Analysis of stability and global sensitivity of earth-rock dam slopes: a case study of Rib dam, Ethiopia

This paper aims to analyze the stability of Rib dam slopes under varying reservoir water levels and drawdown conditions, considering sensitivity factors and their interactions. The dam is a zoned earth-rock dam constructed in the Tana basin, Ethiopia. The study utilized a combination of finite element and limit equilibrium methods to assess global sensitivity factors affecting zoned earth-rock dam slope stability. Statistical and regression analyses were then employed to identify critical influencers on the factor of safety of the dam’s slopes. The research involved analyzing one zone and all zones of the dam at a time, considering seepage and flow stresses. Results showed that factors like internal friction angle significantly impacted slope stability. Regression models were developed to predict safety factors based on drawdown time, reservoir water levels, and soil-rock parameters. Findings suggest that factors like internal friction angle play a crucial role in dam stability, with rapid drawdown conditions posing a risk to the upstream slope stability. The study provides insights into the importance of various factors in dam slope stability, aiding in determining appropriate design and stabilization measures.