Modified nonlinear viscoelastic-plastic rheological model and parameter identification of shear rheological model for granite

Two kinds of dry and saturated shear rheological tests are carried out on the granite in Bangpu mining area of Tibet. According to the test results, the shear rheological properties of granite are analyzed. Based on the mechamical state characteristics of granite at accelerative shear rheological stage, an improved nonlinear viscoelasto-plastic rheological model is proposed. The core of this model mainly consists of Kelvin of (conditions for judging shear stresses) and modified nonlinear Newton components of (conditions for judging strain value). This model is able to reflect the rock rheological law under shear stress loads with different levels. By using the proposed model, the nonlinear characteristics of rocks at accelerative rheological stage can be well and resonably demonstrated. Parameter identification is carried out for the shear rheological text results of the granite in Bangpu mining area of Tibet. The obtained theoretical curves of modified nonlinear viscoelastic-plastic rheological model agree with the test data. The proposed model is validated to be correct and reasonable.