Fractal characteristics and fracture mechanisms of flying gangue in longwall workings of the steeply dipping seam

The flying-gangue hazard has long threatened the safety of personnel and mining equipment in steeply dipping/inclined coal seams. A flying gangue maybe produces a large number of “subgangues” after impacting on the longwall floor, it’s damage is sharply increased. Revealing the rupture response and fragmentation mechanism of the flying gangue under dynamic loading is one of the important contents to grasp the characteristics of dynamical damage for flying gangue hazard. This study was carried out through the combination of Split Hopkinson Pressure Bar test, model test and numerical simulation test. The results show: The failure mode of coal-rock under high-speed impact can be divided into three types: intact, single crack, and severe fragmentation. Fractal dimension D the coal specimen has a logarithmic relationship with the strain rate. Coal with lower uniaxial compression strength is more severely broken and has a larger fractal dimension D under the same strain rate conditions. The larger the coal size, th