Rock dynamic fracture by destress blasting and application in controlling rockbursts in deep underground

Abstract

Destress blasting is regarded as an active mitigation measure for preventing rockbursts in deep underground works, whose mechanism and effectiveness, however, have still been in debate. A self-developed combined finite-discrete element method software is implemented in this study to first model the rock fracture process induced by a single-hole destress blasting based on a practical blast in a deep gold mine with high in-situ stresses. The effects of accelerometer holes and bedding planes are discussed. Then, a two-round tunnel face excavation in deep underground with high in-situ stresses is modelled, which reproduces the occurrence of the excavation-induced rockbursts. Finally, destress blast-holes are introduced into the same model prior to the two-round tunnel face excavation to investigate the effect of the destress blasting on the excavation-induced rockbursts. It is found that the fractures induced by the destress blasting shift the high abutment pressure induced by the excavation away from the tunnel face and then protect the tunnel wall from fracturing. The numerical modellings reveal that the success of the destress blasting in controlling excavation-induced rockbursts depends on not only the site condition but also the design of the destress blasting such as the arrangement of the blast-holes and the explosive charges.