Optimization Research on the Drilling Parameters of the RC-DTH Air Hammer by Employing Smoothed Particle Hydrodynamics

Down the hole (DTH) air hammer is widely used in hard rock drilling for its high drill rate. Revealing the influence mechanism of drilling parameters by RC-DTH air hammer is of great significance to promote the application of RC-DTH air hammer impact rotary rock breaking technology in deep hard rock drilling. In this paper, based on LS-DYNA and Smoothed Particle Hydrodynamics, a three-dimensional numerical simulation model of piston-bit-rock in the RC-DTH air hammer impact rotary drilling is established to explore the propagation and action law of stress wave in rock and drilling tools, and to analyze the influence of different drilling parameters on the rock fragmentation effect. A testing facility, known as the RC-DTH air hammer impact energy test platform, has been constructed to confirm the accuracy of the numerical simulation results obtained. After a thorough analysis that accounts for the effects of stress concentration and drilling parameters on the efficiency of rock breaking, the identified optimal operating parameters are as follows: a drilling pressure of 4000 Newtons, a piston impact velocity ranging from 9 to 11 m per second, and a drill bit rotation speed of 30 rpm. Field tests confirmed that applying this optimal parameter set increased the single-impact energy of the hammer by approximately 32.5%, and optimized the energy transfer efficiency to around 17.5%, thereby achieving a quantifiable engineering balance between improving rock-breaking efficiency and reducing tool wear.