ELASTOVISCO-PLASTIC RHEOLOGICAL EXPERIMENT AND NONLINEAR RHEOLOGICAL MODEL OF ROCKS

A set of creep experiments were performed to study the elastovisco-plastic characteristics of iherzolite specimens in mining area III of Jinchuan Group Ltd.by the circular increment step load and unload method and single-stage loading method.Based on scientific analysis of experimental data,the nonlinear elastovisco-plastic deformation characteristics of this kind of rock were studied in detail.With the attenuation creep being divided into viscoelastic and viscoplastic portions,their nonlinear regression fitting functions were brought forward respectively.The fitting functions of steady creep rate and accelerative creep rate were built,in which stress σ and time t were viewed as independent variables.According to loading and unloading creep test curves under different stress levels,by connecting the instantaneous elasticity Hooke body,viscoelasto-plastic Schiffman body and viscoplastic improved Bingham body in series,a new nonlinear elastovisco-plastic rheological model of rock was proposed.The method to confirm nonlinear parameters of components was proposed.The rheological model with two yield limitations were brought forward and the parameters of the components were nonlinear functions in which stress σ and time t were viewed as independent variables.So rheological model can reflect the rheological rules of rocks under different stress levels,especially it can simulate the accelerative creep.3D creep and rheological equations under constant stress were deduced.On the basis of complete creep curves gained by RYL–600 rock servo-controlled rheology equipment,the identification of the proposed nonlinear elastovisco-plastic rheological model of rock is validated.The comparison between nonlinear rheological model and experimental curves show that two curves accord well each other,and the proposed nonlinear elastovisco-plastic rheological model is available and reasonable.