EXPERIMENTAL AND NUMERICAL SIMULATION OF THE MICROCRACK COALESCENCE MECHANISM IN ROCK-LIKE MATERIALS

Rocks and rock-like materials frequently fail under compression due to the initiation, propagation and coalescence of the pre-existing microcracks. The mechanism of microcrack coalescence process in rock-like materials is experimentally and numerically investigated. The experimental study involves some uniaxial compression tests on rock-like specimens specially prepared from portland pozzolana cement, mica sheets and water. The microcrack coalescence is studied by scanning electron microscopy on some of the prepared thin specimens. It is assumed that the mica sheets play the role of microcracks within the specimens. Some analytical and numerical studies are also carried out to simulate the experimentally observed microcrack coalescence phenomena within the specimens. A higher-order indirect boundary element method known as higher-order displacement discontinuity method implementing special crack tip elements to treat the singularities of stress and displacement fields near the crack ends is used to estimate the Mode I and Mode II stress intensity factors at the microcrack tips. The maximum tangential stress fracture criterion is implemented in a sophisticated computer code using the linear elastic fracture mechanics theory and the propagation and coalescence of random microcracks within the rock-like specimens are numerically simulated based on an iterative algorithm. The proposed analyses are validated by comparing the corresponding experimental and numerical results of microcrack coalescence phenomena of rock-like materials.