This paper establishes a coarse grain soil stress-strain model based on unified strength theory and disturbed state concept（DSC）and considers the influence of Lode parameter.The model can reflect the influence of intermediate principal stress（IPS）and disturbance.According to the results of a dam coarse grain soil triaxial shear test resuits to make inversion and parameter optimization of the IPS-DSC model by using the fitting method.The simulation curve and test curve are consistent.This shows that the model can better describe the stress-strain characteristics of coarse grain soil.Further study shows that the Lord parameters and the coefficient of intermediate principal stress and the parameters of disturbance have great influence on the stress-strain curve of coarse grain soil.The stress-strain curve of coarse grain soil rises to the critical value with the increase of Lord parameters and then fall with the increase of Lord parameters and the softening phenomenon abates first and then enhances;Along with the increase of intermediate principal stress coefficient

the stress-strain curve increases and the peak increases obviously and the softening phenomenon is more prominent;The stress-strain curve rises with the increase of disturbance parameters and the softening phenomenon is reduced.