Ladybower Dam on the River Derwent in Derbyshire is one of the highest and steepest old puddle-core dams in the UK, with a height of just over 40m. The dam has been subject to severe settlement since its completion in 1944, with total settlements of more than 1.5m measured. Although the crest has been made up to level some six times since completion, the dam has continued to settle, resulting in an inadequate freeboard against a probable maximum flood. For this reason it was necessary to reinforce the downstream slope, raise the crest and increase freeboard to provide a margin against future loss by settlement.
Initially GCG was involved in the assessment of the ‘original’ dam and the mechanisms responsible for the on-going settlement. The results showed that the continuing settlement did not imply an inadequate factor of safety against sudden collapse. In addition to this mainly numerical work, GCG carried out a detailed assessment of the historical field settlement data and the data obtained from various site investigations.
The second stage of the analyses concentrated on the reconstructed dam predicting the settlements of the ‘new’ crest and comparing its settlement behaviour with that of the ‘original’ dam. It was also necessary to examine the overall stability of the ‘new’ section and the stability of the ‘original’ crest and its rubble wall when surcharged by the ‘new’ fill. Finally, the stability and movement of the reconstructed dam, when subjected to a flood surcharge and earthquake shaking, were considered.
Publications
Kovacevic, N., Potts, D.M., Vaughan, P.R., Charles, J.A. and Tedd, P. (1997). Assessing the safety of old embankment dams by observing and analysing movement during reservoir operation. Proc. 19th ICOLD, Florence, Italy, 551-566.
Vaughan, P.R., Chalmers, R.W. and MacKay, M. (2000). Ladybower Dam: Analysis and prediction of settlement due to long term operation. Dams 2000, Proc. 11th Biennial Conference, British Dam Society, Bath, UK, 360-376.
Kovacevic N., Vaughan, P.R. and N. Potts, D.M. (2009). Finite element analysis of Ladybower Dam: long-term operation and dam raising. Proc. 2nd Int. Conf. Long term behaviour of dams, Graz, Austria, 808-813.
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