Analysis of the Mechanical Properties of Fractured Rock Masses Under Dynamic Loading Conditions

Hard roof strata that fail to collapse timely often create large overhangs, which can trigger severe roadway deformation and dynamic disasters. To weaken such hard rock masses, deep‐hole blasting precracking is commonly applied. This study investigates the impact failure characteristics of prefractured rock masses using split Hopkinson pressure bar (SHPB) experiments on cement mortar specimens with artificial cracks, complemented by LS‐DYNA numerical simulations. The results show that the peak strength of the specimens decreases with increasing crack length, crack area, and crack thickness. Moreover, a larger crack volume leads to higher energy dissipation and lower transmitted energy. Under impact loading, cracks first propagate along the preexisting fracture direction until they penetrate the entire specimen; subsequently, wing cracks develop from the main crack tips, and finally the specimen is fragmented by the shock wave.