Determination of tension-softening curve and fracture behavior evaluation in granite with crack tip toughness

The tension-softening model has been employed to evaluate the crack growth behavior in rocks. In this paper, the tension-softening relation was determined taking the crack tip toughness into account. The extended J-based technique is applied to determine the tension-softening curve for a granite which has crack tip toughness. Compact tension (CT) specimens were used to conduct J-based fracture toughness tests on the granite. The crack tip toughness was measured using K-resistance curves in the granite. Three sizes of CT specimen were used to examine the specimen size effect on the deduced tension-softening curves. It was shown that the extended J-based technique provides reasonable tension-softening curves irrespective of the specimen size, suggesting the validity of the extended J-based technique. Finally, the necessity of the introduction of the crack tip toughness is demonstrated by performing numerical simulations of the load-displacement behaviors of the granite.