Lessons on internal erosion in embankment dams from failures and physical models (Keynote)

The investigations of embankment failures reported by Erinoh R&D project, merged with the Foster & Fell Erdata and NPDP program in the USA, point out the main causes and the main situations where internal erosion could initiate and trigger the failure of dams. The investigation of physical models built in the CACOH laboratory of CNR shows under particular circumstances (piping at core base) pervious shells cannot provide enough weight or erosion resistance to resist concentrated leaks. Three different mechanisms of failure may occur: (1) general instability without hydraulic fracturing, (2) hydraulic fracturing (with or without suffusion) followed by piping, (3) backward erosion or sloughing (surface instability). Physical models help to understand the conditions and the physical situations in which each of these three modes of failure apply. This paper relates to these physical tests and presents the main results and conclusions.