An Improved Local Coarsening Method for Discrete Element Simulation on Cracking Propagation in Rock and Rock-Like Materials

Abstract

One key aspect of optimizing numerical techniques is balancing accuracy with computational cost. However, the traditional local coarsening method (LCM) used in the discrete element method (DEM) always overlooks size-dependent characteristics, which can lead to inaccuracies compared to other numerical methods. This study quantitatively analyzed the errors in macroscopic mechanical properties and deviation in cracking behavior resulting from this oversight. The results indicate that mechanical property errors can even reach up to around 20% ~ 30%, with cracks tending to propagate into local coarsening regions. Further investigation revealed that these unrealistic phenomena are primarily due to reduced contact stiffness resulting from enlarged particle size. To address this issue, an improved local coarsening method (ILCM) for DEM was proposed, focusing on minimizing the stiffness difference between fine and coarse regions. The effectiveness of the proposed ILCM was validated through a series of Brazilian numerical tests on both intact samples and samples with prefabricated fractures.

Keywords: local coarsening method, discrete element method, deviation mechanism, stiffness in-consistency, crack propagation