Experimental and numerical study on directional rock fracture induced by a composite shaped charge liner

Crack propagation in rock blasting exhibits strong randomness, making directional fracture control difficult and leading to low energy utilization efficiency, which remains a key issue in controlled blasting. To improve the energy utilization efficiency in directional fracturing, a composite shaped charge liner with a “slotting + shaped-charge” structure was designed. A combination of dynamic caustics experiments and numerical simulations was employed to investigate the effects of liner opening angle on crack propagation and energy release. In the experimental study, dynamic caustics technique was used to capture the initiation and evolution of cracks under blasting loading, and key dynamic parameters such as crack propagation velocity and stress intensity factor were obtained from caustic patterns. Meanwhile, fractal dimension analysis was introduced to quantitatively characterize the complexity and directional distribution of blast-induced cracks. In the numerical study, a fluid-structure coupled model was established to simulate the blasting process, enabling further analysis of stress wave propagation, energy release behavior, and the formation and penetration characteristics of the shaped charge jet under different opening angles. The results show that the composite shaped charge liner significantly enhances crack propagation in the energy-focused direction while suppressing damage in non-focused directions. The shaped-charge effect first increases and then decreases with increasing opening angle. When the opening angle is 60°, the crack propagation length, propagation velocity, the ratio of fractal dimensions between focused and non-focused directions, and the dynamic stress intensity factor all reach their peak values, indicating the optimal directional fracturing performance. The energy release rate increases with the opening angle and reaches 746.05 N/m at 75°. Numerical simulations indicate that, at an opening angle of 60°, the formed metal jet exhibits the most coherent morphology and the highest jet-tip velocity, with the penetration depth and inlet aperture reaching 21.5 mm and 14.1 mm, respectively.