Experimental Investigation on Anisotropic Creep Characteristics of Quartz Mica Schist

To investigate the anisotropic rheological properties of quartz mica schist in the underground chamber of Danba hydropower station, two groups of uniaxial compression creep tests were conducted on quartz mica schist samples. Based on the creep characteristics of quartz mica schist, the damage Nishihara model was improved by adding a nonlinear viscous component in series, the creep equation was derived in the light of the Lemaitre strain equivalence principle, and one-dimensional rheological mechanical parameters were obtained. Furthermore, the effects of schistosity and stress level on transient creep, decelerating creep, steady-state creep, accelerating creep and other creep characteristics were analyzed. The research results show that with the increase of stress, the instantaneous elastic modulus of quartz mica schist remains a constant roughly, but its hysteretic elastic modulus, stable viscous coefficient and creep failure time decrease. Quartz mica schist exhibits a strong visco-plasticity and high strength when loading direction is perpendicular to schistosity, while quartz mica schist shows strong instantaneous elasticity, visco-elasticity, viscosity and ductility when the loading direction is parallel to schistosity.