A hybrid discrete element method with adaptive contact treatment approach for modeling discontinuous rock masses

Abstract

The Discrete Element Method (DEM) has been widely used to simulate the mechanical behavior of discontinuous rock masses, particularly in underground environments; however, its applicability is often limited to specific contact conditions, such as quasi-static or dynamic interactions. To achieve broad applicability, this study presents a Hybrid Discrete Element Method (hDEM) that adaptively selects between different numerical schemes for contact treatment. The proposed method employs a threshold velocity based on the principle of energy conservation to distinguish between computational schemes at contact: a force-based method is applied to quasistatic contacts, while an impulse-based method is used for dynamic contacts. This approach enables hDEM to accommodate varying contact conditions within a unified framework. Several metrics, validated against theoretical solutions, demonstrate that the proposed approach yields accurate and stable results across different loading scenarios, addressing some of the limitations observed in conventional methods. The relative error of contact force was controlled within 5x10-4 % in static tests and the mean absolute error of the velocity was recorded as 3.41x10-3 m/s in dynamic tests. In a comparative simulation of tunnel excavation, hDEM achieved results similar to conventional DEM while reducing the number of convergence cycles by 65.4%, highlighting its efficiency and potential as a practical numerical tool for adaptive contact treatment of discontinuous rock masses.