SLOPE STABILITY EVALUATION OF AN EMBANKMENT DAM: THE CASE OF PROPOSED CHALCHAL EMBANKMENT DAM, BALE ZONE, ETHIOPIA

Abstract

One of the most important factors that can be considered when it comes to assessing the safety of an embankment dam is its slope stability. This study was conducted to analyse the Chalchal embankment dam located in south east Ethiopia and aims to come up with a list of helpful measures to prevent incidents. Geostudio-2018 software was employed to analyse the seepage using SEEP/W, and SLOPE/W for slope stability analysis under different cases of operations. Results of seepage analysis using SEEP/W was utilized as a parental input for the analysis of SLOPE/W models. In this study, Seepage analysed to determine seepage flow rate in dam body and foundation, pore water distribution and location of phreatic line using the SEEP/W. Slope stability analysis was performed for the critical slopes using the limit equilibrium method SLOPE/W software based on the Morgenstern-Price method of safety factor. The stability evaluation results indicate that the critical upstream and downstream slope of the proposed dam is not safe within the prescribed USACE factors of safety for the possible loading and operation cases. This necessitates proposed dam stability optimization to improve slope stability problem. Based on the research findings removal off Alluvial deposit and replacing with material with friction angel greater than 280 to solve slope stability problem of the dam, wise use of construction material is very important because of huge volume of construction material is needed in quality and quantity, clay quarry site around the project is varying in depth and in quality as a result clay blending with each other is essential during construction. Providing fine filter in between clay core and general foundation is essential to protect clay particle movement to the foundation. Soluble rocks and sandstone rocks when thinly bedded and well jointed as in the case of the study area, can lead to thoughtful problems mainly in terms of shear strength and water-tightness. Therefore, reservoir clay blanketing on the upstream river section is critical to reduce seepage to the foundation. Seepage and load deformation analysis will be the future research area.