EVALUATING THE STABILITY OF EMBANKMENT DAM BY INTRODUCING CONCRETE FACE ROCK FILL DAM (CASE OF LEGEMERA DAM SOUTH WOLLO, ETHIOPIA)

Abstract

Design of an embankment dam is a vital issue from the standpoint of safety, economy, controlling seepage, and speed of construction. Concrete face rock fill dams (CFRDs) virtually impervious, resistant to erosion and aging, workable, shorter period of construction and small volume of construction material. It is very well suited when there is no ample amount of impervious material within economically feasible hauling distance and severe weather conditions during construction. This study was aimed at addressing biggest challenge of hauling distance of the impervious clay core material by changing earth fill dam with central clay core to concrete face rock fill dam in case of Legemera micro earth dam, found in South Wollo. Universally recommended standard values beside to primary and secondary data essential for the work has been used. GeoStudio 2012 software was used for stability, seepage and deformation analysis of the dams. Consequently, by using this software good result of safety factor has been found for concrete face rock fill dam with regard to stability of the dam during maximum pool level, steady state condition and end of construction. During steady state condition, the upstream and downstream factor of safety computed for the dam is 1.954 and 1.544 respectively. Likewise, at the end construction, the upstream and downstream safety factor is 1.824 and 1.59 respectively. The seepage is also reduced to values of 2.42 x10-6 m 3 /sec by implementation of concrete face rock fill dam. Economic analysis result similarly shows that, concrete face rock fill dam is more economical by saving 22,441,387.75 ETB due to fast rate construction of the dam independent of weather condition. Generally, application of CFRD can fulfill the basic requirement and minimum factor of safety under all loading condition, and dam of such types is seepage free