The deep rocks generally present high strength, plasticity and abrasiveness, which greatly limit the efficient drilling of the bit. Particle impact drilling (PID) technology is a new and efficient drilling method, but its rock-breaking mechanism is still unclear. In present study, a numerical model which truly reflects the mineral composition and granule diameter distribution of granite is established based on the particle flow code (PFC) to optimize the particle impact parameters. The law and mechanism of rock breaking by single particle impact, multi-particle impact and auxiliary cutting with different particle diameter, incident angle and incident velocity are studied. The results showed that the crack number and broken volume fluctuate with the change of incident parameters. Microcracks mostly occur in the longitudinal direction of rock. During particle impact, the formation, expansion and coalescence of microcracks are all along the mineral crystal, while the situation is just the opposite in cutting. With particle impact assisted, the cutter can easily penetrate into the rock and the rock presents brittle failure. This research also includes experiments to examine the generation of cracks and chips. To improve the efficiency of auxiliary rock breaking, it is recommended to use particles with a diameter of 3.0 mm and an incident angle of 0°–30°, while increasing the impact velocity. This study deepens the understanding of the mechanism of rock breaking assisted by particle impact, and provides the basis for designing drilling parameters using the PID technology.

深部岩石普遍具有较高的强度、塑性和磨蚀性，极大地限制了钻头的有效钻进。粒子冲击钻井（PID）技术是一种新型高效的钻井方法，但其破岩机理尚不清楚。本研究基于粒子流代码（PFC）建立了一个真实反映花岗岩矿物成分和颗粒直径分布的数值模型，以优化粒子冲击参数。研究了不同粒径、入射角和入射速度下单粒子冲击、多粒子冲击和辅助切割的破岩规律和机理。结果表明，裂纹数量和破碎体积随入射参数的变化而波动。微裂纹多发生在岩石的纵向上。在粒子撞击过程中，微裂纹的形成、扩展和聚结都是沿着矿物晶体进行的，而在切割过程中则正好相反。在粒子冲击辅助下，刀具很容易穿透岩石，岩石呈现脆性破坏。这项研究还包括检查裂缝和碎屑产生的实验。为提高辅助破岩效率，建议使用直径为3.0 mm、入射角为0°~30°的颗粒，同时提高冲击速度。本研究加深了对颗粒冲击辅助破岩机理的认识，为利用PID技术设计钻井参数提供了依据。而切割的情况正好相反。在粒子冲击辅助下，刀具很容易穿透岩石，岩石呈现脆性破坏。这项研究还包括检查裂缝和碎屑产生的实验。为提高辅助破岩效率，建议使用直径为3.0 mm、入射角为0°~30°的颗粒，同时提高冲击速度。本研究加深了对颗粒冲击辅助破岩机理的认识，为利用PID技术设计钻井参数提供了依据。而切割的情况正好相反。在粒子冲击辅助下，刀具很容易穿透岩石，岩石呈现脆性破坏。这项研究还包括检查裂缝和碎屑产生的实验。为提高辅助破岩效率，建议使用直径为3.0 mm、入射角为0°~30°的颗粒，同时提高冲击速度。本研究加深了对颗粒冲击辅助破岩机理的认识，为利用PID技术设计钻井参数提供了依据。这项研究还包括检查裂缝和碎屑产生的实验。为提高辅助破岩效率，建议使用直径为3.0 mm、入射角为0°~30°的颗粒，同时提高冲击速度。本研究加深了对颗粒冲击辅助破岩机理的认识，为利用PID技术设计钻井参数提供了依据。这项研究还包括检查裂缝和碎屑产生的实验。为提高辅助破岩效率，建议使用直径为3.0 mm、入射角为0°~30°的颗粒，同时提高冲击速度。本研究加深了对颗粒冲击辅助破岩机理的认识，为利用PID技术设计钻井参数提供了依据。