Volume 27, Issue 1 (January 2004)
Self-Healing of Concentrated Leaks at Core-Filter Interfaces in Earth Dams
Concentrated leaks at core-filter interfaces in earth dams increase erodibility of soils, which may lead to catastrophic failures. In this paper, mathematical and experimental testing methods are suggested to determine the self-healing nature of these leaks. The methods are fundamentally different from the existing empirical methods in that they do not involve comparison of particle sizes of the base (D85) and filter (D15) soils. They are based on the fundamental processes of particle transport and deposition phenomena. An advection type equation is used with a deposition coefficient (λ) to describe particle transport in filters. The nature of particle deposition at the interface, which is described by an exponential attenuation function with respect to distance, is used to infer the possibility of self-healing. The experimental method involves extension of a test previously published in this journal. The method essentially involves a flow pump to evaluate the erodibility of base soils, determine λ and characterize the filters, and test combined base soil-filter systems to evaluate self-healing potential of a number of filters relative to each other. The results from the experimental method using three different filters and a Group II base soil were interpreted and analyzed using the mathematical model. The methods suggest that the entire particle-size distribution, and not mere D15, governs particle accumulation at the interface. The proposed methods are useful for relative comparison of self-healing capabilities of various filters for a given base soil.