Non-stationary and nonlinear visco-elastic shear creep model for shale

摘要: Abstract Based on visco-elastic shear creep experimental results of shale with four various stress levels, a new non-stationary and nonlinear model is put forward. First, stationary (linear) used to identify the parameters by discrimination criterion square correlation coefficient ( R 2 ) sum least error Q ). In model, modulus G decreases but visco-coefficient η 1 increases increasing time, which has distinct time scale effect. Then constructing relation between , forward describe deformation behavior shale. The better agreement data than does fails in predicting long-term characteristics. Therefore introducing index, constructed, can predict for end, based stress, all kinds levels predicted approximately range 0.45 MPa≤ τ ≤1.45 MPa.