Toe as Critical Location for Failure Initiation in Rockfill Embankments

Numerous descriptions of past instances of large rockfill dam failures under overtopping conditions have suggested the toe section as a critical location for initiation of unravelling embankment failure. However, corroborative experimental evidence in support of these observations is currently not available in international literature. This article essentially aims at addressing this issue by investigating the stability aspects of test rockfill embankments under incremental overtopping conditions. Observations from experimental investigations conducted on 0.6 m and 1.2 m high model rockfill embankment dams with downstream slope of 1V:1.5H have been further analysed with an objective of better understanding the behaviour or rockfill embankments exposed to overtopping flows. The study findings suggest toe as the critical location for initiation of unravelling failure of rockfill embankments in comparison with the internal dam sections. Furthermore, it is also demonstrated that removal of individual toe stones does not necessarily entail irreversible toe failure. Also, study findings are juxtaposed with available international literature pertaining to design of rockfill embankment toe.