Micromechanical study of core barrel drilling for rotary drilling rigs based on the discrete element method

Abstract This study developed a gravel soil granular bed model using the discrete element method, elaborating on the core barrel drilling process by integrating bond-breaking and particle flow patterns. A quantitative description of the drilling process is achieved by defining bond-breaking efficiency. The results indicate that the force on particles near the drill tooth is the greatest, and this force increases with the core barrel feed rate, which enhances drilling efficiency and exacerbates wear on the drill tooth and guide bars. An increase in rotational speed raises the force on the particles in the boundary region, leading to deeper wear of the guide bar; however, the enlargement of particle voids near the drill tooth mitigates wear. Additionally, a coupled discrete element method and finite element method are developed to analyse the effects of drilling parameters on drill tooth deformation, revealing that the design of the open hole at the top of the drill can effectively reduce the maximum equivalent stress and wear depth. The conclusions drawn contribute to understanding particle mechanics, the particle bonding damage mechanism, and drilling mechanical behavior, providing a reference for optimizing drilling operations and drill design.