Dynamic expansion rock bolt for rapid installing in rocks

Rock bolts are used as permanent and temporary support systems in tunneling and mining operations. A dynamic-expansion rock bolt system that can be installed rapidly in a drilled hole is introduced in this article. The dynamic-expansion rock bolt system consists of a star-shaped steel tube and an ignition system with a dynamic expansion agent in the steel tube of the rock bolt. After the ignition of the dynamic agent in the tube, the star-shaped steel tube expands dynamically as a result of gas production by the dynamic agent. This expansion leads to frictional mounting of the tube in a drilled hole. Laboratory-scale pull-out tests of the rock bolt, installed in a thick steel tube, were performed to investigate the friction behavior between the steel tube and the smooth wall of a drilled hole. These tests revealed that the ultimate pull-out load reached approximately 6 kN and that a long displacement subsequently occurred. Field-scale tests for two prototype rock bolts were performed to evaluate the pull-out load-bearing capacity of the rock bolt. The welded areas of the two tube bolts were broken when the pull-out loads reached approximately 114 and 91 kN.