Estimation of permanent displacements of the Tehri dam in the Himalayas due to future strong earthquakes

Abstract. The objective of this paper is to estimate permanent displacements of Tehri dam due to an earthquake of magnitude Mw = 8·5, the occurrence of which has a high probability in the region, and for an earthquake of magnitude Mw = 7·0, for which the dam has been currently designed. A two-dimensional finite element analysis and five different semi-empirical and empirical methods, like, Seed and Makdisi’s method, Newmark’s double integration method, Jansen’s method, Swaisgood’s method and Bureau’s method have been utilized to study the probable dynamic behaviour of the dam and their results are compared to get a range of values within which, the permanent displacement of the dam, is estimated to lie. The present study shows that the predicted displacements due to an earthquake of magnitude Mw = 7·0 are significant but not enough to compromise the safety of the dam. However, the displacements predicted for an earthquake of magnitude Mw = 8·5 are quite high and might cause rupture of filter zones. The maximum deformations (755 cm for Mw = 8·5 and 43 cm for Mw = 7·0) are predicted by Seed and Makdisi’s method while the minimum deformations (14 cm for Mw = 8·5 and 2·5 cm for Mw = 7·0) are computed by Jansen’s method