Study on Creep Damage Model of Yellow Sandstone with Step Loading and Unloading under the Action of Wetting-drying Cycles

Abstract

Abstract This study performs uniaxial compression and step loading and unloading creep tests on rock samples under different wetting-drying cycles with yellow sandstone to investigate the creep characteristics of rock bodies after excavation or excavations with step loading and unloading under external forces. Moreover, it constructs a creep damage model based on the nonlinear rheological theory and damage mechanics to describe the instantaneous elastic strain, instantaneous plastic strain, nonlinear viscoelastic strain, and nonlinear viscoplastic strain of rocks. Besides, it proposes a creep model parameter identification method based on the creep curve characteristics. The results have shown that the action of wetting-drying cycles causes a weakened decrease in elastic modulus, uniaxial compressive strength, and long-term compressive strength of yellow sandstone, in line with the exponential function change relationship. The specimen damage type evolves from shear damage of a single oblique section to conical shear damage of a double oblique section. Additionally, the creep rate is not constant in the steady-state creep stage but constantly changes with time, and the fluctuation range increases with the increase in the wetting-drying cycles. The creep damage model parameters Eme, Emp, Eve, and ηve do not differ much under the same stress condition, and each parameter is influenced by the creep stress σ at a specific law. The Eme, Emp, and σ have a linear relationship, whereas the Eve, ηve, and σ have an exponential one.