Seepage and Stability Analysis of Durgawati Earthen Dam: A Case Study

Abstract

Analysis of dam slopes is of much importance because its failure may prompt loss of lives and properties. In this paper, both seepage and slope stability analyses of the earthen embankment dam of Durgawati reservoir project in the region of Kaimur–Bihar is presented. The analyses are performed using geotechnical software GEOSTUDIO 2007 (SEEP/W in Seepage analyses, Software permitted for limited period of use by GeoSlope Office, Canada, 2007; SLOPE/W in Stability Analysis, Users guide version 5, GeoSlope Office, Canada, 2002). Two sections of the Durgawati reservoir project have been considered for detailed stability analysis namely one from RD 640.09 m CH 21.00 and another from RD 670.57 m CH 22.00. Both upstream and downstream slopes, located at the dam site have been investigated for long-term stability for full reservoir condition (i.e. steady-state seepage) and drawdown condition (i.e. transient-state). It has been observed that the Factor of safety against slope failure at the upstream face is substantially greater than that of the downstream slope because of resisting effect of the reservoir water on the upstream slope. The stability of the upstream slope of the dam decreased considerably during drawdown condition. The structure lies in the earthquake prone area Zone III as per IS 1893-2002. Therefore, a pseudo-static analysis has been performed using different horizontal earthquake coefficient in combination with both steady-state as well as transient-state seepage condition.