Study on rock damage and failure depth under particle water-jet coupling impact

•Analysis of dynamical damage process by establishing simulation model of particle water-jet coupling impact rock.•The effect factors of rock damage and failure depth were discussed with experiment and simulation.•The failure mechanism and damage expansion law were revealed by defining Gaussian points. Aiming at the problems of difficult observation of rock damage mechanism and many influencing factors of rock-breaking process, the damage mechanism of particle water-jet coupling impact was studied. Based on SPH-FEM coupling algorithm, the numerical model of particle water-jet impact rock was established, and the mechanical properties of rock were characterized by JH-2 (Johnson Holmquist II) damage model. Then, damage evolution and failure effect under the impact of water-jet and particle water-jet were simulated. It shows that the failure of rock is a cyclic process of “damage–cumulative damage–failure–cumulative damage–failure”, which is mainly manifested as shear powder and tensile cracks. Meanwhile, particle water-jet coupling impact rock-breaking experiment system and methods were introduced and the comparison way of experiment and simulation was used to analyze the influence law of particle ratio, water-jet impact velocity, particle diameter, impact angle on rock damage and failure depth. The propagation law of transverse and longitudinal damage inside of rock was studied by defining Gaussian points and damage would often occur instantaneously which was basically microsecond level.