A study on multiple-crack propagation of brittle rock based on mixed-mode phase field model

Aiming at the low comparative research on the difference and application scope of the two mixed-mode phase field models (which based on the decomposition of the total elastic strain energy into tensile/compressive and volumetric/deviatoric elastic strain energy, respectively), a numeric solution method of the two mixed-mode PFMs was established by the staggered solution method with self-programmed subroutines UMAT and HETVAL of ABAQUS to simulate the whole propagation process of the double-cracked rock specimens with different center distance under uni-axial tension. Research results show that with the increase of the center distance, the initiation positions, the propagation direction of the double parallel cracks (Mode I wing-crack, the direction of propagation is approximately perpendicular to the original crack surface) and the initiation direction of the secondary cracks (Mode II) are almost unchanged, while the initiation positions of the secondary cracks are changed from the two inner-tips to the two outer-tips, and the coalescence trajectories of rock bridge are also changed from two groups of crack-coalescence to one group of crack-coalescence. The two mixed-mode PFMs can effectively simulate Mode I and Mode II crack propagation. Comparatively, the PFM based on the decomposition of the total elastic strain energy into volumetric/deviatoric elastic strain energy has closer simulation results of the secondary cracks (anti-wing crack, the direction of propagation is opposite to that of the wing crack) and the coalescence trajectories of rock bridge (the wing cracks at the crack tip extend directly opposite each other) to the test results and better applicability in simulating the multi-cracks propagation of brittle rock under complex loading conditions. © 2023, Central South University Press. All rights reserved.