Based on the laboratory triaxial test of coarse grained soil, the discrete element method (DEM) in two dimension was used to conduct the biaxial test model, and the microscopic parameters and deformation characteristics of coarse grained soil were obtained. Under the premise of better fitting of numerical and experimental results, the same parameters were set in FLAC3D which is based on finite difference method (FDM) to analyze the changes of local stress in the compression process of the sample, so as to find out the shear fracture. Comparison of the fracture zone obtained from PFC2D and FLAC3D was also made. The results show that the stress-strain curve obtained by the DEM is in good agreement with the laboratory results, and the strain softening phenomenon occurs; The experimental results show that under 300kPa confining stress, the ratio of volume increment for (dε_v)⁄(dε_a )is first positive (shear contraction) and then negative (shear dilation), and when the confining stress is greater than 300kPa, the sample is always shearing under shear contraction; Based on the same microscopic parameters, the shear fracture generated in the PFC2D model can roughly coincide with the maximum stress fracture in the FLAC3D model.

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