JP2021095719A - Natural ground reinforcement method - Google Patents

Abstract

To provide a natural ground reinforcement method improving reinforcement effect of forward natural ground with a simple method.SOLUTION: Long drilled holes 10 longer than length of core material 1 are drilled in forward natural ground 3, where the core members 1 are pressed and inserted in the drilled holes 10, respectively, for a natural ground reinforcement method to reinforce the natural ground by injecting natural ground improvement material 8 inside of core members 1 after a plurality of hollow core members 1 are installed radially in forward natural ground 3 of a tunnel outer periphery. Preferably, the drilled hole 10 is drilled in a direction for a tunnel cross section inner than timbering 4b installed adjacent to the forward natural ground 3 to the natural ground 3. Preferably, length of the drilled hole 10 is equal to or longer by one excavating length of the tunnel than that of the core member 1. Preferably, a pressing tool to press the core member 1 into the drilled hole 10 is provided, which is recovered after pressing the core member 1.SELECTED DRAWING: Figure 3

Description

The present invention relates to a ground reinforcement method, and more particularly to a ground reinforcement method for improving the reinforcement effect of the front ground by a simple method.

In tunnel excavation in a ground with low consolidation such as earth and sand or a ground with high collapse such as a crush zone, a hollow core material is placed in the front ground around the tunnel prior to excavation of the tunnel. The method of injecting a ground improvement material into the ground through the core material of the tunnel to reinforce the ground is widely adopted, and it is called a pre-construction work. This pre-construction is generally performed by the procedure shown in FIGS. 7 to 8, for example.
Here, FIG. 7A shows a vertical cross section of the tunnel excavation portion, which is a mountain side surface position 31, a tunnel side surface position 21, and a face 2 in the tunnel excavation with respect to the front ground 3. , Support work 4 is built and formed.
The interval (1 excavation length) W of each support 4 is usually about 1 m. Further, the support work 4 is covered with sprayed concrete 5. Although not shown, usually, lining concrete and mirror sprayed concrete are sequentially laid on the sprayed concrete 5.
As shown in FIG. 7A, a drilling 10 is formed from between the support 4b erected after excavation of the tunnel and the support 4a erected one unit in front of the support 4b toward the front ground 3.
Next, a hollow core material 1 is inserted into the hole 10 and a caulking agent 9 is filled in the gap between the hole 10 at the rear end 1b of the core material 1 and the core material 1, and the caulking agent 9 is filled in the ground through the core material 1. Prevent the leakage of the ground improvement material to be injected.
The length of the core material 1 is 3 to 4 m, and the length of the drilling hole 10 formed in the front ground 3 on the outer circumference of the tunnel is substantially the same as the length of the core material 1.
After that, as shown in FIG. 7B, an injection adapter is installed at the rear end portion 1b of the core material 1, and the ground improving material 8 such as cement or urethane is injected into the core material 1.
The ground improvement material 8 injected into the core material 1 is discharged into the ground around the core material from a discharge hole provided on the outer peripheral portion of the core material 1 and fills voids and cracks in the ground.

As described above, in the prior art, the drilling 10 is formed from between the support 4b which is erected after the tunnel excavation and the support 4a which is erected one unit in front of the support 4b toward the front ground 3. So to speak, the drilling 10 is formed from the position returned from the excavation position.
Therefore, for example, as shown in FIG. 8A, when the length L of the core material is 3 m and the excavation length W of one tunnel is 1 m, the core left in the front ground 3 from the excavated part after the construction. The horizontal length D (preceding length) of the material 1 is 1.2 m or less. In this way, the pre-received length D is less than half of the length L of the core material, and the front ground 3 of the core material 1 is loose in a highly collapsible ground, so that the ground collapses. ..
Further, in the prior art, a drilling hole 10 is formed from between the support 4b erected after the tunnel excavation and the support 4a erected one unit in front of the tunnel 4a toward the front ground 3, but in this case, the rock drilling machine. It is necessary to increase the angle of the drilling 10 in order to prevent the guide cell and the drifter of the above from interfering with the support work 4b in front of one unit.
Then, as shown in FIG. 8A, in the prior art, the elevation angle θ of the core material 1 from the mouth portion of the drilling 10 is approximately 25 °, and the core material 1 and the support work 4b, 4c are used during excavation after construction. A peeling point 35 from the ground in between occurs.
As shown in FIG. 8B, after one excavation is carried out, a support 4c is installed, a hole 11 for the next excavation is formed, and the excavation method according to the above construction procedure is repeated. I will proceed.

