Failure mechanism study on tail of high strength bolt.

Aiming at the problem that many high-strength rock bolts fail at the thread part without obvious decrease in diameter, analytical analysis on the stress status of the thread was performed. The results show that stress concentration due to the change in diameter and self-locking of the domed washer due to inappropriate rotation center of the washer worsen the mechanical status of rock bolts. Laboratory tests on fractured threads was carried out, chemical analyses were performed on the fractured threads, the effect of the varied installation angles on the bending fracturing of rock bolts was tested. The mechanical status and the stress distribution in the thread was carried out using finite element method,and the most unfavorable position of the rock bolts was identified. Field tests were performed in the roadways suffering severe dynamic mining-induced stresses in the Zhangcun Coal Mine, many optimization plans were proposed to solve the rock bolt fracturing issue and to relieve the effects of the unfavorable forces on the rod of rock bolts. [ABSTRACT FROM AUTHOR]