Longitudinal Slit Type Concrete Sleeve Anchor φ43

Details of Pipe Seam Anchor

A slit-tube metal anchor is a type of anchor manufactured by means of rolling and pressing sheet metal into a tubular rod with longitudinal slits. It can be drilled through a rock drill into a hole smaller than the diameter of the anchor to apply direct radial pressure and create resistance through the layers to prevent sliding of the surrounding rock. At the same time, the anchor tray pallet provides additional support. In this way, the surrounding rock can be subjected to three-way forces simultaneously, resulting in a frictional anchoring force created by the elastic tension of the 

pipe wall squeezing the rock formation. This anchoring force is analogous to the way expansion nails securely hold a stratified rock formation in the surrounding stable rock. The pressure exerted into the borehole by each meter of anchor is approximately 25kN, producing an anchoring force roughly equal to the pressure. The thicker the wall of the anchor, the higher the elastic stress in the metal tubing, the less compression of the borehole and the greater the anchoring force, given the same outer diameter and material of the anchor. In hard rock strata, the anchoring force of anchor rods is greater, for example, in sandstone, the anchoring force can reach 60~100kN. at the same time, after the rock strata undergoes blasting vibration or after a period of time, the later anchoring force will increase significantly. In coal strata, after 100 days of installation, the anchoring force can be increased from 60kN to 90kN. anchor rods can also adapt to the lateral anchoring movement of the strata and have better bending adaptability, so that the anchoring effect is more solid even if the drill hole becomes bent.

Specifications and parameters

Main Specifications: MF43 MF40 MF33

Length (mm): 1200, 1500, 1800, 2000, 2500

Material: Q235, 16Mn（Q345  Q355）, 20 Mnsi.

Principle of Operation of Slit Tube Anchor

It is through the use of longitudinally slit high-strength steel pipe, installed in a drill hole slightly smaller than the diameter of the anchor, immediately applying radial pressure over the full length and friction to stop the surrounding rock from sliding down, as well as the bearing force of the pallet pallet. This puts the surrounding rock in a state of three-way force and enables the later anchoring force to increase significantly in the event of blasting vibration or displacement of the surrounding rock. Even if the surrounding rock is significantly displaced, the anchor still has the support resistance, and has better characteristics than the rising shell type anchor.

The method of using the sewing tube type anchor is as follows:

1.Determine the hole position of the anchor according to the design requirements and use the drilling rig to drill the holes.

2.Use the pressure fan to blow out the rock dust in the hole.

3.Install the body of the anchor rod on the anchor disk and use the impact drill to drive the anchor rod into the drilled hole.

The diameter and depth of the drilled holes can be determined based on the following calculations:

In the rock layer, the diameter of the drill hole is 0.9-0.95 times of the diameter of the anchor rod, the depth of the drill hole is the length of the anchor rod plus 100mm, and the deflection rate of the drill hole should be less than 1%.

In coal seams, the diameter of the drill hole is 0.9-1.0 times the diameter of the anchor rod, the depth of the drill hole is the length of the anchor rod plus 200mm, and the skewness of the drill hole should be less than 1.5%.

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