Ground reinforcement method

Abstract

To provide a ground reinforcement work capable of reliably fixing a reinforcing material in a borehole while allowing the use and extraction of a casing used in forming the borehole and left in the borehole. [Solution] A rod-shaped reinforcing material 2 and a protective body 6 that is arranged to surround the part of the reinforcing material 2 near the tip side and allows grout 4 to pass in and out of it, and has higher shape retention than the packer 3, are inserted inside the casing 5 left in the drilled hole 1 formed in the ground G, covered with the packer 3, and the casing 5 is then pulled out from the drilled hole 1 and grout 4 is injected into the packer 3.

Description

[Technical Field]

[0001] The present invention is a ground reinforcement method suitable for use in, for example, reinforcing embankments (ground) that are determined to require reinforcement after the construction of a building. method Regarding. [Background technology]

[0002] Generally, when attempting to reinforce the ground (slope or slope), the ground reinforcement work used is not the anchor method, which stabilizes the ground with tensile force to prevent landslides and rock collapses, but rather the rock bolt method, which increases stability through friction and tensile force with the ground.With this rock bolt method, rod-shaped reinforcing materials (rock bolts) are inserted into holes drilled in the ground, and then grout is injected into the holes.

[0003] A drawback of this typical rock bolting method is that if there are gaps such as cracks that connect to the drilled hole and the grout injected into the drilled hole continues to leak out of the gaps, there will not be enough grout surrounding the reinforcement material, resulting in insufficient adhesion between the reinforcement material and the ground.

[0004] To overcome this drawback, Patent Document 1 proposes a bagged rock bolt method in which rod-shaped reinforcing material (steel rods) and a packer (cover) that covers the reinforcing material are inserted into a drilled hole in the ground, and then grout (cement paste) is injected into the packer. With this method, the packer can prevent grout from leaking out of the drilled hole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-49238 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with the bagged rock bolting method, if the wall of the drilled hole collapses before the grout can be injected into the packer, and the packer is crushed by the soil that has entered the hole as a result of the collapse, the grout cannot be injected into the packer. This problem is thought to be particularly likely to occur in embankments.

[0007] One possible solution is to prevent the hole wall from collapsing by using the casing left in the borehole. However, even in this case, the hole wall may collapse between the time the grout is injected into the packer and the time the grout solidifies after the casing is removed, causing the packer to be crushed by the soil and sand, resulting in an insufficient amount of grout surrounding the reinforcement. Furthermore, waiting for the grout inside the packer to solidify before removing the casing increases the resistance to removal, making it difficult to complete. Even if the casing is successfully removed, a gap may form between the hole wall and the packer after removal, weakening the adhesive strength of the reinforcement. While these problems would not occur if the casing were left in the borehole, the lack of adhesion between the casing and the natural ground would result in the casing easily separating from the natural ground, and the relatively high cost of the casing would significantly reduce the economic viability of the project.

[0008] The present invention has been made with the above-mentioned matters in mind, and its object is to provide a ground reinforcement method that can ensure the adhesion of the reinforcement material to the ground while allowing the use and extraction of a casing that has been used to form a hole and left in the hole. method The purpose is to provide [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a ground reinforcement methodThe method involves inserting a rod-shaped reinforcement material inside the casing left in the drilled hole formed in the ground, a protective body with higher shape retention than the packer near the tip of the reinforcement material, and a packer that covers them and allows grout to pass in and out, and then pulling out the casing from the drilled hole and injecting grout into the packer. The protective body comprises a cylindrical wire mesh and a spiral core inserted inside the cylindrical wire mesh and applying a tension force to the cylindrical wire mesh in a direction in which the diameter of the cylindrical wire mesh expands. (Claim 1).

[0010] The above ground reinforcement method In this case, of the multiple reinforcing materials connected to form a length corresponding to the depth of the hole to be drilled, at least the portion near the tip of the reinforcing material inserted at the deepest part of the hole may be surrounded by a protective body (Claim 2). [Effects of the Invention]

[0011] The present invention provides a ground reinforcement method that allows the use and removal of a casing that is used to form a hole and left in the hole, while ensuring the secure attachment of the reinforcement material to the ground. method is obtained.

[0012] That is, the ground reinforcement of the inventions according to the claims of this application method Even if the hole wall collapses after the casing is pulled out, the protective body surrounding the part of the reinforcement near the tip will catch some of the soil and sand that enters the drilled hole, preventing the packer from being completely crushed, and will make it easier for the reinforcement to be surrounded by a sufficient amount of grout, thereby ensuring a reliable bond between the ground and the reinforcement.

[0013] Ground reinforcement according to the invention of claim 2 method In this case, a protective body is placed at the innermost position of the reinforcement material inserted furthest into the drilled hole, and it is possible to prevent the hole wall from collapsing at this position. This position is usually set deeper than the slip surface, and since it is the most important position to prevent the hole wall from collapsing when reinforcing the ground, this will be of great help in reinforcing the ground. method In this case, by omitting the installation of the protective body at positions other than those mentioned above, it is possible to simplify the installation of the protective body and thereby contribute to reducing construction costs. [Brief explanation of the drawings]

[0014] [Figure 1] 1(A) to 1(E) are explanatory views schematically showing steps of a ground reinforcing method according to one embodiment of the present invention. [Figure 2] 3A and 3B are a side view and a front view showing the configuration of a protection body used in the ground reinforcing method. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described below.

