Four steps to note in mining anchor construction

I. Anchor material

Prestressing anchors should use steel wire, high-strength steel wire or high-strength threaded steel bar. Anchor and coupling anchor rod body is required to withstand more than 95 anchor rod body limit tension.

Mining anchor casing when the plastic casing is used, it is required to have sufficient strength, water resistance and chemical stability.

The anti-corrosion material of the anchor rod should not crack, become brittle or soften into fluid under working conditions. No adverse reaction with the anchor solid and surrounding materials, chemical stability and water resistance.

Anchor grouting materials should be used ordinary silicate cement and particle size less than 2mm in fine sand fine aggregate.

2.Anchor hole formation

General requirements of the anchor hole is not less than the design length should not be greater than the design length of 1, hole error should not be greater than 50mm (horizontal) and 100mm (vertical), tilt size deviation should not be greater than the length of the anchor.

Geological drilling rigs and auger drilling rigs are preferred for hard soil layers, and soil anchor drilling rigs with wall casing are preferred for saturated clay and soil layers prone to collapsing holes.

Commonly used anchor construction equipment. After the hole is made, the drilling rod should be pulled out immediately, the prestressing tendon should be inserted, and then the casing should be pulled out.

3.anchor tendon setting and grouting

Anchor manufacturers when the anchor bar using steel wire or high strength steel wire, should be uniformly straight discharge, along the axis direction of the rod every 1.0 ~ 1.5m set up - an isolation frame, the protective layer of the rod should be less than dry 20mm, pre-stressing tendons (including exhaust) should be bundled, firm, non-anchored section of the anchor bar that is the free section of the plastic pipe should be wrapped, and the anchored section of the plastic pipe pipe intersection of the pipe four should be sealed and tied with aluminum wire.

The design strength of the grouting body should not be less than 20MPa Anchor grouting process has two kinds of primary grouting process and secondary grouting process.

4.tensioning and locking

Before tensioning, the first thing is to calibrate the tensioning equipment, when the anchor solid and pedestal concrete strength are greater than 15MPa should be able to carry out tensioning.

Anchor tensioning should be carried out according to the procedure, pay special attention to the order of anchor tensioning, should consider the interaction of neighboring anchors. Pre-tensioning should be carried out 1~2 times before anchor tensioning, taking 0.1~0.2N, (design axial tension), in order to check whether the process is properly prepared.

Anchor tension control stress should not exceed 0.6fom, temporary anchor tension control stress should not exceed 0.65fw. When tracing samples tensioned to 1.1~1.2N, sandy soil should be kept for 10min, cohesive soil should be kept for 15min, and then unloading rare locking load locking.