Abstract: On the premise of assuming that micro-unit strength obeys Weibull distribution, a statistical damage softening model for rock is established based on the continuum damage theories to reflect the strain softening of rock. The model contains two undetermined coefficients, one of which can be determined by the peaks of stress-strain curves, and another depends on the micro-unit strength parameters. By analyzing the influence of the micro-unit strength parameters on the model, the model parameters are determined through optimized back analysis. On this basis, reasonable strength criterion is selected according to the micro-unit strength parameters; hence the low precision of solving model parameters by traditional methods are overcome. Furthermore, the correctness and rationality of the proposed method are verified by conventional triaxial compressive test of red-bed mudstone on YSJ-01-00 rock triaxial creep testing machine.

Key words: rock mechanics, statistical damage, micro-unit strength, Weibull distribution, back analysis