Self-anchorage Theory for Full Thread Screw Bolt and Relevant Application Test in Coal Mine Roadway

A new type of screw bolt with full thread and self-anchoring technology is presented. The rock-bolt dual coupling theory of this bolt was illustrated, the time-depended resistance increasing mechanism was revealed, and its ultimate supporting mechanism and relevant failure patterns in rock mass were further investigated. Additionally, pullout force and displacement relationship was compared and analyzed between traditional resin bonded bolt and the proposed bolt in followed engineering trial in Xiangshan Coal Mine, the obtained results proved that interlocking force and friction force were two main factors which contributed to the self-bolting effects of full thread screw spiral bolt, and the torque force applied during installation was a key factor determining the technical level of the full thread screw bolt.