Quantitative calculation of the damage of carbonaceous mudstone during uniaxial compressive failure process under dry–wet cycling

This paper presents a theoretical analysis of the damage evolution law of carbonaceous mudstone during compressive failure process under dry–wet cycling. In this study, microscopic testing and uniaxial compression synchronous acoustic emission testing systems are employed to examine the microstructure, mechanical properties, and failure acoustic signal of carbonaceous mudstone. The results demonstrated that dry–wet cycling aggravated the mesostructure damage of carbonaceous mudstone. As the dry–wet cycling increased, the pores of carbonaceous mudstone increased, and the disorganization of the mesostructure became more serious, leading to reductions in peak stress, elastic modulus, and cumulative acoustic emission signals. The analysis of PFC (Partical Flow Code) revealed that the number of crack propagation in carbonaceous mudstone increased, and the crack morphology became more complex under dry–wet cycling. A comprehensive framework was developed to incorporate crack propagation into the damage process, where in the growth of cracks exhibits an "S-shaped" pattern with axial strain. As the number of dry–wet cycling increased, the threshold strain for the accelerated damage increased, and the crack growth rate decreased, along with a decrease in the initiation damage stress. This damage pattern was further evidenced by the identification of the crack propagation morphology and rock failure localization during dry–wet cycling. The proposed method showed good consistency with the experimental test results and numerical simulations, enabling quantitative calculation of compression-induced damage in carbonaceous mudstone.