Slope Stability Analysis of Earthen Dam under Seismic Loading

Researches in geotechnical engineering and day-to-day up-gradation in the earth moving machineries have enabled the construction of high earthen dams more easy and safe. With changing seismic conditions of the tectonic plates, it has become important to design each structure in a way it can withstand various earthquake conditions. Although, flexibility of soil material offers good seismic stability to the structures but stability of earthen structures depends largely on geometry, material properties and different conditions it has to bear during its design life. An earthen dam designed keeping all these aspects in mind, is a cost-efficient method of retaining water. This work is centered around the analysis of slope stability of a section of Durgawati Earthen Dam built in Kaimur district of Bihar. The study takes into concern the behavior of slope of the earthen dam under different drawdown conditions along with seismic conditions developed. Various methods have been developed for slope stability analysis but all have some or the other limitations. Thus, the exact behavior of the dam in real-time is not predictable. Here, a comparative analysis of conventional method and finite element method has been run. In the study, it has been found that the difference in conventional and finite element method can reach upto 40%. The change of factor of safety (FOS) in different situations gives us an overview of the crucial phase in dam's design life. With recent changes of tectonic conditions, the seismic analysis of structures as important as dams needs to be given more importance. For a safer and more cost efficient structure design, the limitations and advantages of both the methods need to be understood before we can move from the conventional method suggested in Indian Standards to a more developed method such as Finite Element Method.