Abstract：The biaxial shear rheological experiment on tufflava with grades II–V is carried out with tunnel surrounding rock of Shenzhen Lianyan Highway. Through analysis of test results and model identification，the shear rheological law of surrounding rocks different grades is discussed；and the rheological models are proposed. II and III grades of surrounding rocks can be simulated reasonably with generalized Kelvin model，as grade IV with Burgers model and V with nonlinear rheology model. The failure behaviors of surrounding rock with grades II and III are brittle fracture；and the failure behaviors of grades IV and V are plastic yielded. Rheological model parameters of surrounding rocks with different grades are gotten；besides，the comparison between the shear rheology model and experimental results shows that the proposed shear rheology model is reasonable.
