Method and apparatus for installing ground anchor

Abstract

To provide a construction method and a construction device of a ground anchor capable of surely cutting the whole range in an outer casing.SOLUTION: This construction method of the ground anchor uses a rotary percussion type excavator having a cylindrical outer casing 12 for excavating the ground by rotating around an axis, and a shaft-like inner rod 14 arranged in the outer casing 12 and cutting the inside of the outer casing 12 by a cutting part 18 of the tip by rotating around the axis. A tip side 22 of the inner rod 14 is formed in a dogleg shape when viewed from a direction orthogonal to an axis C2 of a body 24 of the inner rod 14, and the whole range in the outer casing 12 is cut by the tip side 22 by rotating the body 24 around the axis C2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and device for installing a ground anchor. [Background technology]

[0002] Conventionally, ground anchors have been widely used to reinforce slopes, prevent deformation of earth retaining walls and revetments (mainly steel sheet piles), etc. There are three typical construction methods for these ground anchors: (A) packer type, (B) rotary percussion type (single pipe type), and (C) rotary percussion type (double pipe type).However, when the drilling length of the ground anchor is long (30 m or more) and the ground is mainly composed of gravel layers, the (C) rotary percussion type (double pipe type) is often used, as it has the highest efficiency in removing excavated soil (see, for example, Patent Document 1).

[0003] The standard construction procedure for the rotary percussion method (double-pipe method) is as shown in Figure 2. That is, (1) an outer casing 3 (e.g., a drill pipe with a diameter of approximately 165 to 210 mm) with a bit 2 attached to its tip and an inner rod 4 (see Figure 3) are rotated together using a drilling machine 1, and the tip bit 2 is used to excavate (cut) the gravel layer in the ground G until it reaches the specified depth, (2) the inner rod 4 is withdrawn, (3) tendon 5 is inserted, (4) the outer casing 3 is withdrawn with an extraction jack 6 while pressurized injection of grout material 7 is performed, (5) the tendon 5 is tensioned with a tensioning jack 8, and (6) the tendon is fixed to a pedestal 9. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-150773 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above construction procedure, during the excavation stage (1), the inner rod 4 has a smaller outer diameter than the outer casing 3, so its tip bends downward due to its own weight inside the outer casing 3. As shown in Figure 4, this may result in an area A above the tip of the outer casing 3 where gravel R cannot be excavated. This risk increases particularly as the drilling extension of the ground anchor increases, making it difficult to reach the design depth. Furthermore, if gravel with a diameter of approximately 30 to 50 mm is present in the ground to be excavated, the gravel R in the area A that cannot be excavated may not be excavated and may become stuck inside the outer casing, making it difficult to even rotate. For this reason, there was a need for technology that could eliminate the area A that cannot be excavated and reliably excavate the entire area inside the outer casing.

[0006] The present invention has been made in view of the above, and has an object to provide a ground anchor installation method and installation device that can reliably cut the entire area inside the outer casing. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the method of installing a ground anchor according to the present invention is a method of installing a ground anchor using a rotary percussion excavator having a cylindrical outer casing that rotates around its axis to excavate the ground, and an axial inner rod that is provided inside the outer casing and rotates around its axis to cut the inside of the outer casing with a cutting section at its tip, wherein the tip side of the inner rod is formed in a dogleg shape when viewed from a direction perpendicular to the axis of the main body of the inner rod, and by rotating the main body around its axis, the tip side cuts the entire area inside the outer casing.

[0008] Furthermore, the ground anchor installation device of the present invention is a ground anchor installation device that uses a rotary percussion excavator having a cylindrical outer casing that rotates around its axis to excavate the ground, and an axial inner rod that is provided inside the outer casing and rotates around its axis to cut the inside of the outer casing with a cutting section at its tip, wherein the tip side of the inner rod is formed in a dogleg shape when viewed from a direction perpendicular to the axis of the main body of the inner rod, and by rotating the main body around its axis, the entire area inside the outer casing can be cut at the tip side. [Effects of the Invention]

[0009] The ground anchor installation method of the present invention is a method of installing a ground anchor using a rotary percussion excavator having a cylindrical outer casing that rotates around its axis to excavate the ground, and an axial inner rod that is provided inside the outer casing and rotates around its axis to cut the inside of the outer casing with a cutting section at its tip, wherein the tip side of the inner rod is formed in a dogleg shape when viewed from a direction perpendicular to the axis of the main body of the inner rod, and by rotating the main body around its axis, the tip side cuts the entire area inside the outer casing, thereby achieving the effect of being able to reliably cut the entire area inside the outer casing.

[0010] Furthermore, the ground anchor installation device according to the present invention is a ground anchor installation device that uses a rotary percussion excavator having a cylindrical outer casing that rotates about its axis to excavate the ground, and an axial inner rod that is provided inside the outer casing and rotates about its axis to cut the inside of the outer casing with a cutting section at its tip, wherein the tip side of the inner rod is formed in a dogleg shape when viewed from a direction perpendicular to the axis of the main body of the inner rod, and by rotating the main body about its axis, the entire area inside the outer casing can be cut at the tip side, thereby achieving the effect of being able to reliably cut the entire area inside the outer casing. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an embodiment of a ground anchor installation method and installation device according to the present invention. [Figure 2] FIG. 2 is a diagram showing an example of a conventional method for installing a ground anchor. [Figure 3] FIG. 3 is a schematic diagram of the main parts of a conventional construction device, where (1) is the tip of the outer casing and (2) is the tip of the inner rod. [Figure 4] FIG. 4 is an explanatory diagram of the problems with the conventional method of installing ground anchors. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, preferred embodiments of a ground anchor installation method and installation device according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these preferred embodiments.

