Statistical study of no-erosion filter (NEF) test results

Filter design criteria predicated on no-erosion filter (NEF) test results are widely adopted for filter substantiation in earth dams. Hitherto, repetitions of NEF tests on various base-soil–filter combinations have suggested some anomalies between test results and accepted filter criteria. This treatment analyses a large database of NEF tests available in the literature, and carefully assesses the influences of different base-soil properties, including d₈₅, fines content, clay content, plasticity index and sand content on the experimentally defined boundary filter (i.e. D_15b). The parametric study presented, alongside the available criteria, may improve the design of optimum—that is, safe and economical—filters.