Numerical simulation of layered phenomena and mechanism of wide-graded soil deposits using pluviation method for centrifuge tests

Because it is similar to the process of sand deposition under natural conditions, the sand pluviation has become a common method of model preparation for foundation models in geotechnical centrifugal tests. However, the researches on the sand pluviation mainly focus on the control of the relative density, and pays little attention to the layered phenomenon of sand, especially for wide-graded soils. Aiming at the layered phenomenon of sand in the preparation process of wide-graded soils by the sand pluviation method, the physical mechanism of layered phenomenon of sand in the process of rain preparation and the influences of falling distance, moving speed and width of sand outlet on the layered phenomenon of sand are discussed by using the PFC^3D numerical simulation software. The results show that there is no layered phenomenon of coarse and fine particles in vacuum medium. In the non-vacuum medium, the coarse and fine particles have layered phenomena of sand, because the relative velocity difference occurs during the fall of the coarse and fine particles in the non-vacuum environment. The internal mechanism is that the average surface fluid resistance of the coarse and fine particles is different due to the different radii of the coarse and fine particles, resulting in the separation of particles with different particle sizes. With the increase of the density of the environment medium, the coarse and fine particles are more easily separated during the falling process, and the falling distance, moving speed and flow rate of the sand outlet have a certain influence on the layered phenomenon of sand.