SEEPAGE AND SLOPE STABILITY ANALYSIS OF EMBANKMENT DAM BY USING GEO-STUDIO AND PLAXIS 2D MODEL: THE CASE STUDY OF AMERTI- NESHE EARTH FILL DAM, OROMIA, ETHIOPIA

Abstract

The analysis of seepage and slope stability is an important activity to set the safety of the dam. This study performed the analysis of seepage and slope stability of Amerti-Neshe earth fill dam. For this study, Geo-studio and Plaxis 2D software’s were used for the analysis of seepage and slope stability of the dam at different reservoir loading conditions. Seepage flow rate and pore water pressure distribution were determined using SEEP/W and Plaxis 2D software’s. The slope stability analysis uses limit equilibrium based (SLOPE/W) and Finite element based (Plaxis 2D) software’s. The slope stability analysis result solved by SLOPE/W based on Morgenstern-price and Plaxis 2D based on Mohr-coulomb elastic-plastic model method was compared with the predetermined values by experienced Company and the design document of Mid-south design and research institute. The seepage flow rate result through the embankment body and foundation of the entire dam length from both software's shows that at maximum pool level by SEEP/W is 0.009828948 m3/sec and by Plaxis 2D is 0.003020906 m3/sec, at normal pool level by SEEP/W is 0.005678 m3/sec and by Plaxis 2D is 0.006882064 m3/sec When the maximum acquired value from the model was compared with the predetermined value by Liews, 2014, which is 0.83m3/sec for the satisfactory site and the total seepage value obtained from the design document of Mid-south design and research institute. 0.0086m3/sec is the maximum flow rate value obtained from each model which is less than the upper limit of recommendable value which makes the result with in the safe range. under all reservoir loading condition the phreatic line passes through the horizontal blanket this indicates as the dam was safe from the point of view of seepage for an acceptable site and making the site secures. Finally, the dam's stability analysis of each slope was calculated using the Slope/W and Plaxis 2D software under various reservoir loading conditions and the result was compared with the minimum acceptable safety factor provided by experienced companies like USBR and calculated minimum factor of safety of the design document of Mid-south design and research institute. then obtained results from both software shows that as the dam was safe.