Abstract: “A concrete gravity dam is a major hydraulic structure which resists all external forces by its weight. Consideration of earthquake force is a major concern for the construction of major structures like dams. The main objective of this study is to obtain the design base width of a dam for different seismic conditions by varying the earthquake coefficients in both vertical and horizontal directions. This has been done by equating the different factors of safety for a dam with their limiting conditions under both tail water and no tail water condition. The shape of the Mettur dam in India is considered for the study. In the study the base width was calculated using Newton Raphson method in C++ and their variation plotted. A study on the variation of uplift pressure with change in the position of drainage gallery and the total uplift force and moments were obtained. A comparison was done in the design base width obtained for a particular case of earthquake without drainage g allery to the”

Keywords: Base Width, Horizontal Earthquake Coefficient, Tail Water, Uplift, Vertical Earthquake Coefficient