ANALYTICAL EVALUATION OF NATURALLY EXISTING SLIGHTLY WEATHERED ROCK AGAINST BLASTED ROCK AS EMBANKMENT MATERIAL (A CASE STUDY OF RIBB DAM

Abstract

Fundamentally, a good embankment dam design should not only refer to the one which is structurally stable and safe. However, it should also comprise of the actual site condition like use of easily available materials for construction purpose. Utilizing of locally available material for embankment dam will have economic advantages avoids construction difficulty and shortens construction periods. Ribb rock fill dam was designed and constructed with a significant volume of rock material produced by blasting and further degrading process to satisfy the gradation requirements. However, the site was rich with a slightly weather fine rock fill material which can easily be produced and stock pilled with normal production process of using machineries. Hence, this thesis presents the overall stability analysis for revised Ribb dam replacing the rock fill material with slightly weathered rock to show the effect of shallow geotechnical investigation works on dam projects. Numerical modeling software called GEO-Studio 2007 has been used for the analysis. Based on the analysis carried out for different loading conditions, the revised section satisfies all the requirements suggested by standards and improved factor of safeties of 1.801 for steady state seepage, 1.489 for sudden draw down and 1.396for steady state with earthquake has been found. Besides the newly revised design has been found economical since saves 497,536.439.19ETB, less difficult for construction and considerably shortens construction period.