Analysis of bolting failure in deep mining roadway and support countermeasures

Aiming at the problem of bolt support failure caused by surrounding rock deformation in deep mining roadway,a method was proposed to reduce the bolt breakage by improving the bolt stress state, changing the anchoring mode and optimizing the shape of rod body. On this basis, a new rebar anchor rod with a new shape and structurewas designed. Laboratory tests show thatthe average pull-out force of the right-hand bolt, the left-hand bolt and the high strength bolt with large rib spacings are 136.9 kN, 106.1 kN and 147.6 kN, andthe large-rib spacing high-strength bolts absorb energy better result. Before the field test, the surrounding rock structure of the return air roadway was detected, including roof drilling and loose circle testing. The final roadway support scheme was determined according to the detection results of surrounding rock structure. The original supporting scheme and full bolt supporting scheme were adopted for the return roadway, and the roof separation and bolt stress were monitored in real time. The test results show that the maximum roof subsidence of roadway supported by high-strength bolt with large rib spacing is reduced by 36.4% compared with the original support scheme, and the roof separation amount is reduced by 24.1% compared with the original support scheme. The results of the stress on the roof and two side bolts show that the stress of high-strength bolt with large rib spacing is smaller than that of the original support scheme, and the maximum stress of roof bolt is 442.9 MPa and 78.1 MPa respectively, and the improved scheme is reduced by 82.4% compared with the original support scheme. At the same time, compared with the original support scheme, the failure of bolt support is significantly reduced, which indicates that the full-length anchored high-strength boltwith large rib spacingis more conducive to maintain the stability of roadway.