunnel T. As a result, before excavating the face front ground 1b in the next excavation cycle section, the face front ground is determined by the rigidity of the ground reinforcement core material 14A of the ground reinforcement portion 12A and the strength of the consolidation reinforcement portion 16A. 1b can be reinforced in advance. As a result, the binding force of the face front ground 1b in the tunnel T is enhanced, and it is possible to suitably suppress the tunnel T from sinking when excavating the face front ground 1b.

Although the embodiments and modifications of the ground reinforcement method according to the present invention have been described above, the present invention is not limited to the above embodiments and modifications, and can be appropriately modified without departing from the spirit of the present invention. .. For example, in the above-described embodiment and modified example, an example applied to the construction of the upper half of the tunnel has been described, but the ground reinforcement method according to the present invention may be applied to the construction of the lower half of the tunnel.

T ... Tunnel 1 ... Ground 2 ... Face 3 ... Primary sprayed concrete layer 4 ... Steel support 5 ... Secondary sprayed concrete layer 6 ... Side wall 10 ... Ground reinforcement structure 11 ... Ground reinforcement structure 12 ... Ground reinforcement 13 ... Drilling 14 ... Ground reinforcement core 15 ... Baking material 16 ...・ Solid reinforcement

Claims (9)

A hole is drilled in the ground on the side from the side wall of the tunnel located near the face of the tunnel, and a consolidation material is injected into the hole with the core material for reinforcing the ground inserted in the hole. This is a ground reinforcement method for forming a ground reinforcement portion in the ground by inserting a core material for ground reinforcement into the hole after filling the hole with a solidifying material.
The ground reinforcement portion is formed so that the ground drilling angle formed by the drilling direction and the tunnel excavation direction with respect to the lateral ground is set to an acute angle, and at least a part thereof extends to the ground in front of the face. Be done,
Ground reinforcement method. The ground reinforcement portion is formed at a height corresponding to the vicinity of the leg portion of the steel support work included in the support structure of the tunnel.
The ground reinforcement method according to claim 1. The ground reinforcement portion is formed for each excavation cycle section for excavating a certain section of the ground in front of the face in the tunnel excavation direction.
The ground reinforcement method according to claim 1 or 2. A set of the above-mentioned ground reinforcements is formed on the left and right grounds of the tunnel for each excavation cycle section.
The ground reinforcement method according to claim 3. The ground reinforcements in each excavation cycle section are formed at the same position in the cross-sectional view of the tunnel.
The ground reinforcement method according to claim 3 or 4. Each of the ground reinforcements in each excavation cycle section has the same ground drilling angle.
The ground reinforcement method according to any one of claims 3 to 5. The ground reinforcement portion includes a ground improvement region formed by hardening the binder injected into the ground around the drilling hole.
The ground reinforcement method according to any one of claims 1 to 6. A plurality of ground reinforcement portions are continuously provided in the ground so that the ground improvement areas in the ground reinforcement portion are connected.
The ground reinforcement method according to claim 7. The ground reinforcement portion 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 portion in each excavation cycle section is formed so that the ground improvement areas of the ground reinforcement portions adjacent to each other are connected to each other.
The ground reinforcement method according to claim 8.

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