Statistical Damage Constitutive Model for Anhydrite Rock under Freeze–Thaw Cycles Considering the Residual Strength and Postpeak Stress Dropping Rate

Abstract

The stability of rock engineering in cold regions is deteriorated by the day–night and seasonal freeze–thaw environments. Therefore, it is crucial to develop a damage constitutive model that can effectively describe the damage evolution and deformation characteristics of rock under freeze–thaw cycles. In this work, a series of laboratory tests were performed to acquire the physical and mechanical evolution characteristics of anhydrite rock subjected to freeze–thaw processes. Experimental results show that as the number of freeze–thaw cycles increases, the triaxial compression strength and elastic modulus of anhydrite rock decrease exponentially, but the mass variation, ductility deformation characteristics, and micropores’ area increase. A new statistical constitutive damage model for anhydrite rock under freeze–thaw cycles considering the residual strength and postpeak stress dropping rate was proposed based on the theory of continuous damage mechanics and Lemaitre’s strain-equivalent principle. The physical meaning of the model parameters m, f0, and n represent the brittleness, ductility, and postpeak stress dropping rate of rock, respectively. Compared with the reference model, the proposed model can effectively reflect the postpeak stress dropping rate and the residual strength of the stress–strain behavior for rock with a minor error. Moreover, it is proved that the proposed model is applicable for other types of rocks with similar damage mechanisms.