EVALUATION OF SEEPAGE, SLOPE STABILITY AND DEFORMATION IN AGUATWUHA EMBANKMENT DAM UNDER STATIC AND DAYNAMIC CONDITION, AMHARA REGION, ETHIOPIA

Abstract

Embankment dam should be stable under all loading conditions and operations due to its susceptibility to hydraulic, seepage and structural failures. Aguat wuha embankment dam has been affected by high water loss through the dam body especially around the periphery of the out let and downstream slope face erosion. This study was conducted to evaluate seepage, slope stability, and stress deformation performances under all loading condition. In this study, field measured data and GeoStudio2012 model was used to analyse seepage, slope stability and stress deformation of the dam under different cases of reservoir operation conditions. Leakage flow rate, pore water distribution and location of the phreatic line were determined using the finite element (FE) software, SEEP/W. The slope stability evaluation utilizes limit equilibrium (LE) based software (SLOPE/W). The stress-deformation was analysed using the FE models, SIGMA/W software. The stability analysis results indicated that the critical upstream and downstream slope of the dam is safe within the prescribed USACE range of factors of safety for all loading causes and operations. In addition the stress deformation results of vertical settlement and horizontal strain showed that the impervious core material is safe against the inside cracking due to the vertical and horizontal displacement and the dam could not be affected by overtopping problem due to vertical settlement .But, in cause of seepage the result showed that the simulated results of SEEP/W software show that the average flow rate of leakage for the entire length of the dam at Elevations 2874 m a.m.s.l and 2868m a.m.s.l reservoir level was equal to 1.17*10-5 m3 /s and 5.51*10-6 m3 /s respectively; whereas the actually measured seepage at the downstream of the dam body was 6* 10-3 m3 /s and 4*10-3 m3 /s at elevations 2874 m and 2868 m reservoir water level respectively which is much higher than the simulated one. From this we can conclude that the dam is exposed to seepage and downstream face erosion and may the dam lead to failure. Therefore, remedial measures should be taken before the dam fail and cause damage of life, property and investment of the downstream.