[0016] In this example, the ground reinforcement work is performed as shown in Figures 1(A) to 1(E). A rod-shaped reinforcing material 2 and a packer 3 covering the reinforcing material 2 are inserted into a borehole 1 (see Figure 1(A)) formed in the ground G, which constitutes a slope, for example. Then, grout 4 is injected into the packer 3 (see Figure 1(E)). The reinforcing material 2 and a protective body 6, which surrounds the tip of the reinforcing material 2 and allows grout 4 to pass through the reinforcing material 2 and has a higher shape retention than the packer 3, are inserted inside the casing 5 (see Figure 1(A)) that was used to form the borehole 1 and left in the borehole 1. The protective body 6 is then inserted inside the casing 5 (see Figure 1(A)). The protective body 6 is then inserted inside the casing 5, which is used to form the borehole 1 and left in the borehole 1. The protective body 6 is then inserted inside the casing 5, which is used to form the borehole 1 and has a higher shape retention than the packer 3. The protective body 6 is then inserted inside the casing 5 (see Figure 1(B)). The protective body 6 is then removed from the borehole 1 (see Figures 1(C) and 1(D)). Finally, grout 4 is injected into the packer 3 (see Figure 1(E)). This process is described in detail below.

[0017] The borehole 1 shown in Figure 1(A) is formed using, for example, a well-known drilling device (not shown) that uses a casing 5. After the borehole 1 is formed, the drill or other device of the drilling device is moved sideways (used when removing the casing), leaving only the casing 5 in the borehole 1.

[0018] Then, a reinforcing material 2 is inserted into the drilled hole 1 with the casing 5 left in place as shown in Fig. 1(A) as shown in Fig. 1(B). The reinforcing material 2 is, for example, a deformed steel bar.

[0019] When inserting the reinforcing material 2, an injection hose 7 for injecting grout is placed along the reinforcing material 2 and fixed to the reinforcing material 2 with a fixing means such as adhesive tape (not shown). At this time, the tip of the injection hose 7 is positioned close to the tip of the reinforcing material 2 (in the illustrated example, it is positioned slightly rearward of the tip of the reinforcing material 2).

[0020] Then, a protective body 6, which is cylindrical overall, surrounds the portion of the reinforcing material 2 near the tip and the tip of the injection hose 7, and these 2, 6, and 7 are covered with a packer (cloth packer) 3, and the reinforcing material 2 in this state is inserted into the drilled hole 1.

[0021] As shown in Figures 2(A) and 2(B), the protector 6 comprises a cylindrical wire mesh 9 and a spiral core 10 inserted inside the cylindrical wire mesh 9. The cylindrical wire mesh 9 is manufactured by intertwining wire rods (each wire rod constituting the diamond-shaped wire mesh extends in a roughly zigzag or spiral pattern, with adjacent wire rods intertwined where they approach each other) at both ends (both short sides) of a sheet-like diamond-shaped wire mesh to form a tube, and then appropriately bending both ends of each wire rod. The wire rods used for the cylindrical wire mesh 9 have a flattened cross-sectional shape (a shape obtained by squashing a circle or square), rather than a circular or square one, which reduces the wall thickness of the cylindrical wire mesh 9 and allows for an expansion of its internal space. The spiral core 10 is configured to apply a tension force to the cylindrical wire mesh 9 in the direction of expanding its diameter, thereby making the cylindrical wire mesh 9 less likely to undergo deformation that reduces its diameter.

[0022] In this example, the length L of the protective body 6 (see Figure 2(B)) is 1000 mm, the inner diameter d of the cylindrical wire mesh 9 is 50 mm, the mesh size of the cylindrical wire mesh 9 is 20 mm in length and width, the wire material constituting the cylindrical wire mesh 9 is a metal wire with a cross-sectional width of 3.5 mm and a thickness of 1.4 mm, and the wire material constituting the spiral core 10 is a metal wire with a diameter of 1.6 mm and a circular cross-section. Furthermore, if the drilling diameter is different, the shape of the protective body 6 shown above may be changed.

[0023] Here, if necessary, the protector 6 may be fixed to the reinforcing material 2 by an appropriate means.

[0024] After inserting the reinforcing material 2 into the drilled hole 1 together with the protector 6 and injection hose 7 as described above, another reinforcing material 2 is added to the rear end thereof, and this addition is repeated until a length corresponding to the depth of the drilled hole 1 is reached, and finally, a plurality of reinforcing materials 2 connected to form a predetermined length corresponding to the depth of the drilled hole 1 are inserted into the drilled hole 1. That is, in this example, of the plurality of reinforcing materials 2 connected to form a length corresponding to the depth of the drilled hole 1, the portion of the reinforcing material 2 inserted at the deepest part of the drilled hole 1 near its tip is surrounded by the protector 6. The length of each reinforcing material 2 is, for example, 5 m, and it is often the case that two to four of these are connected together (for a total length of about 10 to 20 m).