[0013] As shown in FIG. 1, a ground anchor installation device 10 according to an embodiment of the present invention is a device that uses a rotary percussion type excavator having an outer casing 12 and an inner rod 14.

[0014] The outer casing 12 is cylindrical and rotates about an axis C1 to excavate the ground G with a cutting bit 16 at its tip. A well-known structure can be used for the outer casing 12. The example in the figure shows a case where the ground G is excavated diagonally downward to create holes for ground anchors, but the direction in which the ground G is excavated is not limited to this and may be, for example, horizontally or diagonally upward.

[0015] The inner rod 14 is a generally cylindrical shaft-shaped member provided generally coaxially within the outer casing 12. The direction of the axis C2 of the main body 24 of the inner rod 14 coincides with the direction of the axis C1 of the outer casing 12. The tip end 22 of the inner rod 14 bends toward the axis C3 from a bent portion 26 at the end of the main body 24, and a cutting bit 18 (cutting portion) is provided on the tip end surface 20. The angle θ between the axis C3 and the axis C2 of the main body 24 is an obtuse angle. Therefore, the tip end 22 of the inner rod 14 is formed in a dogleg shape when viewed from a direction perpendicular to the axis C2 of the main body 24. In this configuration, when the main body 24 rotates around the axis C2, the tip end surface 20 rotates around the axis C2 and moves across the entire range of the cross section within the outer casing 12. The cutting bit 18 on the tip end surface 20 can reliably cut the entire range within the outer casing 12.

[0016] The length L from the tip surface 20 to the dogleg-shaped bent portion 26 can be set appropriately depending on the construction conditions, etc., but may be set to, for example, about 0.5 to 1.0 m. The angle θ of inclination of the axis C3 of the tip side 22 with respect to the axis C2 of the main body 24 can be set appropriately depending on the inner diameter of the outer casing 12, the outer diameter and length L of the inner rod 14, etc., but may be set to, for example, about several degrees to several tens of degrees.

[0017] The tip end 22 of the inner rod 14 may be always bent in a V-shape, or may be always bent at an angle θ of 0° and deformed into a V-shape only during installation. Alternatively, a structure may be adopted in which the length L and angle θ are adjustable. In this case, the adjustment may be performed by remote control.

[0018] According to this embodiment, the tip side 22 of the inner rod 14 is formed in a dogleg shape, and by rotating this, the cutting bit 18 on the tip surface 20 can cover the entire area inside the outer casing 12, eliminating any areas that cannot be cut. This ensures that the entire area inside the outer casing 12 can be cut. Even when the inner rod 14 is affected by bending due to its own weight, cutting is possible throughout the entire area inside the outer casing 12, making it easier to reach the design depth. In addition, cutting is possible even in ground containing gravel of approximately 30 to 50 mm in diameter.

[0019] As explained above, the ground anchor installation method of the present invention is a method of installing a ground anchor using a rotary percussion excavator having a cylindrical outer casing that rotates about its axis to excavate the ground, and an axial inner rod that is provided inside the outer casing and rotates about its axis to cut the inside of the outer casing with a cutting section at its tip, wherein the tip side of the inner rod is formed in a dogleg shape when viewed from a direction perpendicular to the axis of the main body of the inner rod, and by rotating the main body about its axis, the tip side cuts the entire area inside the outer casing, so that the entire area inside the outer casing can be reliably cut.

[0020] Furthermore, the ground anchor installation device according to the present invention is a ground anchor installation device that uses a rotary percussion excavator having a cylindrical outer casing that rotates around its axis to excavate the ground, and an axial inner rod that is provided inside the outer casing and rotates around its axis to cut the inside of the outer casing with a cutting section at its tip, wherein the tip side of the inner rod is formed in a dogleg shape when viewed from a direction perpendicular to the axis of the main body of the inner rod, and by rotating the main body around its axis, the tip side can cut the entire area inside the outer casing, so that the entire area inside the outer casing can be reliably cut. [Industrial Applicability]

[0021] As described above, the ground anchor installation method and installation device according to the present invention are useful for installing rotary percussion type ground anchors, and are particularly suitable for reliably cutting the entire area inside the outer casing. [Explanation of symbols]

[0022] 10 Ground anchor installation equipment 12 outer casing 14 Inner rod 16,18 Cutting bits 20 Tip surface 22 Tip side 24 Main Unit 26 Bend C1,C2,C3 axis G Ground L length θ angle

Claims

1. A method for installing a ground anchor using a rotary percussion excavator having a cylindrical outer casing that rotates around its axis to excavate the ground, and an axial inner rod that is provided inside the outer casing and rotates around its axis to cut inside the outer casing with a cutting portion at its tip, A method for installing a ground anchor, characterized in that the tip side of the inner rod is formed in a dogleg shape when viewed from a direction perpendicular to the axis of the main body of the inner rod, and by rotating the main body around its axis, the tip side cuts the entire area inside the outer casing.

2. A ground anchor installation device using a rotary percussion drilling machine having a cylindrical outer casing that rotates around an axis to excavate the ground, and an axial inner rod that is provided inside the outer casing and rotates around the axis to cut the inside of the outer casing with a cutting portion at the tip, A ground anchor installation device characterized in that the tip side of the inner rod is formed in a dogleg shape when viewed from a direction perpendicular to the axis of the main body of the inner rod, and by rotating the main body around the axis, the tip side can cut the entire area inside the outer casing.

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