Zuverlässigkeitsanalyse für die Staumauer der Diemeltalsperre
In Germany most gravity dams consisting of masonry between 1890 and 1920 were designed and built under assumptions which today do no longer satisfy the current technical standards. Therefore, many of these dams were adopted to current technical standards during the last years, in order to prove that their stability is according to present technical standards, regulations and rules. Although dams with their manifold water resources management contribute to the benefit of the society, they are critically regarded by the public because of environmental and safety aspects. The risk a dam constitutes for society can be determined by quantitative evaluation though, and may be objectively evaluated by the comparison to other risks. Thus this study is concerned with the introduction of the reliability analysis currently being developed which makes such a quantitative evaluation possible. The applicability of this method is clarified with the consent of the „Waterway and Shipping Directorate - Center” by the example of the Diemel dam. The Diemel dam is a representative example for a gravity dam, which is built in the beginning of this century and is adopted to current technical standards by safety measures. For every mode, that may lead to a dam failure, the reliability or rather the probability of failure is determined according to the first order reliability method. These modes as well as the structural and organizational measures taken in order to avoid or reduce damage are displayed in event trees. The reliability is assessed for each branch of the event tree. The overall probability of dam failure is determined by the combination of the reliabilities of all event trees. The stability of the dam is examined by conventional and numerical stability analyses under consideration of the stochastic nature of the variables. Two- and three-dimensional stability investigations for the dam were carried out under consideration of the interaction of structure and bedrock on the basis of models for the stress-strain behaviour and the permeability of jointed rock, which have been developed at the Institute for Foundation Engineering, Soil Mechanics, Rock Mechanics and Waterways Construction of Aachen Technical University, and which are implemented in the finite-element-programmes FEST03 and HYD03. Following potential modes of failure of the Diemel dam were taken into consideration: - failures in the masonry material: horizontal crack on the upstream face of the dam, overstressing on the downstream face of the dam, - failures in the dam body: tilting of the dam, - failures in the foundation: sliding of the dam, sliding of a wedge in the foundation, - emptying of the reservoir: piping at foundation due to erosion of joint fillings. The reliability of the dam was determined for a storage level corresponding to the normal water level and also for a water level at the crest of the dam. Additionally, the influence of ineffective grout curtains and drainages in the dam and/or foundation on the reliability was investigated. After considering every discussed mode, the reliability analysis for the cured Diemel dam leads to the conclusion that a failure of the dam can be entirely excluded. In addition, the positive effect of the modernization of the dam on its safety or rather its reliability were demonstrated by the results of this reliability analysis. Therefore, the reliability analysis represents an excellent method for the designers and holders of a dam as well as for the public to evaluate and quantitatively assess the danger, that such a structure holds for the public due to potential failure modes, by determining the quantitative value of the reliability.
info:eu-repo/classification/ddc/620, Ingenieurwissenschaften, Zuverlässigkeitsanalyse, Risikoanalyse, Standsicherheit, Staumauer, Probabilistik
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