The Sheffield Dam was 7.6m high dam constructed in 1917. The body of the dam was composed of silty sand and sandy silt, the upstream slope was faced with a 1.2m thick clay blanket protected by a 12.5cm concrete facing and extended 3m into the foundation to serve as a cut-off. Compaction was done by routing construction equipment over the fill. The foundation consists of a layer of terrace alluvium 1.2 to 3m thick overlying sandstone bedrock.
The earthquake main shock occurred at 6:42 am on 29 June, 1925. The magnitude of the earthquake was assessed at 6.3 with the epicenter located about 12kn N.W. of the dam site and maximum ground acceleration of 0.15g of the site. Though there were no eye witnesses to the failure, subsequent inspection reports indicated that sliding occurred near the base of the embankment, causing a section about 90m in length to move bodily downstream as much as 30m, breaking up as it did so. There can be little doubt that a movement of this extent was related to liquefaction induced by shaking.
Resource: Bharat Singh and R.S. Varshney, Engineering for Embankment Dams, 1995, A.A.Balkema
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