Experimental and numerical study of failure behavior and mechanism of coal under dynamic compressive loads

A comprehensive understanding of the failure behavior and mechanism of coal is a prerequisite for dealing with dynamic problems in mining space. In this study, the failure behavior and mechanism of coal under uniaxial dynamic compressive loads were experimentally and numerically investigated. The experiments were conducted using a split Hopkinson pressure bar (SHPB) system. The results indicated that the typical failure of coal is lateral and axial at lower loading rates and totally smashed at higher loading rates. The further fractography analysis of lateral and axial fracture fragments indicated that the coal failure under dynamic compressive load is caused by tensile brittle fracture. In addition, the typical failure modes of coal under dynamic load were numerically reproduced. The numerical results indicated that the axial fracture is caused directly by the incident compressive stress wave and the lateral fracture is caused by the tensile stress wave reflected from the interface between coal specimen and transmitted bar. Potential application was further conducted to interpret dynamic problems in underground coal mine and it manifested that the lateral and axial fractures of coal constitute the parallel cracks in the coal mass under roof fall and blasting in mining space.