A new method for dynamically estimating long-term seepage failure frequency for high concrete faced rockfill dams

Failure frequency of a dam varies greatly with reservoir water level and time. It is important but difficult to dynamically estimate failure frequency of high concrete faced rockfill dams (CFRDs) merely based on the probabilistic approach due to limited failure cases of high CFRDs. In this study, a new method is developed for dynamically estimating the long-term revolution of seepage failure frequency of high CFRDs by combining an analogical approach with the Bayesian approach. A simple and precise seepage generalized method and a parameter named defect parameter are introduced to provide the basis of comparison between the dam of interest and the accumulated database of high CFRDs. Using the cumulative probability distribution from the database, the correlation between annual seepage failure frequency and defect parameter is established. A high CFRD case in China with an operation history of slab breakage and reinforcement is selected as an example to illustrate the applicability of the new method. It is verified that the variation tendency of safety level of high CFRD is well simulated through the annual seepage failure frequency calculated by the newly proposed method.