Abstract: The influence of gradation missing on the shear strength properties of sandy soils was investigatedthroughout the laboratory direct shear tests and discrete element simulation methods. The results of laboratory tests show that the missing of the particle gradation leads to different degrees of reduction in the shear strength of sandy soils, and the strength of soil samples without coarse particles has the maximum strength reduction. By establishing a PFC2D numerical model that matches the results of laboratory tests, it is a good complement to the inadequacy of mesoscopic parameters monitoring in laboratory tests, mainly on the force chain morphology, dilatancy characteristics and porosity evolution of soil samples after gradation deletion. The results also show that the coarse particles play a major role in the stress transfer and the local strain of the soil during the shearing process, while the filling of the fine particles helps to improve the stability of the sand force chain network.

Key words: Sandy Soils, ParticleGradation, Shear Strength, Direct Shear Test, Discrete Element Method