Here, a core material formed by connecting a plurality of pipe materials has been proposed (see, for example, Patent Document 1). The core material described in Patent Document 1 has a configuration in which a plurality of pipe materials are sequentially connected and driven into the front ground, and after the terminal tube of the driven core materials is pulled out and removed, the ground is passed through the remaining pipe material. This is a method of injecting an improving agent. According to this construction method, the rock drill does not interfere with the terminal pipe during excavation.

Japanese Unexamined Patent Publication No. 2016-069908

However, in the case of the construction method described in Patent Document 1, it is necessary to prepare a plurality of pipe materials and connect them in order to form the core material. Further, after driving the formed core material into the front ground, it is necessary to remove only the terminal tube.
The present invention has been made in view of such problems, and an object of the present invention is to provide a ground reinforcement method for improving the reinforcement effect of the front ground by a simple method.

In order to solve the above problems, in the invention of the ground reinforcement method according to claim 1, a plurality of hollow core materials are radially placed in the front ground on the outer periphery of the tunnel prior to excavation of the tunnel. In the ground reinforcement method that reinforces the ground by injecting the ground improvement material into the core material,
The gist is to form a hole longer than the length of the core material in the front ground and push the core material into the hole.
According to the invention of the ground reinforcement method according to claim 2, in the description of claim 1, the drilling is directed from the inside of the tunnel cross section inside the support work laid in the immediate vicinity of the front ground toward the front ground. The gist is that it is formed.
The invention of the ground reinforcement method according to claim 3 is based on the gist of claim 1 or 2, that the length of the drilling is longer than the length of the core material by one excavation length or more of the tunnel.
The invention of the ground reinforcement method according to claim 4 is provided in any one of claims 1 to 3, wherein the core material is provided with a pushing jig for pushing the core material into the drilling hole. The gist is to collect after pushing.

According to the ground reinforcement method of the present invention, a hole longer than the length of the core material is formed in the front ground, and the core material is pushed into the hole. The length of the material can be made longer, and the reinforcing effect of the front ground can be enhanced.
In addition, when drilling is formed from the inside of the tunnel cross section inside the support work laid in the immediate vicinity of the front ground toward the front ground, the ground between the core material and the support work during excavation after construction. It is possible to reduce the peeling from the mountain.
Further, when the length of the hole is longer than the length of the core material by one excavation length or more of the tunnel, the length of the core material left in the front ground from the excavated part after the construction can be made longer. The reinforcement effect of the front ground can be improved more appropriately.
If a push-in jig for pushing the core material into the hole is provided and the core material is collected after being pushed in, it will not interfere with tunnel excavation and the push-in jig can be used repeatedly. Efficiency can be increased.

