Effect of Particle Size on Mechanical Properties of Coarse-grained Soil

In order to explore the effcet of particle size on the mechanical properties of coarse-grained soil, 40 groups of direct shear tests were conducted on 3 kinds of coarse-grained soil with the same dry density by DHJ50-2 shear test machine. The results show that the cohesive forces decreases with the increase of particle size, and the internal friction angle increases with the increase of particle size. Under low density and low vertical load, the peak shear stress of coarse-grained soil decreases with the increase of particle size. The threshold porosity of 3 kinds of coarse-grained soil was calculated. When the porosity of soil sample is lower than the corresponding threshold porosity, the peak shear stress increases with the increase of particle size. The research results have certain significance for the follow-up study of mechanical properties of complex graded soil.