A Flat-Jointed Bonded-Particle Model for Rock

Bonded-particle models (BPMs) provide a synthetic material consisting of a packed assembly of rigid grains joined by deformable and breakable cement at grain-grain contacts, and whose mechanical behavior is simulated by the distinct-element method. Contact- and parallel-bonded PFC2D and PFC3D models of circular and spherical grains suffer from the limitation that if one matches the unconfined-compressive strength of a typical compact rock, then the direct-tension strength of the model will be too large. This limitation has been overcome by creation of the flat joint contact model. This contact model provides the macroscopic behavior of a finite-size, linear elastic, and either bonded or frictional interface that may sustain partial damage such that the flat-jointed material can mimic the microstructure of angular, interlocked grains. Partial interface damage with continued moment-resisting ability (to resist grain rotation) is a microstructural feature necessary to obtain the relatively large compressive- to-tensile strength ratio of most compact rocks. The ability to match this ratio is demonstrated by creating a 3D flat-jointed material for Lac du Bonnet granite that matches the elastic modulus, direct-tension strength, and compressive strengths up to 6-MPa confinement.