Application of Self-drilling Hollow Grouting Bolt in Roadway Bulging Treatment

by Anna S. Optimization Specialist

The section of the inner water silo roadway of a coal mine is designed as a straight wall semi-circular arch, and the excavation section is 3840mm wide and 2920mm high. The original design was anchor mesh and spray support, and then it was optimized for reinforced concrete masonry support, and the bottom plate was paved with concrete. After the roadway was used for one year, a large area of ​​kick drum appeared, and the maximum volume of the kick drum was 900mm, which seriously affected the volume of the water tank and the safety of the roadway.

Cause Analysis

Judging from the on-site damage situation, the bottom bulge of the inner silo roadway is mostly after the pressure of the surrounding rock on the roof is transmitted to the bottom plate. Because the mudstone of the bottom plate is relatively broken, it cannot effectively support the transferred pressure and is transmitted to the coal seam with a thickness of about 900mm below the bottom plate, which is caused by the compression of the coal seam.

Construction Method

According to the situation of the bottom drum in the roadway of the inner water silo, and considering that the rock fissures are relatively developed, it is determined that the anchoring support technology is used to control the bottom drum, and the self-drilling hollow grouting bolt is used. The anchor rod is anchored with resin at the end, and the rod body is made of seamless steel pipe or high-strength steel pipe, with a specification of jb25mmx2 500mm; the rod body is distributed with slurry diffusion holes. After the grouting pipe is connected to the tail of the rod body, grouting can be carried out.

Grouting Design

The grouting material is a single-liquid cement slurry with a water-cement ratio of 0.8 to 1.0.

(1) The depth of the grouting hole. It matches the length of the hollow bolt, which is 2.4m.

(2) Grouting pressure. There is basically no hydrostatic pressure in the surrounding rock, and the grouting pressure only needs to overcome the resistance of the slurry flow, and at the same time

Make the slurry spread too far to avoid wasting grouting material. According to this requirement, the grouting pressure is determined to be 1.0-1.5MPa, and the maximum grouting pressure is 2MPa.

(3) Slurry diffusion distance. Generally controlled within the range of 1 ~ 3m. The front of each shift is used to drill the bolt eye and install the bolt; the rear (20-30m from the working face) is used for grouting, and the interval grouting method is adopted.

Construction Technology

1. First use the pickaxe to brush the two gangs and undercover agents in the big roadway, and clean the bottom plate. The broken concrete blocks, gangue and floating coal excavated by brushing are loaded into the 1.5t U-shaped mine car and lifted to the ground through the auxiliary shaft for discharge.

2. Then pour 300mm thick concrete reverse arch. After the anti-bottom arch concrete reaches the design strength, drill the bolt hole and install the self-drilling hollow grouting bolt according to the design requirements.

3. When installing the anchor rod, use an 18mm threaded steel ladder beam to fix the anchor rod.

4. After the bolt is installed, use the exposed bolt hole to grout and reinforce the surrounding rock at the bottom. The grouting is carried out from the inside to the outside, and the left and right operations are performed in sequence. First, grout the bolts according to the row spacing of 2.0m; after grouting for 20m, then return to insert the grouting, and the row spacing is also 2.0m. Each section is filled with bottom corner anchors first, and then bottom anchors; while installing the anchors, install reinforced ladder beams and pre-tighten the anchors; after grouting, tighten the anchor nuts and backing plates.

Support Effect

After reinforcement and treatment with self-drilling hollow grouting bolts, the floor of the roadway has been stable, and no bottom bulging occurs again. This fully shows that the self-drilling hollow grouting bolt has a very good supporting effect on the soft rock under complex conditions.

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Created on Aug 4th 2022 02:04. Viewed 102 times.

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