Embankment Dam Seepage and Slope Stability Analysis: The Case of Arjo-dedessa Dam, Ethiopia

Dams have one of the greatest significant roles in operating water resources. Seepage and slope stability failures cause completely failure of embankment dams. Dam disasters not only hazard community safety, they also can cost our economy millions of dollars in compensations. The study area is found in Oromia regional state between East Wollega and Bunno Bedele Zone. The dam is located on Dedessa River, tributary of Blue Nile River. Analysis of seepage quantity was done by Darcy’s phreatic line, and SEEP/W software model for both homogeneous and zoned dam. The expected quantity of seepage estimated with the SEEP/W software model analysis that includes foundation seepage is 6.6*10-6m3/sec. Slope stability study is to contribute to the safe and economic design of upstream and downstream slope of the dam. The factory of safety obtained by Morgenstern-Price method for end construction is (FOS=1.99), for steady state (FOS=2.03) and rapid drawdown (FOS=2.91). However, at the design document shell material hadn’t been designed properly. Finally the paper concluded that the likely corrective measures for seepage controls are impermeable blanket, grouting, and the downstream slope miscarriage by eliminating the pathetic zone and seal with like graded quantifiable, regular repairs and shield the downstream slope with grasses.