Effects of Grain Scale Heterogeneity on Rock Strength and the Chipping Process

Heterogeneity is an important factor controlling fracture initiation, accumulation, and propagation within polycrystalline rock. Internal spatial variability in terms of mineralogy, grain size, and anisotropy affect the yielding process. To investigate these factors, a texture-generating algorithm integrated within a numerical model was developed to create realistic rock analogs and provide user control over geological characteristics including mineral type, grain size, and anisotropic crystal shape. A mineral-specific constitutive model was created and calibrated using published values and real laboratory strength values. Brazilian tensile strength and unconfined compressive strength (UCS) model tests were developed using the finite-difference modeling software FLAC to perform parametric analysis of a series of geological characteristics. The results show that the methodology is capable of realistically reproducing damage propagation and failure behavior similar to that observed during laboratory testing. The strength results show trends similar to those found during laboratory testing. This methodology was applied to the simulation of tunnel-boring machine (TBM) cutter excavation to investigate the effect of geomechanical characteristics on the chipping process.