Applicability of Filter Design Criteria for Wet Core Embankment Dams in Wet Climates

Abstract

Abstract In humid and rainy climates, many embankment dams are constructed with core materials, possessing moisture in excess of optimum compaction water content. Since internal erosion and piping are major culprits of embankment dam failures, it would be practically important to understand whether contemporary filter design criteria, which make no reference to moisture content or compaction ratio of soils, are applicable to wet-under compacted cores. In this treatment, 123 no erosion filter (NEF) tests were performed on eleven core materials with varying moisture contents and compaction ratios. Results suggest that proper filter functionality depends on moisture in excess of optimum, soil Plasticity Index, and D15/d85. With increase in excess moisture, a smaller D15/d85 is required for erosion prevention, insomuch as filters designed via recommended criteria, may become inadequate, when the core is excessively wet and under compacted. Generally speaking, D15/d85 ≤ 9 is reliable for cores with limited excess water content and compaction ratios over 95 %; whereas D15/d85 ≤ 7 should be applied for compactions above 90 % and moistures significantly beyond optimum.