Improved nonlinear viscoelasto-plastic rheological model of rock and its correction of hardening coefficient of viscosity

Under uniaxial loading instrument,the cyclic loading and unloading creep test on the sandy shale specimens of Dongxiang Copper Mine was done.Based on the hardening-damage mechanism of creep process,the timeliness of hardening-damage effect was proposed during the analysis of creep data.And then the coefficient of viscosity(hardening coefficient of viscosity) in the decay creep stage under high stress condition was corrected.Based on the creep mechanism of damage in the stationary creep stage,the accumulation-diffusion mechanism of rock damage effect was put forward under high stress condition.Hereby,the triggering model(nonlinear creep body) of accelerated creep according to the accumulative creep deformation of damage was introduced to describe the unstable creep characters.On these bases,introduced the instantaneous plastic component,combined with the hooker body and viscoelasto-plastic body,the nonlinear rheological model of rock was established to describe the overall process of creep.The comparison between nonlinear rheological model and experimental curves show that two curves accord well each other,the correction of hardening coefficient of viscosity is necessary,and the improved nonlinear viscoelasto-plastic rheological model is available and reasonable.