SEISMIC ANALYSIS OF EMBANKMENT, EARTH AND ROCK-FILL DAMS

Abstract

An efficient design of an embankment dam should be free from risk and should be economical. The structure designed shall be durable and do not require any maintenance. The structure should also serve the subject of intention for which it is designed. Embankment dams have a lot of advantages over Gravity dams. The Embankment Dams should be designed to withstand ground shaking due to earthquake. The construction and design of embankment dams have undergone great changes over the years. In this dissertation, linear analysis of self-weight of embankment dam is performed and the present study result are compared with the resulted reported by the Acar et al. (1988). Vertical stresses along the symmetry axis of embankment and stresses along the base of Embankment Dam are obtained and compared with those presented by Acar et al. (1988). Seismic Analysis is performed on the same model on which Static Analysis is done by applying Acceleration time history of 1999 Chamoli Earthquake. In past, devastating damages due to earthquakes in the Himalayan region has been observed. The state of Uttarakhand is situated in the Himalayan foothills, and it is under high seismic zones (IV and V) as per IS 1893 (2016). Tehri Dam a unique example of Earth and Rockfill dam, located in Uttarakhand, it is also the tallest dam in India, which experienced many earthquakes e.g., 1991 Uttarkashi earthquake and 1999 Chamoli earthquake. In the present study, two-dimensional finite element analysis (2D-FEA) is carried out to investigate the behavior of Tehri dam under the 1991 Uttarkashi earthquake with Peak Ground Acceleration (PGA) 0.30 g. The viscous boundary is applied at the side of the FEA model and the bottom of the model is fully fixed. The 1991 Uttarkashi Earthquake was applied in the horizontal direction. Linear Elastic Model as well as non-linearity of the dam using, Mohr-Coulomb (M C)) model in PLAXIS 2D. A constant height of hydrostatic force is applied upstream, and seepage of water is allowed through the dam to downstream. The seismic response of the dam is represented in terms of horizontal and vertical displacement of the core.