Characterization of Tensile Crack Propagation and Energy Evolution during the Failure of Coal–Rock Samples Containing Holes

The instability and fracturing of gas drainage boreholes are one the main causes low efficiency. Based on rock mass energy principle Barenblatt model, evolution coal–rock around hole, conversion characteristics dissipated Ud, propagation pattern initial tensile cracks were investigated. results show that based process energy, failure samples containing holes can be divided into an dissipation stage, a decelerated stable accelerated stage. is always greater than elastic during first half loading, it mainly used for continuous development cracks. Then, remote to left right hole boundary generated inhibit Later, when storage limit reached, strain released, macroscopic propagate coalesce, which stress environment change reopen finally propagate. in upper lower ends undergo opening–closing–reopening process, presence cohesion c(x) hinders formed by generation migration fracture initiation zone, friction intact zone. released was related different stages crack propagation, could structure monitoring flaw predicting borehole.