Evaluation of the constriction size reduction of granular filters due to upstream cohesive base-soil erosion

Abstract

This study is devoted to filter-constrictions analysis and its application with respect to void and constrictions reduction during soil filtration. The experimental investigation involves combined Hole Erosion-Filtration tests using several soils and filters. The base soils are lean clays and the granular filters are selected according to the usual filtration criteria. The combination of the experimental data for porosity variation and the analytical results from the Constriction Size Distribution (CSD) analysis was used to evaluate the constrictions size reduction subsequent to the filtration process. The filtration depth was also estimated according to the retained soil mass and the porosity reduction deduced from the measured hydraulic conductivity. An analytical model of the CSD was applied to the experimental results in order to assess the constrictions reduction. As regards the obtained results, a non-uniform constriction reduction was suggested according to the effective filtration depth, advocating a dynamic filter action.