Determination of dynamic fracture properties of rock materials using a modified compact test method

Fragmentation produced by explosive blasting and impact penetration of rock depends largely in the dynamic fracture process involving the nucleation and propagation of microcracks that finally coalesce, breaking the rock into fragments. Moreover, rock is an inhomogeneous material, which follows a stochastic process in fracturing. This causes the nonlinear behavior and strain rate dependency of the fracture properties under a dynamic load. In this study, a modified compact test (MCT) was suggested to investigate the fracture process zone near the crack tip and fracture toughness of rock materials. By adopting the FEM analysis, the geometry design of MCT was determined. Furthermore, the stress intensity factor for MCT method with consideration of specimen geometry was also determined in this study. A dynamic measurement system was adapted to observe the dynamic fracture process zone around the running cracks. Fracture toughness obtained by J-integral-based technique were compared with the fracture toughness determined by the suggested stress intensity factor in this study.