CT scanning 3-D fracture Acceleration factors Acoustic emission Backfill mining BiOBr BiVO4 Cement grout Coal gasification Coal measure rocks Coal seam overlain by thin bedrock and thick clay layer Combined early warning method Contraction factor Control technology Deep coal mine Direct shear test Drilling cutting method Electromagnetic emission Energy Band Structure Excavation disturbance Field measurements Filling ratio Fracture characteristics Half-coal-rock roadway High temperature Island coal face Mechanical criteria Mechanical optimum design Mesoporous microsphere Methyl Orange