How Do Self-drilling Hollow Bolts Support the Broken and Loose Rock?

Self-drilling hollow bolts were first used in American coal mines in the 1970s and began to be used in my country in the late 1980s. In recent years, it has been used more and more in deep foundation pit support engineering. Because of its fast construction speed and good anchoring effect, it is gradually replacing traditional steel anchor rods and seamless pipe anchor rods, self-drilling hollow anchors. The rod reinforcement mechanism is as follows:

The self-drilling bolt is mainly composed of a hollow bolt body, a nut, a backing plate, a connecting sleeve, and a drill bit. The surface of the hollow bolt body has the same thread as that of the drilling tool, which can be directly connected with the output end of the drilling rig to realize the self-drilling bolt. of drilling.

During the drilling process of the self-drilling hollow bolt, the hollow bolt body doubles as a drill pipe and a medium transmission channel, and finally acts as a reinforcement body for geotechnical support. When drilling into the rock formation, compressed air or water can be introduced, and the drilled rock debris can be flushed out of the hole by the air or water, and finally injected into the cement slurry for anchoring; in the soil stratum, the cement slurry can be directly injected, while drilling While grouting, on the one hand, the cement slurry can discharge the drilled soil debris out of the borehole, on the other hand, it can consolidate the loose hole wall, prevent the hole from collapsing, and thus play a better anchoring effect.

In short, the self-drilling bolt adopts a one-time hollow bolt body, drill bit, connecting sleeve, and other structures. After connecting the drilling rig, it can be drilled directly. After drilling, it can be directly grouted or injected while drilling without pulling out. After the slurry solidifies, the hollow bolt body is left in the hole and acts as a reinforcing body to play a supporting role, that is, the mechanism of the self-drilling hollow bolt is the integration of drilling, grouting, and anchoring, so its construction speed It is fast and has good anchoring effect, and can also be used for special geology with easy-to-collapse holes.