ROCK · FRACTURE VIA STRAIN-SOFTENING FINITE ELEMENTS

AssnlACT: The fracture of rock is assumed to arise from propagation of a blunt crack band with continuously distributed (smeared) microcracks or continuous cracks. This approach, justified by material heterogeneity, is convenient for fi-nite element analysis, and allows analyzing fracture on the basis of triaxial stress-strain relations which cover the strain-softening behavior. A simple compliance formulation is derived for this purpose. The practical form of the theory in-volves two independent material parameters, the fracture energy and the ten-sile strength. The width of the crack band front is considered as a fixed material property and can be taken as roughly five-times the grain size of rock. The theory is shown to be capable of satisfactorily representing the test data avail-able in the literature. In particular, good fits are demonstrated for the measured maximum loads, as well as for the measured resistance curves (R-curves). Sta-tistical analysis of the deviations from the test data is also presented