The temporal and spatial evolution law of seepage parameters in the filter based on the CFD-DEM coupled flow-solid approach

The filter, composed of coarse-grained soil materials such as sand, gravel, or pebbles, effectively prevents the loss of fine particles from the upstream while maintaining permeability within the structure. It is a critical component of hydraulic structures, such as earth-rock dams and tailings dams. If silt plugging failure occurs, it can raise the phreatic line within the dam body, compromising the seepage safety of the dam slopes. Therefore, it is crucial to investigate the silt plugging characteristics of the filter. We used the CFD-DEM fluid-solid coupling method to simulate the silt plugging process in the filter, examining the influence of parameters such as the grain size of muddy water, water pressure, and the concentration of fine particles on the filter's void ratio, hydraulic conductivity, and dry density. We also investigated the spatial and temporal evolution of these properties. The results indicate that: (1) surface siltation occurs in the filter when the ratio of the filter particle diameter to the silt particle diameter (denoted as Ra ) is less than 2.2. Silt particles pass through the filter when the particle size ratio exceeds 8.8, while internal siltation occurs when the ratio falls between these two values. The numerical results obtained using the CFD-DEM fluid-solid coupling method show good agreement with both the formula discrimination method and the pore network model (PNM). (2) The particle size ratio ( Ra ) and the concentration of fine particles significantly influence the siltation process and the final stable state of the filter. A larger particle size ratio promotes the penetration of fine particles into the filter, while a smaller ratio increases the likelihood of blockages. Higher concentrations of muddy water shorten the time required for the filter to stabilize, making it more prone to blockage. The fluid pressure difference has a lesser effect on the siltation pattern of the filter. (3) As the particle size ratio approaches the threshold for internal siltation, the void ratio's changes over time and depth closely follow an exponential function. The results of this study provide a theoretical foundation and technical support for the design and construction of filters.