Numerical analysis based on the non-linear dynamics method (AUTODYN) is performed to simulate the cracking processes in rocks containing a single pre-existing flaw. The dynamic analysis considers the interaction of the material with the stress wave, which propagates from the pressure boundary towards the model interior. The numerical results presented are based on the Drucker-Prager strength model along with the cumulative damage failure criterion.
The resultant crack types, crack initiation sequences and overall crack pattern are found to vary with loading conditions. Under a relatively low loading rate or a small magnitude of maximum loading pressure, tensile cracks tend to initiate prior to shear cracks. In contrast, under a relatively high loading rate and a large magnitude of maximum loading pressure, shear cracks tend to initiate prior to tensile cracks instead. Besides the loading rate, the maximum magnitude of the loading pressure is also found to influence the crack pattern. When the magnitude of maximum loading pressure is small enough, even if the loading rate is very high, the tensile cracks will initiate first and even no shear crack will initiate. To conclude, the crack pattern caused by quasi-static load can be expected to be very different from the that caused by high speed impact load.