Seismic stability assessment of an arch dam-foundation system

Abstract

A seismic stability assessment of arch dam-foundation systems is presented using a comprehensive approach, in which the main factors that significantly influence the seismic response of an arch dam-foundation system are considered. A large scale finite element model with over 1 million degrees of freedom is constructed for the Baihetan arch dam (289 m high), which is under construction in the Southwest of China. In particular, the complicated geological conditions with faults intersecting interlayer shear weakness zones at the dam base and the dam abutment resisting force body is modeled in the analysis. Three performance indices are adopted to assess the seismic stability of the arch dam. The results demonstrate that the opening of the joints of the Baihetan arch dam is small and the water stop installed between the joints would not be torn during a design earthquake. The yielding formed in the interface between the dam and foundation does not reach the grouting curtain that would remain in an elastic state after an earthquake. The yielding zones occurring on the upper portion of the dam faces extend 1/8 thickness of block section into the dam body and thus cantilever blocks need not be concerned with sliding stability. The faults and interlayer shear weakness zones in the near field foundation exhibit severe yielding, and a potential sliding surface is penetrated. Although the factor of safety against sliding of the surface fluctuates with a decreased trend during an earthquake, the minimum instantaneous value reaches 1.02 and is still larger than 1.0. Therefore, a conclusion is drawn that the Baihetan arch dam-foundation system will remain stable under the design earthquake.