Study of nonlinear shear creep model and creep property experiment of water-rich soft rock

Water-rich soft rock roadway with fast deformation speed,large deformation and support difficulty,the key for this issue is to establish a rheological model describing the characteristics. Through shear creep test of soft rock with different moisture content,the experimental results show that under the same shear stress level the instantaneous elastic modulus,the ultimate deformation modulus and the coefficient of viscosity of soft rock decreases,the creep rate increases first and then decreases,the destruction time of accelerated creep is shortened with the increase of moisture content;With the increase of shear stress,the instantaneous shear displacement,creep deformation and the radius of curvature of the attenuation creep stage increase gradually under the same moisture content. According to the nonlinear characteristics of water-rich soft rock creep,a nonlinear shear rheological model is established to describe the creep characteristics of water-rich soft rock,and model parameters are identificated based on the BFGS algorithm and univer- sal global optimization method,the identification results agree well with the experimental curves,which show that the model is correct and reasonable. It is very important significance for rich-water soft rock roadway stability research in the deep and complex geological mechanics environment.