Numerous dams serve to supply the population with energy and drinking water. Dam structures include not only retaining walls surrounding wide valleys, but also earth dams, which fit harmoniously into the landscape and at the same time can be economically erected. Retaining structures need to be provided with proof of earthquake resistance due to their high degree of relevance. The earthquake return period has to be selected in accordance with the existing dam structure class.
The safety verification of the dam stability can be investigated with a finite element model on the basis of the Krey-Bishop procedure with the assumption of circular sliding surface. In case of an exact calculation, a time history analysis is executed, in which the state of stress within the dam is recalculated at each time increment. Thereafter the decisive sliding circle is determined on the basis of the state of stress at each time step, by comparing the retentive and impulsive forces along the sliding circle. The forces are calculated by integrating the stresses from the finite element model along the regarded sliding circle.
Pseudo-static procedures can also be applied as an alternative. When calculating dam structures, one can work with two-dimensional calculation models as long as the curve of the dam wall is only moderate. Otherwise, three-dimensional models need to be taken into account. In some cases, the soil-structure-interactions effects must be considered in order to avoid the occurrence of wave reflection in the models. SDA-engineering GmbH gained extensive experience with safety verification of dam structures in the scope of diverse former projects.