Creep behavior of layered salt rock under triaxial loading and unloading cycles

This paper presents an extensive laboratory investigation of layered salt rocks under triaxial loading and unloading cycles aiming to better understand their viscoelastic plasticity strain characteristics. Specifically, creep curves were obtained from the triaxial loading and unloading tests and analyzed using the Burgers model. The microstructure of the layered salt rocks before and after the creep test was comparatively analyzed using the dry grinding optical diagram. The results show that the creep deformation of layered salt rocks is mainly viscoelastic under a low deviatoric stress and contains both viscoelastic and viscoplastic deformations when the deviatoric stress is high. With the increase of deviatoric stress, both the instantaneous elastic and plastic strains increase, and the increasing rate becomes lower as the deviatoric stress increases. The creep curves of layered salt rocks can be well represented with the Burgers model. Since the creep leads to fracturing and interlayer rupturing and producing new fluid seepage channels in layered salt rocks, this study has great value for understanding the long-term performance of gas and hydrocarbon liquid storage caverns in layered salt rock formation.