Experiment on Cracks Dynamic Propagation Characteristics of Bedding Raw Coal in Static Blasting Damage

Using high definition camera, strain testing instrument and ZDKT-1 micro-seismic test system, we studied the crack propagation characteristics of raw coal samples when drillings are parallel and perpendicular to the bedding plane under the condition of slow static load. The results show that the cracks produced by drillings which are vertical to bedding plane static explosion damage show interchange expansion; cracks produced by holes which are parallel to the bedding plane are only along the bedding plane expansion; during the static explosion, the borehole surface strain gauge is subjected to tensile load first under compression load, and the strain gauge with the drilling depth of parallel plane vertical and parallel direction is only subjected to tensile loading. The closer of the static explosion process to the strain signal is, more frequent of the micro-seismic events are.