The present invention will be further described in the following detailed description with reference to the plurality of references mentioned with reference to non-limiting examples of typical embodiments according to the invention. Similar members are shown through several figures.
It is explanatory drawing which concerns on the ground reinforcement method of an Example, (a) shows the formation of a hole, and (b) shows the insertion of a core material. It is explanatory drawing which concerns on the ground reinforcement method of an Example, (a) is the installation of the pushing jig for pushing a core material into a hole, and (b) is the state which pushed the pushing jig. It is explanatory drawing which concerns on the ground reinforcement method of an Example, (a) shows the state which pushed-in jig was collected, and (b) is the state which injected and filled the ground improvement material into the core material. It is explanatory drawing which concerns on the ground reinforcement method of an Example, (a) shows excavation, (b) shows the formation of the next drilling. In relation to the ground reinforcement method of the embodiment, (a) is the formation of a hole, (b) is the insertion of the core material, (c) is the installation of the pushing jig, and (d) is the pushing jig. Push-in, (e) is an explanatory view showing recovery of the push-in jig. In relation to the ground reinforcement method of the embodiment, (a) is the insertion of an injection pipe into the core material, (b) is caulking for closing the rear end of the core material, and (c) is the ground improvement material. Injection, (d) is an explanatory diagram showing the formation of a diffusion region of the ground improving agent. It is explanatory drawing which concerns on the ground reinforcement method of the conventional example, (a) shows formation of a hole and insertion of a core material, and (b) shows injection of a ground improvement material. It is explanatory drawing which concerns on the ground reinforcement construction method of the conventional example, (a) shows excavation, and (b) shows the formation of the next drilling.

The matters shown here are for exemplifying and exemplifying embodiments of the present invention, and are considered to be the most effective and effortless explanations for understanding the principles and conceptual features of the present invention. It is stated for the purpose of providing what seems to be. In this regard, it is not intended to show structural details of the invention beyond a certain degree necessary for a fundamental understanding of the invention, and some embodiments of the invention are provided by description in conjunction with the drawings. It is intended to clarify to those skilled in the art how it is actually realized.

In the ground reinforcement method in the present embodiment, as shown in FIGS. 1 to 4, a plurality of hollow core materials 1 are radially placed in the front ground 3 on the outer periphery of the tunnel prior to excavation of the tunnel, and the core material 1 is formed. In the ground reinforcement method of injecting a ground improvement material into the inside of a tunnel to reinforce the ground, a hole 10 longer than the length of the core material 1 is formed in the front ground 3 and the core material 1 is placed in the hole 10. It is characterized by pushing.
FIGS. 1 to 4 show a vertical cross section of the tunnel excavation portion according to the embodiment. Here, the "cross section" is intended to be a cross section substantially orthogonal to the axial direction of the tunnel.

In FIG. 1A, the front ground 3 has a mountain-side surface position 31, a tunnel-side surface position 21, and a face 2 in excavation of a tunnel, and a support 4 is built-in and formed.
Further, the support work 4 is covered with sprayed concrete 5. Although not shown, usually, lining concrete and mirror sprayed concrete are sequentially laid on the sprayed concrete 5.

Hereinafter, the construction procedure of this embodiment will be described.
As shown in FIG. 1 (a), from the inside of the tunnel cross section 40 inside the support 4b laid in the immediate vicinity of the excavation site toward the front ground 3, the drill jumbo (drilling heavy machine) is directed toward the front ground 3. To form a hole 10.
Next, the rod and bit for drilling are collected, and the core material 1 is inserted into the drilling hole 10 as shown in FIG. 1 (b).

As shown in FIG. 1A, the drilling hole 10 is formed from the face 2 below the surface position 21 on the tunnel side toward the front ground 3.
The drilling hole 10 is preferably formed at an elevation angle of 10 to 20 degrees from the mouth portion 10b, more preferably 12 to 18 degrees, and particularly preferably 14 to 16 degrees. If it is less than 10 degrees, the drill jumbo may interfere with the support 4b when the hole 10 is formed.
On the other hand, if the temperature exceeds 20 degrees, the length of the core material 1 pushed into the hole 10 in the horizontal direction becomes short, and there is a possibility that a sufficient reinforcing effect of the front ground 3 cannot be obtained.

