Constitutive model and mechanical properties of fractured rock mass under triaxial compression

As is known, evaluating strength degradation characteristics of rock mass of great importance in civil engineering. This research is conducted to assess the influence law of disrupt characteristics and confining pressure on the mechanical characteristics of rock mass. The results show that the strength of rock samples linearly increases with the increase of confining pressure. The strength reduction rate of rock samples decreases more obviously with the increase of fracture length and quantity, and the strength effect is most obvious when the confining pressure increases. With the increase of confining pressure, the failure mode of intact rock samples changes from tension to shear, the rock samples with different lengths/quantities of prefabricated fractures all undergo shear failure, but as the quantity of fractures increases the rock samples ultimately exhibit a "rhombus" failure mode. On this basis, a damage constitutive model was established that can reflect the characteristics of the entire deformation and failure process of fractured rock masses. The model parameters m and F0 can reflect the brittle and strength characteristics of the rock mass. The stress-strain curve and damage evolution curve of the rock mass have a good correspondence with the macroscopic failure process induced by its structural changes. The macroscopic defects formed by prefabricated fractures have a significant impact on the initial damage state of the rock mass, leading to a deterioration of its mechanical properties. All in all, the research results provide important theoretical basis for the prevention and safety evaluation of similar fractured rock engineering disasters.