A damage mechanical constitutive model of unloading failure for brittle-elastic rock mass

Based on damage mechanical theory and giving some assumptions of rock mass, a damage constitutive model of unloading failure for brittle-elastic rock mass is proposed in the paper. In the model proposed herein, the behavior of rock mass is decomposed in two parts. The first part represents topical (continuum) behavior, which obeys elastic constitutive law. The second part refers to damaged or fractured part, the behavior is such that its stiffness is assumed to be zero. The form of the model is simple and its physical meaning is clear. For verifying the model, a series of true triaxial tests of red sandstone specimens were performed. The red sandstone specimens came from the Emei Mountains in Sichuan, China. The tests adopted four experimental types that correspond to four excavation ways and obtained the stress-strain curves in each type test. By means of comparison of experimental results, it is shown that the model is very good agreement with tests. Thus, the model could be applied to unloading failure of brittle-elastic rock mass.