Instability of embankment dams due to headward erosion caused by spillway flood discharge
2012 (English)Conference paper (Refereed)
Discharge of high spillway floods can give rise to serious headward erosion in the dam toe, which endangers the downstream slope stability of an embankment dam. In conjunction with dam rehabilitations, hydraulic model tests are made to identify this type of erosion, examine its extent and provide a basis for cost-effective rebuilding design. Four dams are included, i.e. Porsi, Långbjörn, Halvfari and Höljes. Spillway channels are often surrounded by embankments of earth/rock materials grounded on bed rock. The bed rock forms the lower boundary of erosion. Concrete structures limit the erosion development. However, not all the structures will remain in place during high floods. Driven by the spillway water, flow circulations are formed in the downstream area, as is the case with Porsi, Halvfari and Höljes. The headward erosion is a direct consequence of back flow circulations characterized by relatively high-flow velocity and sometimes strong wave motions. As the erosion develops, the main flow direction in the spillway channel shifts somewhat towards the eroded area. The circulation zone increases, which in turn aggravates the headward erosion. The limiting structures play a role in the toe erosion development. Although certain conditions may indicate a predisposition to headward erosion, the risk does not necessarily exist in all dams. The risk for toe erosion has been identified for Porsi and Halvfari, but not for Långbjörn and Höljes. Despite of serious erosion downstream, relatively calm water with insignificant wave motion are characteristic of the flow pattern at the dam toe of the latter two dams.
Place, publisher, year, edition, pages
IdentifiersURN: urn:nbn:se:kth:diva-179764OAI: oai:DiVA.org:kth-179764DiVA: diva2:889419
24th ICOLD Congress, June 2012, Kyoto, Japan
QC 201601072015-12-242015-12-242016-01-07Bibliographically approved