The application of self-drilling anchor hollow bar in slope supporting

Abstract

Self-drilling hollow grouting anchor is a new type of anchor bolt. In contrast to conventional mortar anchor construction, self-drilling anchoring is faster and can achieve better performance. What’s more, it is also easy to install self-drilling anchors.

The application of self-drilling hollow grouting anchor reinforcement slope technology is introduced in the case of side-slope support in the secondary hydropower station rock broken dam left abutment and the entrance of power generation tunnel.

Keywords

Self-drilling hollow grouting anchor, slope support, hydropower station.

Project Overview

The two-grade hydropower station is located in Xinjiang Kashi River. Its main task is to generate electricity, followed by the upstream cascade hydropower station has a certain anti-regulation task. It is concrete gravity dam, the maximum dam height is 33.8m, power plant installed capacity is 50MW.

The slope is divided into left abutment slope and power generation hole entrance face slope. The left abutment slope for the bedrock mountain, partially covered with a small amount of quaternary collapse slope plot of gravel and gravel soil. The diversion tunnel hole face sloping gate well is the slope gravelly soil, the thickness is about 6.5m. The structure is loose. After the excavation of the power hole entrance hole face, due to slope rock mass is extremely broken and serious weathering, leading to the hole face block collapse phenomenon.

Application of self-drilling hollow grouting bolt

1. Design of self-drilling hollow grouting anchor reinforcement

   1.1 Features

Self-drilling hollow grouting bolt with good thick-walled seamless steel pipe material, the perfect surface of the thread forming process and well-crafted accessories, is a kind of new type of anchor rod which is used to drill hole, bolt installation, grouting, and anchoring.

It can be cut or connected according to the needs of the project. The construction is very convenient. The bolt body of the drill pipe does not need to be pulled out, and space can be used as grouting channel to grout from the inside to the outside, which avoids the mortar loss caused by the traditional grouting pipe pulling out.It can improve the anchor grouting density, thereby increasing the rock bolt and rock binding force and durability of the bolt.

Self-drilling hollow grouting anchor has the characteristics of fast construction speed, good anchoring force, simple operation and timely supply of anchor force.

As the result of this kind of bolt three-in-one function makes it in all kinds of rock conditions under construction, without casing, pre-grouting or other special methods can also form anchor hole and ensure the anchoring and grouting effect.

1.2 support design

1. slope stability analysis

   In the dam left abutment and power hole entrance hole face rock broken slope, soil slope, and other parts, self-drilling hollow grouting bolt is used on the excavation slope for timely support. It avoids the collapse of the impact of the construction to ensure the stability of the excavation slope.

2. design parameters of slope support

   R32, Length=4.5m Self-drilling hollow bar anchor with steel mesh spray protection for the sloped support.

3. the design of slurry mix

   The grouting slurry should be mixed with water, cement, expansion agent and quick-setting agent.

4. the design of self-drilling hollow grouting bolt support

   Grouting through the hollow bolt body. Grouting progress should be uniform.

    

   2. Construction of self-drilling hollow grouting anchor

   2.1 Boring and installation of anchor bolt

   1. Self-drilling hollow grouting bolt installation procedures: first install the bolt, and then grouting.

   2. Check the hole in the bolt body, drill bit water hole. If any hole is blocked, it should be cleaned up.

   3. Inspect the connections of the drill bit and the anchor rod, the rock drill and the shank, the drill connection sleeve and the shank, and the bolts and rig connections.

   4. The hole diameter for self-drilling hollow grouting anchor is 50mm. According to the design requirements of the hole angle and hold to adjust the drill rig.

   5. Start drilling.

   6. At the end of the drilling, clean the dust with a wind gun and check for holes in the drill bit before removing the anchor from the rig connection.

   7. Ready to grout.

   2.2 Injection

   1. Grouting with an injection machine.

   2. Use air to detect whether the bolt hole is clear.

   3. Grouting.

   4. 14 days after grouting completed, take the face of the concrete construction.

3. Quality inspection of self-drilling hollow grouting bolt

   3.1 The quality of grouting

   The quality of grouting is mainly whether the compressive strength meets the design requirements. Guarantee rate was 100%.

3.2 Anchorage force of anchor bolt

14 days after grouting completed, according to the rated load of the anchor bolt, 25 anchor rods were taken for the pulling test. Guarantee rate was 100%.