Risk assessment for rockfill embankment dams

Offentlig prosjektsammendrag

Norway has over 400 embankment dams, of which a majority are rockfill embankment dams. Most of the Norwegian dams were constructed during the period 1960-1990, and are still producing hydropower, a much needed renewable energy ressource. Hydropower is an essential source of income in Norway's economy. Many of the rockfill dams are "Large Dams", and would result in intolerable consequences if massive overtopping of the dam crest should occur. The dams are to be used for another 50-100-150 years. The dams have aged since their construction, and there is a need today to develop a streamlined methodology to reevaluate the safety of the dam in terms of risk to the population and material property downstream. Experience gathered over more than 100 years show that the most frequent cause of a rockfill or earthfill embankment dam failure is internal erosion and piping (water gradually digging destructive channels through the core and/or filters, and then through the rockfill). The project develops a streamlined method to do risk assessment of rockfill embankment dams, with focus on failure due to internal erosion and piping. The methodology includes the evaluation of the risk reduction of risk mitigation measures. Recommendations for acceptable and tolerable risk levels for dams will be developed.