Abstract: Confining pressure significantly affects the crack propagation in pre-cracked rock. Particle flow simulation is a frontier approach of researching the features and mechanism of crack propagation. In this paper we present a numerical procedure for the analysis of crack propagation in rock-like materials under compressive biaxial loads. Rock specimens with intermittent single cracks were built by a bonded particle model (BPM) and biaxial compression tests under five different confinements were modeled in PFC2D (2 dimensional particle flow code). Results reveal that when the confining pressure is 0 (which means uniaxial compression), wing cracks initiate perpendicular to the pre-existing cracks and propagate towards the direction of principal stress; however, when confining pressure increases, the angle between wing cracks and pre-existing cracks gets larger, and the wing cracks get shorter and stop developing until confining pressure reaches a certain value. Also we conclude that in addition to material type, the direction of secondary crack propagation depends on the confining pressure, too. Besides, secondary cracks can be triggered by tensile stress but the further development is affected by shear stress. The increase of confining pressure poses constraints to the development of tensile cracks, but promotes shear cracks, and the width of shear plane gets larger with confinement increasing.

Key words: cracked rock, crack propagation, biaxial numerical compression test, PFC, bonded particle model