Pipe bolt

The pipe-type anchor bolt is a novel anchor bolt for full-length anchoring and active reinforcement of the surrounding rock. Its three-dimensional part is a high-strength steel pipe with longitudinal slots. When installed in a borehole slightly smaller than the pipe diameter, it can immediately apply radial pressure and frictional force to prevent the surrounding rock from slipping, along with the supporting force of the anchor bolt plate. This keeps the surrounding rock in a state of three-way stress, thereby greatly enhancing the rock strata. In situations such as blasting vibration and anchor displacement of the surrounding rock, the later anchoring force significantly increases. When the surrounding rock undergoes significant displacement, the anchor bolt does not lose its supporting resistance, and it possesses superior characteristics compared to the expanding shell anchor bolt.

Specs

1. Outer Diameter (mm): Φ30, Φ33, Φ40, Φ43 (±0.5)

2. Length (mm): 1200, 1500, 1800, 2000, 2500; Material: Q235, 16Mn, 20MnSi.

Working Principle

Install the tube-shaped anchor bolts in holes slightly smaller than the tube diameter. In this case, three forces are exerted on the surrounding rock: radial pressure across the entire length of the tube-shaped anchor bolt on the hole wall, friction to prevent the surrounding rock from sliding, and the supporting force from the anchor bolt's plate. These three forces make the surrounding rock more stable.

Technical Features

1. Raw materials are made of high-strength alloy strip steel.

2. Easy installation;

3. No need for anchoring agent.

4. The anchor rod has a high friction with the rock mass.

5. High shear and tensile strength.

6. Equipped with high-strength trays, ensuring even distribution of load.

7. Tunnel height exceeds anchor rod length.

Technical Specifications

1. The surface of the pipe anchor bolts should be smooth, free of severe scratches and rust. Welds should be free of cracks, voids, and slag, and it is not allowed to burn through the pipe wall. The tray should be able to move freely on the rod body. The挡环interface and the pipe seam opening should ideally be misaligned by 170o-190o.

2. Retaining ring weld seam tensile pull-out force ≥ 80kN, rod body ultimate tensile strength ≥ 110kN, initial anchoring force ≥ 25kN/m, tray bearing capacity ≥ 65kN.

Technical Performance

Initial Anchor Pull: 3~7 tons

2. Tubing collar pull-out load: 8~10 tons.

3. Anchor rod tensile break resistance: 12~13 tons.

4. Corrosion resistance is 20~30% higher than A3 steel, beneficial for long-term use.

Usage Instructions

1. Determine the anchor bolt hole positions based on design requirements and drill holes using drilling equipment.

2. Blast away the rock dust inside the holes with compressed air.

3. Install the anchor plate on the rod, then hammer the anchor bolt into the hole with an impact drill.

Recommended calculation method for the borehole diameter of tubular bolt anchors:

In the rock strata: Borehole diameter = (0.9-0.95) × Anchor Rod Diameter; Anchor Rod Borehole Depth: Anchor Rod Length + 100mm; Borehole Deviation Rate < 1%

In the coal seam: Drilling diameter = (0.9-1.00) × bolt diameter Bolt drilling depth: Bolt length + 200mm Drilling deflection < 1.5% [1]