Seismic Displacement Analysis in Kulekhani Rockfill Dam

In seismically active zones like Nepal, dam design and analysis must prioritize the ability to withstand large deformations, especially under dynamic excitations caused by high seismic activity. The region's intense earthquake accelerations significantly amplify structural responses, revealing pronounced nonlinear behaviour. To capture and predict this nonlinear behaviour, an equivalent linear model is applied. The higher ground motion impact assessment through FEM on a dam is a prerequisite analysis before construction. The acceleration time history of horizontal ground motion, including a highest peak of 0.6g, felt in the Kulekhani Reservoir rock-fill dam, during the Earthquake 2015 in Nepal, was evaluated using Geo-studio. The equivalent linear model (ELM) together with the Newmark approach for a sliding mass were considered during the simulation, to evaluate the permanent displacement in the dam due to earthquake acceleration. The vertical displacement at the crest was evaluated and compared with the post-event field observation. The maximum vertical settlement was found to be comparable with the observed 10 cm of subsidence. The study shows that the crest is at higher risk of subsidence during the ground motion. The slope displacement over the dam's upstream and downstream sides was tested considering a critical slip circle through the Newmark approach. The higher displacement was observed almost 4.8 times on the dam's downstream side compared with the upstream side, indicating that the higher horizontal positive peak ground motion affects more in the downstream slope rather than the dam's upstream side. In this case, the reservoir water load was found to be stabilizing the upstream slope. However, the study concluded that the Newmark approach overestimates the displacement compared with the field observations. The only noticeable rip-rap boulders were found to be shifted in the field during post-event observation whereas 0.72m of potential sliding mass is obtained from the simulation.