The length of the drilling 10 is not particularly limited as long as it is longer than the length 1 of the core material, but it is preferably one drilling length W or more. Here, one excavation length W is the distance between the support 4a and the support 4b in the excavation direction. Further, as shown in FIG. 4A, which will be described later, it is preferable that the rock drill does not interfere with the core material 1 during excavation. Therefore, it is preferable that the core material 1 is left above the surface position 31 on the mountain side of the tunnel.
In this embodiment, one excavation length W is 1 m, the length of the drilling hole 10 is set to 4 m, and the length of the core material 1 is set to 3 m.

As shown in FIG. 5B, the core material 1 is formed in a tubular shape in which the front end portion 1a is closed and the rear end portion 1b is open. Then, a discharge hole 1h for discharging the ground improving agent described later is provided.
The material of the core material 1 is not particularly limited as long as it is a hollow tube material, and may be made of steel, carbon fiber reinforced resin, glass fiber reinforced resin, or other various fiber reinforced resins.

After inserting the core material 1 into the drilling hole 10, the core material 1 is further pushed into the drilling hole 10. In order to increase the horizontal length of the core material 1 in the ground, it is preferable to push it as far as possible. It is particularly preferable that the tip of the core material 1 reaches the innermost part 10a.
The method of pushing the core material 1 into the drilling hole 10 is not particularly limited, and various methods can be adopted. For example, a method using a pushing jig can also be adopted.
For example, as shown in FIGS. 2 (a) and 5 (c), a pushing jig 6 is attached to the rear end portion 1b of the core material 1, and the pushing jig 6 is pushed in to obtain FIG. 2 (b). And as shown in FIG. 5D, the core material 1 can be inserted into the drilling hole 10. The shape and mounting method of the pushing jig 6 are not particularly limited as long as the core material 1 can be pushed.
The tip portion 6a of the pushing jig 6 may be detachably attached to the rear end portion 1b of the core material 1 by screwing, or may be covered with the core material 1. Further, the pushing jig 6 may be made of only a columnar rod-shaped member.

The length of the pushing jig 6 is not particularly limited as long as the core material 1 can be pushed to the innermost part of the drilling hole 10, but in this embodiment, it is set to 1 m and as shown in FIG. 5 (d). When the core material 1 is pushed to the innermost part 10a of the drilling hole 10, the rear end portion 6b of the pushing jig 6 is substantially flush with the mouth portion 10b of the drilling hole 10.
The material of the pushing jig 6 is not particularly limited, and a suitable one can be selected from wooden, resin, steel and the like.
In order to push the core material 1 to the innermost part 10a of the drilling hole 10 by the pushing jig 6, it is possible to use human power or the hydraulic pressure of the rock drill.

After pushing the core material 1 to the innermost part 10a of the drilling hole 10, the pushing jig 8 is pulled out from the drilling hole 10 and collected. Then, as shown in FIGS. 3 (a) and 5 (e), the hole portion 10c of only the drilling hole 10 remains at the place where the pushing jig 8 is pushed.
The method for pulling out the pushing jig 8 is not particularly limited, and the pushing jig 8 may be pulled out manually as it is. A through hole or the like is provided in the vicinity of the rear end portion 6b of the pushing jig 6, and a hook metal fitting or the like is provided in the through hole. It may be stopped and pulled out manually or with a pulling machine.

Next, as shown in FIG. 3B, the ground improving agent 8 is injected into the core material 1. The type of the ground improving agent 8 is not particularly limited, and urethane-based, cement-based, water glass-based, or other injection materials can be preferably used.
Specifically, as shown in FIG. 6A, an injection jig 7 for injecting the ground improvement material 8 into the core material 1 is inserted from the rear end portion 10b of the drilling hole 10.
The length of the injection jig 7 varies depending on the type of the ground improvement material 8, but it is preferable that the injection port 7b is a length that protrudes from the mouth portion 10b of the drilling hole 10.
The material of the injection jig 7 is not particularly limited, but a lightweight material such as nylon or vinyl chloride is preferable.

