Analyzing Discrete Rock Crack Growth and Interaction

ABSTRACT: This paper presents the salient features of a unique rock fracture mechanics model for analyzing failure loads based on the underlying microstructure of the rock type. DIGS (Discontinuity Interaction and Growth Simulation) uses the displacement discontinuity boundary element method with an efficient iterative solver to predict the initiation, growth, and coalescence of multiple fractures within a rock under multi-axis loading. 2-D demonstrations are presented for coupon triaxial compression and laboratory borehole stability tests. The model captures many aspects of rock failure including the overall strengthening as confinement pressures increases, brittle failure and axial splitting in uniaxial compression, shear failures that occur with the application of slight confining loads, and the transition from brittle to ductile behavior with increasing confinement. DIGS provides an unambiguous prediction of the large-scale fracture paths leading to the failure and is shown to delineate rock behavior based on grain scale properties.