[0025] Meanwhile, the injection hose 7 has a length equal to or greater than the depth of the drilled hole 1, and each time a reinforcement 2 is added, the injection hose 7 can be placed along the reinforcement 2 being added and secured with a securing means such as adhesive tape (not shown). A confirmation pipe 8 for checking the grout is placed along the last reinforcement 2 to be added and secured with a securing means such as adhesive tape (not shown), with the tip of the confirmation pipe 8 located in an appropriate position (for example, near the entrance of the drilled hole 1). Furthermore, the packer 3 extends from the innermost part of the innermost reinforcement 2 to near the tip of the confirmation pipe 8 (a position slightly closer to the base from the tip of the confirmation pipe 8), and is installed so as to cover all reinforcements 2, protectors 6, and injection hoses 7 located in between.

[0026] Once the insertion of the reinforcement material 2 is completed, the casing 5 is removed from the drilled hole 1 (Figure 1(C)). Next, as shown in Figures 1(D) and 1(E), grout 4 is injected into the packer 3 through the injection hose 7. Once the flow of grout 4 through the check pipe 8 is confirmed, the check pipe 8 is closed and pressure is applied to the packer 3. Initially, the packer 3 injects grout 4, and the cement paste contained in the grout 4 passes through the mesh into the drilled hole 1. Gradually, the mesh becomes clogged with coarse particles, and eventually, as shown in Figure 1(E), the grout expands and presses against the inner wall of the drilled hole 1. The cement paste that passed through the mesh prior to this pressurization contributes to the adhesion of the packer 3 to the inner wall of the drilled hole 1, ensuring a secure bond of the reinforcement material 2 after the grout 4 hardens.

[0027] Incidentally, as shown in Figure 1 (C), after the casing 5 is pulled out, it is conceivable that the inner wall (hole wall) of the drilled hole 1 may collapse, allowing soil and sand to enter the drilled hole 1. However, in this example, even if the hole wall collapses after the casing 5 is pulled out, the protective body 6 provided to surround the portion of the reinforcing material 2 near the tip can receive some of the soil and sand entering the drilled hole 1, preventing the packer 3 from being completely crushed, and making it easier for the reinforcing material 2 to be surrounded by a sufficient amount of grout 4, thereby ensuring that the reinforcing material 2 is firmly fixed inside the drilled hole 1.

[0028] Furthermore, in the ground reinforcement work of this example, a protective body 6 is installed at the innermost position of the reinforcing material 2 that is inserted furthest into the drilled hole 1, thereby preventing the hole wall from collapsing at this position. This position is usually set deeper than the slip surface, and since this is the position where preventing the hole wall from collapsing is most necessary in reinforcing the ground, this greatly contributes to reinforcing the ground. Furthermore, in this ground reinforcement work, by omitting the installation of protective bodies 6 at positions other than those mentioned above, it is possible to simplify the installation of the protective bodies 6 and thereby contribute to reducing construction costs.

[0029] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the following modifications can be mentioned.

[0030] The above-mentioned ground reinforcement work is particularly suitable for use in reinforcing embankments (natural ground) that are determined to require reinforcement after the construction of a building, but it is not limited to this and may also be used, for example, to reinforce cut earth.

[0031] The protective body 6 is arranged to surround the reinforcing material 2, and any material that allows grout to pass in and out of it and has better shape retention than the packer 3 may be used. It is not limited to the above configuration, and may be, for example, a cylindrical plate-shaped member with a large number of through holes.

[0032] In the above embodiment, an injection hose 7 is used separately from the reinforcing material 2, but this is not limited to this. For example, a flow path for injecting grout 4 may be formed within the reinforcing material 2 to serve as the injection hose 7 (to serve as the injection hose 7 as well), in which case there is no need to use an injection hose 7 separately from the reinforcing material 2.

[0033] It goes without saying that the above modifications may be combined as appropriate. [Explanation of symbols]

[0034] 1 Drilling 2 Reinforcement 3. Packer 4. Grout 5 Casing 6 Protective Body 7 Injection hose 8 Check pipe 9 Cylindrical wire mesh 10 spiral core d Inner diameter of cylindrical wire mesh G Ground L Length of the protector m Mesh size of cylindrical wire mesh

Claims

1. Inside the casing left in the drilled hole formed in the ground, a rod-shaped reinforcing material is inserted, and a protective body with higher shape retention than the packer is placed near the tip of the reinforcing material, and a packer that covers them and allows grout to pass in and out is inserted, and the casing is then pulled out of the drilled hole and grout is injected into the packer. A ground reinforcement method characterized in that the protective body comprises a cylindrical wire mesh and a spiral core inserted inside the cylindrical wire mesh and applying a tensioning force in the direction of expanding the diameter of the cylindrical wire mesh.

2. A ground reinforcement method as described in claim 1, in which, of multiple reinforcing materials connected to form a length corresponding to the depth of the hole, at least the portion near the tip of the reinforcing material inserted at the deepest part of the hole is surrounded by a protective body.

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