Influence of particle-size distribution on shear characteristics of slip zone soil and its mesoscopic mechanism

In order to explore the effect of particle-size distribution (PSD) on the shear characteristics and deformation characteristics of slip zone soil, 13 sets of medium-sized shear tests were designed by using the mixture test design method. The mathematical expressions of the fractal dimension D and traditional PSD parameter Cu were deduced, and a mixture model was established to predict the internal friction angle of soils with different PSD. Two tests were then used to verify the correctness of the model. The visualized shear box facilitates the recording of soil deformation characteristics during shear. Interval photography was used to record the deformation information of the soil during shear, which was extracted by using Particle Image Velocimetry technology and displayed using Tecplot software. These features were examined and considered for connections with D. The results show that the mixture test can be used as a means to study PSD, and D can describe the change of PSD and link the macroscopic strength of the soil with the mesoscopic properties. Understanding the mechanical properties of soils under different PSD and explaining them at the mesoscopic level can help to better understand the mechanism of landslides and can also provide a basis for the selection of PSD for subgrade soil.