A Case-Study of Slope Stability Analysis at the Left Bank of the Bujagali Hydro-Power Plant in Uganda

Slope instability occurred on the left bank, upstream of the Bujagali hydropower dam reservoir, triggered by increased River Nile discharge resulting from a significant rise in Lake Victoria water levels in 2021. Despite the slope reinforcement efforts undertaken in 2023, slope failure persisted, indicating active instability. As such, using numerical analysis with Plaxis plain strain 2D, the cause of slope failure after slope stabilization using CRGG technique was examined. An alternative slope stabilization technique, involving slope chamfering and reinforcement with reinforced concrete piles, was also investigated. It is observed that the CRGG technique (resulting FoS of 0.95) adds dead load to the slope and makes it more susceptible to failure than when the slope is not reinforced. The alternative method of chamfering the slope to reduce its self-weight, and reinforcement with reinforced concrete pile (FoS = 1.33) has proven the most effective slope stabilization option for this site. As such, this new method can be explored for implementation to protect the dam reservoir slopes from future failure and preserve the dam’s efficiency.