CFD-DEM modeling of filtration through conventional and conical geotextile filter systems

A significant contributor to retaining wall structural failure occurs due to inadequate drainage in the backfill. A numerical model based on a computational fluid dynamics and discrete element method (CFD-DEM) coupled approach was developed to simulate particle movement in the graded filter zone and piping through the geotextiles. The model was used for conventional as well conical geotextile filter systems that use a series of woven geotextiles filtering a coarse-grained backfill soil. The model results were compared with laboratory results to verify the accuracy. The results indicated that conical filter systems contribute to higher soil piping rates but provide higher permeability than conventional geotextile filtration system counterparts. The model predictions compared with the laboratory measurements indicated that the movement of particles (i.e. suffusion) influenced the soil-geotextile contact zone permeabilities and caused a decrease in system permeabilities. A retention ratio, αsl, successfully predicted piping rates for different types of woven geotextiles with a percent error range of 13-29%. Overall, the model predictions matched the laboratory results within an order of magnitude or less, indicating the predictive capability of the model.