Experimental and Theoretical Study on the Creep Behavior of a Clayey Rock

An understanding of the creep behavior of clayey rocks is considered fundamental for further development in the fields of nuclear waste underground disposal, underground mine design, strata control, and many other geological phenomena occurring in the earth’s crust. In this research, we performed a series of long-term triaxial compressive tests on a typical clayey rock, which confirmed its high creep potential beyond the creep threshold. Further analysis of the creep mechanism of this clayey rock indicated that two effects—strengthening and damage—are accompanied by the creep process. Additionally, based on the overstress theory and Drucker–Prager cap model, we developed a novel constitutive model considering two creep reference surfaces—cohesion and consolidation. Meanwhile, laws to reflect the strength and damage effect during creep were established and applied to the above constitutive model. Finally, the above theoretical studies were implemented in the finite element method software ABAQUS FEA using the subroutines CREEP and USDFLD. Some theory parameters were verified through back analysis. A comparison between the experimental results and numerical simulations confirmed the superiority of the established theoretical model.