Abstract: Based on the existing research on damage softening statistical constitutive model for rocks, firstly, the analytical expressions for the model parameters and confining pressure are established for specific confining pressures by discussing the relationship between the model parameters and characteristic parameters (the stress and corresponding strain at the peak point in the complete stress-strain curve). Then, by using the Mohr-Coulomb strength criterion, the relation between the peak stress and confining pressure is developed under different confining pressures. Thirdly, the formula with general significance for the peak strain in different confining pressures is deduced through investigating the correlation between the strain at the peak point and confining pressure for different rocks. Thus, a new method to determine the model parameters is presented, and a unified damage softening statistical constitutive model for rocks which is applicable to different confining pressures is then proposed. This constitutive model has fewer parameters and the method of determining its parameters is also easy. Finally, the rationality of the new method and the proposed model is verified through comparative analysis between the theoretical and experimental results.

Key words: rock, damage, strain softening, statistics, constitutive model