A configurational-force-guided intra-element cracking strategy for ECZM-FDEM rock fracture simulation

Abstract

Crack paths in cohesive-zone-model-based finite-discrete element method (CZM-FDEM) simulations are often constrained by pre-existing element boundaries, while intrinsic cohesive insertion may introduce artificial compliance before fracture activation. This study develops a configurational-force-guided intra-element crack-insertion strategy within a master–slave node-binding ECZM-FDEM framework for rock fracture simulation. After the local cohesive activation criterion is met, a composite configurational force recovered from neighbouring solid elements selects candidate intra-element insertion directions. Accepted insertions are then incorporated through a local topology update: affected CST/T3 parent elements are subdivided, active and dormant cohesive interfaces are introduced, nodal variables are transferred using a generalized s -split rule for non-midpoint edge intersections, and new active interfaces are initialized before the topology change is committed at the end of the current explicit step. Brazilian splitting, uniaxial compression, and flaw-containing compression simulations show that the strategy provides additional local crack-path freedom on coarse meshes while preserving the pre-activation continuum response. The results also quantify the effects of topology transfer, mesh resolution, and computational cost, providing a practical basis for intra-element fracture modelling in ECZM-FDEM.