Numerical analysis on the influence of dynamic soil-structure interaction in Soria Arch dam: A case study

Abstract

Soria arch dam and reservoir is the largest infrastructure of this type that exists in the Canary Islands both in capacity and height which is located in the Island of Gran Canaria. The goal of this paper is the development of a numerical model for the analysis of the dynamic and seismic behavior of this arch dam. To do so the effects of the ground motion and of the canyon geometry on the dynamic response of the arch dam are studied in this paper. The seismic response of the arch dam subject to time harmonic shear waves impinging the dam site with a horizontal upstream and cross-stream free-field ground surface motion is analyzed. The numerical model includes both the concrete arch dam and the surrounding area, so that soil-structure interaction phenomena can be taken into account as accurately as possible. The model is used to evaluate the magnitude of soil-structure interaction and also the influence of the accuracy of the geometrical representation of the surrounding topography on such soil-structure interaction effects. To this end, two different numerical models are built. On the one hand, a Finite Element Model of the actual geometry of the concrete dam wall is developed and used to perform a modal analysis of the fixed-base model. On the other hand, several three-dimensional frequency-domain Boundary Element models of both the concrete dam and the surrounding topography are built; all of these models include the actual geometry of the dam wall and different approximations of the surrounding soil, ranging from a very simplified straight prismatic canyon to an elaborate model of the actual topography. These BEM models are used not only to estimate compliant-base natural frequencies and mode shapes, but also to study the seismic response of the system when subjected to incident planar seismic waves. The results show that the influence of the soil-structure interaction effects on the dynamic response of the system is quite significant. It is also shown that the asymmetry of the canyon might significantly affect the seismic response of the dam wall.