Which formations are self-drilling bolts suitable for?

Generally speaking, the self-drilling bolt is suitable for the stratum, the bolt retaining wall, and the soil nail wall.

For anchoring technologies that require drilling operations, drilling often becomes the most critical process and directly affects the bearing capacity of the bolt. Drilling in relatively loose and groundwater-affected strata, the phenomenon of hole collapse is common, requiring casing follow-up to increase the difficulty and cost of construction. The casing improves the drilling progress, but has an adverse effect on the bond between the mortar and the hole wall. After the loose formation and the rock formation with many pores and open cracks are formed, high-pressure grouting can compensate for the geotechnical defects. In this case, the consistency of the grout needs to be adjusted properly so that the mortar fills the cracks to ensure the quality of the bolt.

Self-drilling bolts are most suitable for pebble and boulder formations. After drilling, grouting can effectively reinforce the disturbed part of the rock and soil around the borehole, and expand the diameter of the anchor. If there is a small amount of water seepage during the drilling process, it will also be It can be done by blowing dry cement powder into the hole with high pressure air. Form temporary retaining walls around boreholes to reduce hole collapse.

At present, most of the anchor rods (including soil nails) and pre-stressed anchor cables are manufactured on site, and their production methods and processes directly affect their quality. Rods - grouting and compensation grouting – pre-stressing - fixing and end treatment. The pre-stressed anchor cable is composed of multiple bundles of steel strands. The application of pre-stress requires special equipment, and the construction quality varies greatly, while the complete set of self-drilling anchor rods is factory-produced, which reduces the need for anchor rod production and anchor rod installation. This process can increase the bearing capacity by 25% only by tightening the bolts by applying pre-stress, with reliable quality and improved work efficiency.