Analysis of rock slope stability for Mohmand Dam - A comparative study

This study presents a framework for semi-empirical slope stability analysis of Mohmand dam, an important ongoing mega concrete-faced rockfill dam hydropower project in Pakistan. The project comprises of 213-m-high hybrid dam that will produce 800 megawatt of clean hydropower energy in addition to an effective flood mitigation. Also, it will supply water for both irrigation and drinking to the provincial capital city, Peshawar. In this study, finite element and limit equilibrium methods (LEM) have been used for slope stability analysis and factors of safety have been computed for all anticipated loading conditions including earthquake loading. The rockfill samples of main dam were obtained from the construction material site of Mohmand dam and the input parameters for slope stability analysis were obtained both empirically and through laboratory testing. Results of both limit equilibrium and finite element analyses have been compared, and it was observed that the latter is more conservative than the former giving 11%-19% lower FOS as compared to the FOS obtained through LEM, except for earthquake loading. The implications of current findings have been demonstrated using an important case study of an independent dam site that would boost the confidence of practitioners.