Theoretical modeling and experimental study of rock-breaking depth in particle jet impact drilling process

Particle jet impact drilling technology is an efficient method to improve rock-breaking speed by high-speed particles and water-jet impact. The process and damage stage of rock-breaking by combined impact of highspeed water-jet and particles are very complicated, therefore, it is of great significance to study the rock-breaking depth in different damage stages for particle jet impact drilling. Therefore, laboratory test was carried out to study the effects of rock breaking depth on particle diameter, impact velocity and particle mixing ratio. Then, the semi-analytical model of rock-breaking depth under particle jet impact was established in stable damage condition, and the effect factors of rock-breaking depth were numerically analyzed. Based on SPH-FEM coupling algorithm, the dynamical simulation model of particle jet impact rock was established, and the simulation of rock-breaking process and damage evolution under particle jet impact was carried out. Effects of different particle jet parameters on rock-breaking depth were studied by comparing the semi-analytical mode calculation, dynamic simulation and experimental results. Analysis results showed that rock-breaking depth by particle jet impact increases with the increase of jet velocity and particle mixing ratio in high-pressure water-jet, and decreases with the increase of particle diameter. According to the requirements of particle jet impact drilling technology and the analysis findings, it is recommended to adopt water-jet velocity of 200-220 m/s, particle mixing ratio in water-jet of 0.20%, and particle diameter of 1.0 mm. Research results can provide theoretical basis for the parameters optimization and field application of particle jet impact drilling technology.