Abstract
For modern high earth dams, sufficient safety margin is considered in the designs of flood discharge capacity and dam crest elevation to prevent flood overtopping. However, for high earth dams which may induce catastrophic consequences, during their long operational period, extremely hazardous scenarios which could occur and threaten dam safety need to be considered. For the earth dams located in areas with intensive seismicity, there is a possible scenario that the release structures fail due to seismic landslides and gate failures caused by a severe earthquake when the flood begins to enter the reservoir. Thus, it is desirable to investigate the influence of failure duration of release structures on dam overtopping risk. Based on the Bayesian network, a methodology for overtopping risk analysis of earth dams considering effects of failure duration of release structures is proposed. The overtopping risk of the PBG earth-rockfill dam was analyzed to illustrate the methodology. The critical release structures which dominate the dam overtopping risk are identified. The dam overtopping risk is most sensitive to the failure duration of the spillway. The tolerable failure duration of the spillway is approximately 3 days, and when the failure duration of the spillway reaches 4 days, the dam overtopping risk drastically rises to an unacceptable level. The case study suggests that the proposed methodology could be helpful to analyze the influences of possible failure durations of release structures on dam overtopping risk and could facilitate preparation for emergency plans.
Highlights
Dams are important infrastructures for water resources management. ere are more than 98000 dams in China, among which earth dams are more than 80000 [1]
Erefore, the overtopping risk of the dams under normal operating conditions is quite small, if an extremely strong earthquake in the flood season leads to failure of the release structures and the flood discharge function of the release structures cannot be restored in time, dam overtopping may occur. us, for the earth dams located in areas with intensive seismicity, especially in the flood season, it is necessary to consider the impact of the failure of release structures caused by seismic landslides on dam overtopping risk. e important effect of the unavailability of the spillway on dam overtopping risk has been investigated (e.g., [28,29,30,31])
Based on the Bayesian network, a methodology for overtopping risk analysis of earth dams considering effects of failure duration of release structures is proposed in this paper
Summary
Dams are important infrastructures for water resources management. ere are more than 98000 dams in China, among which earth dams are more than 80000 [1]. Based on the Bayesian network, a methodology for overtopping risk analysis of earth dams considering effects of failure duration of release structures is proposed in this paper. Since this study focuses on the effects of failure duration of release structures on dam overtopping risk and the effects of uncertainties in other affecting factors (such as flood, reservoir characteristics, initial water surface level, and dam height) have been well investigated as mentioned above, only the uncertainties in seismic landslides, gate failure, and failure duration of release structures are considered in the analysis. (d) Considering the influence of failure durations of the release structures, reservoir routings are implemented and the conditional probabilities of dam overtopping are determined. Reservoir Routing considering Failure Duration of Release Structure and Conditional Probability of Dam Overtopping. Where the failure durations of the release structures are represented by t1, t2, . . . , tn, and HC is the dam crest elevation
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