Study of the Critical Speed of Ultra-High-Speed Diamond Drilling Technology in Marble

In order to effectively improve the drilling speed in deep hard rock and save drilling costs, this study explores the transformation mechanism and critical velocity range of ultra-high-speed diamond drilling technology on rock breaking effect, using marble as an example. The study establishes an ultra-high-speed single diamond fragmentation model using the finite element method (FEM) and solves for the unknown critical velocity of marble in this drilling technique. Additionally, small diameter bit drilling experiments were conducted on our self-developed ultra-high-speed diamond drilling test bench. Based on existing simulation results and experimental studies, we discuss the critical velocity problem and compare and analyze the change in the rock-breaking mechanism and mechanical specific energy (MSE) under conventional drilling versus ultra-high-speed rotary drilling conditions. Our results indicate that changes in rock breaking mechanisms under ultra-high-speed diamond drilling conditions are limited to a specific speed range and do not persist with increasing speeds. Furthermore, experimental verification confirms that ultra-high-speed diamond drilling can effectively reduce MSE and increase the rate of penetration (ROP) by altering the rock-breaking mode. It is hoped that these findings will provide valuable insights for applying this technology to various hard rocks.