JPS60115800A - Grout anchor construction method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a grout anchor method in the NATM method and the like.

Prior Art In the conventional grout anchor construction method, a construction method as shown in FIG. 4 has been adopted.

In other words, especially in a hole a formed upward in the ground, until the fixing grout b is completed and a certain strength is developed,
It is necessary to temporarily support and fix the stress transmitting material C inserted into the drilled hole a. For this purpose, a method is adopted in which a packer d is attached to the opening side of the drilled hole a to provide temporary support.

If such a method is used, it becomes very difficult and complicated to recover the hole drill casing e, and in some cases, the casing e may be left buried, leading to an increase in construction costs.

In addition, when a PC strand is used as the stress transfer material C, if the opening side of the drilled hole a of the PC strand is temporarily fixed, the PC
When the strands become sagging, twisting occurs at the same time, and if grout is injected and fixed without eliminating the slack and twisting, the elongation of the stress transmitting material will not be as designed, and the twisting will cause uneven pressure on the transmitting material. may come into play.

Purpose of the Invention This invention was made to solve the above-mentioned problems. It is possible to reduce the construction cost, it is possible to expect the stress transmission material to elongate as designed, and the stress transmission material can be expanded by lateral pressure. The purpose is to provide a grout anchor construction method that can prevent the breakage of grout anchors.

Composition of the invention The grout anchor construction method according to this invention is as follows.

A PO strand with a catching packer attached to the outer periphery of the anchor cable is temporarily fixed in the drilled hole, grouting material is injected around the outer periphery of the anchoring part of the anchor cable, and then grout is applied to the outer periphery of the free length while the free length is extended. The above objective is achieved by injecting the material.

EXAMPLE Hereinafter, the present invention will be explained in detail based on an example shown in the drawings.

In FIG. 1, reference numeral 1 denotes a po strand, which is a stress transmitting material, on which an anchoring section 2 having a convex and concave shape with a tip is formed, and a free length section 4 from the proximal end to the distal end of the anchoring section 2 is inside the sheath 3. The anchor cable A is configured by being inserted into the anchor cable A.

This anchor cable A is inserted into a hole B formed in the ground of the tunnel. There are various methods of insertion, but one is to insert a coupling at the end of anchor cable A.
It is conceivable to insert the anchor cable A by pulling the coupling toward the drilling side using a steel cable and pushing the entire anchor cable A up.

A catching packer 5 is attached in advance to the outer periphery of the anchor cable A between the fixed part 2 and the free length part 4. Various configurations can be adopted as the catching packer 5, but for example, a configuration in which a cloth soaked in cement milk and made plain is wrapped around it can be adopted. With such a catching packer 5, moisture will be extracted in the hole B, and the cement milk will harden and adhere to the ground in the hole B, and the deeper part of the hole B than the catching packer 5 will be sealed. I will do it.

As described above, the anchor cable A is temporarily fixed by the catching packer 5. If drilling hole B is formed upward, attach coupling 6 to the end of anchor cable A.
The coupling 6 is suspended by a wire 7 fixed to the earth to support the anchor cable A, and wait for the catching packer 5 to harden and be fixed to the earth.

Grout material 8 is injected from the tip of the anchoring part 2 of the anchor cable A, and is filled between the outer periphery of the anchoring part 2 and the ground. After the grout material 8 has hardened, the coupling 6 is removed and the hole B is drilled.
If the casing 9 used for forming is left behind,
The casing 9 is removed.

The fixing section 2 of the anchor cable A is fixed as described above, but the free length section 4 is in an extended state.

Grout material 8 is injected into the outer periphery of the sheath S. If the drilled hole B is facing upward, the free length portion 4 will be free of sagging and twisting simply by removing the coupling 6, but if necessary, it may be slightly tensed due to jerking etc. to eliminate the sagging and twisting. be.

A packer 10 is installed between the outer periphery of the end of the anchor cable A on the opening side of the drilled hole B and the earth, and the space between the outer periphery of the free length portion 4 and the earth is sealed. Grout material 8 is injected into the space, and after hardening, the PC strands 1 are tensioned to complete the construction.

Effects of the Invention Since the grout anchor construction method according to the present invention has the above configuration, it is possible to obtain the following effects.

■ Since it is possible to fix only the fixing part first and remove the casing easily, construction can be made at low cost.

@ Only the anchoring part is anchored first, and the free length part can be anchored in an extended state, eliminating sagging and twisting, allowing the stress transmission material to stretch as designed, and preventing lateral pressure from occurring. and will not cause breakage.

[Brief explanation of the drawing]

1 to 3 are longitudinal cross-sectional views of the construction sequence of the grout anchor method according to the present invention, and FIG. 4 is a longitudinal cross-sectional view of the conventional grout anchor method. A... Anchor cable% B... Hole drilling, 1... PC strand, 2... Anchoring part, 3... Sheath, 4... Free length part, 5... Catching packer, 6... Coupling,
7. Wire, 8. Grout material, 9. Casing, 10. Packer.

Claims (1)

[Claims] In a grout anchor construction method in which a free length of a PC strand is inserted into a sheath and an anchor cable with a protruding anchoring part at the tip is anchored in a hole formed in the ground, A catching packer is attached to the outer periphery between the free length part and the anchorage part and inserted into the drilled hole, the anchor cable is temporarily fixed by the catching packer, grout is injected between the outer periphery of the anchorage part and the ground, and then the free length part is This grout anchor construction method is characterized by attaching a backer between the outer periphery of the end of the anchor cable on the drilling opening side and the ground in a stretched state, and injecting grout material between the outer periphery of the free length and the ground to fix it.