As shown in FIG. 6B, after the injection jig is inserted into the core material 1, the rear end portion 1b of the core material 1 and the hole 10 are formed in order to prevent leakage of the ground improving agent 8. The gap between them is filled with the caulking agent 9.
The material of the caulking agent is not particularly limited, and a suitable one can be appropriately selected from urethane-based, silicone-based, modified silicone-based, polysulfide-based caulking agents, mortar, and the like.

After that, as shown in FIG. 6C, the ground improvement material 8 is injected from the injection port 7b of the injection jig 7. Then, the ground improving material 8 flows into the core material 1 from the tip 7a of the injection pipe 7. Then, the ground improving material 8 that has flowed into the core material 1 is discharged into the ground 3 around the core material 1 from the discharge holes 1h provided on the outer peripheral portion of the core material 1, and voids and cracks in the ground. Is filled in to form a diffusion zone 85.

After that, as shown in FIG. 4A, excavation proceeds from the face 2 in the direction of the arrow. At that time, since the core material 1 is not left on the upper part of the excavated portion in advancing one excavation length, the rock drill does not interfere with the core material 1.
Then, as shown in FIG. 4 (b), after one excavation is advanced, a support 4c is installed, a hole 11 for the next excavation is formed, and the excavation is repeated by repeating the construction method according to the above procedure. I will proceed.

[Effect of Examples]
As shown in FIG. 4A, when the length L of the core material is 3 m and the excavation length W of the tunnel is 1 m, the horizontal angle θ of the drilling 10 is 15 degrees, so that the front is forward. The horizontal length D (preceding length) of the core material 1 left on the ground 3 can be secured to be 2.8 m or more.
On the other hand, as shown in FIG. 8A, in the prior art, the elevation angle θ from the mouth portion 10b of the drilling 10 is required to be about 25 degrees, and the core material 1 is left behind from the mouth portion of the drilling 10. Similarly, when the length L of the core material is 3 m and the excavation length W is 1 m, the length D of the core material 1 left in the front ground from the excavated cross section is 1.2 m or less. ing.
As described above, in the present invention, even if a core material having the same length as that of the conventional technique is used, the horizontal length of the core material left on the front ground from the excavated part after construction is made longer than that of the conventional technique. Is possible, and the reinforcement effect of the front ground is improved.

The above examples are for illustration purposes only and are not to be construed as limiting the invention. Although the present invention has been described with reference to typical embodiments, the language used in the description and illustration of the invention is understood to be descriptive and exemplary rather than restrictive. As described in detail here, modifications can be made within the scope of the appended claims without departing from the scope or spirit of the invention in that form. Although specific structures, materials and examples have been referred to herein in detail of the invention, it is not intended to limit the invention to the disclosures herein, but rather the invention is claimed in the accompanying claims. It shall cover all functionally equivalent structures, methods and uses within the scope.

It is widely used as a technology related to the long steel pipe tip receiving method that reinforces the ground prior to excavating a tunnel.

1; core material, 2; face, 3; forward ground, 4 (4a, 4b, 4c); support work,
5; Shotcrete, 6; Pushing jig, 7; Injection pipe, 8, Ground improvement material,
10, 11; drilling, 40; tunnel cross section inside the support,
D; first receiving length, L; core material length, W; 1 excavation length.

Claims (4)

In the ground reinforcement method in which a plurality of hollow core materials are radially placed in the front ground on the outer circumference of the tunnel prior to excavation of the tunnel, and the ground improvement material is injected into the core material to reinforce the ground. ,
A ground reinforcement method characterized in that a hole longer than the length of the core material is formed in the front ground and the core material is pushed into the hole. The ground reinforcement method according to claim 1, wherein the drilling is formed from the inside of the tunnel cross section inside the support work laid in the immediate vicinity of the front ground toward the front ground. The ground reinforcement method according to claim 1 or 2, wherein the length of the hole is longer than the length of the core material by one excavation length or more of the tunnel. The ground reinforcement method according to any one of claims 1 to 3, further comprising a pushing jig for pushing the core material into the drilling hole, and collecting the core material after pushing it.

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