Coupled Chemical and Mechanical Damage Model for Acid-Corroded Sandstone

Abstract

Taking the sandstone subjected to pH = 1 and 3 HCl solutions as the research object, a dynamic chemical damage model was established based on mineral dissolution theory and chemical kinetics principles. A mechanical damage model of sandstone was also established by continuous damage mechanics theory. Moreover, a coupled chemical and mechanical damage model was deduced through microstress analysis, and a damage constitutive model for acid-corroded sandstone was constructed based on the Weibull distribution and the D–P criterion. The results showed that the acid–rock reaction showed evident time dependence, and the reaction rate decreased with the prolongation of corrosion time. The chemical damage variables of corroded sandstone subjected to pH = 1 and 3 HCl solutions reached 0.34 and 0.12 after 180 days, respectively. The damages caused by chemical and mechanical actions are nonlinear with the generalized damage. The chemical action can slow down the deterioration rate of sandstone under load, which was more obvious as the immersion time extended and the pH values of the solution declined. The stress state could change the deterioration process of sandstone, and the damage rate declined as the confining pressure increased. Finally, the uniaxial and triaxial compression test results verified the theoretical model, and the two agreed well, which verified that the coupled damage model is reasonable and applicable.