Core discing characteristics and mitigation approach by a novel developed drill bit in deep rocks

Core discing often occurs in deep rocks under high-stress conditions and has been identified as an important characteristic for deep rock engineering. This paper presents the formation mechanism of core discing firstly. Then, the interaction between diamond drill bits and rock was analyzed based on numerical modeling. A novel drill bit with an inner conical crown for the mitigation of core discing was designed and verified by simulation experiments. The mitigation method was applied in the cavern B1 of CJPL-II and satisfactory results had been achieved. The percentage of core discing had been obviously decreased from 67.8% when drilling with a rectangular crown drill bit, to 26.5% when an inner conical crown drill bit had been adopted. This paper gives full insight into core discing characteristics and provides a new method for core discing mitigation; it will potentially contribute to stress measurement in deep rock engineering.