Numerical simulation of the influence of seepage direction on suffusion in granular soils

To study the internal phenomenon of suffusion process in granular soils and determine its influence of the seepage direction, numerical simulations were conducted using the Particle Flow Code (PFC) software in different seepage directions. The fixed coarse-grid fluid scheme in PFC^3D was used for particle-fluid coupling simulations, and a new gravity-applied method was implemented to simulate different seepage directions. Variations in the mean contact force, flow rate, porosity, permeability, and number and volume of escaped particles with an increasing hydraulic gradient and the migration pathways of fine particles during the simulation were monitored and analyzed. The results show that a larger seepage angle corresponds to a smaller flow rate under the same hydraulic gradient. The fine particles initially moved downward under gravity and then stopped and remained at a certain position. The fine particles subsequently began to move upward and finally escaped from the top surface of the model. The migration pathways of fine particles were random and their directions of motion changed continuously.