STABILITYASSESSMENT FOR FLOOD PROTECTION DYKE (A CASE STUDY OF ABA- SAMUEL PROJECT, ADDIS ABABA, ETHIOPIA)

Abstract

Slope stability is the fundamental activity in the construction of the embankments from soil material. Improving the engineering properties of locally available construction materials with economic concept is a crucial issue in the construction industry. Here in Aba-Samuel dyke embankment is traditionally constructed without any design considerations for seepage and stability. Hence, this paper is mainly focused to assess the feasibility and slope stability of dyke embankment through improving locally available earthen construction materials engineering properties. In this paper, the soil material for dyke construction was blended through four mix trials with different materials, and the properties of the soil were tested and checked for the competency of the dyke from the possible cause of failures after mechanical stabilization through blending with better materials. The soil laboratory tests were conducted four trials for the determination of both the index and engineering properties to identify the soil for dyke construction. The engineering properties of the soil considered in this paper were permeability and shear strength of the improved soil was conducted and seepage and slope stability analysis were done using of Geostudio-2018 software. The result indicated that the optimum mixed portion obtained from blending the locally available waste soil with better soil materials gave good characteristics for the dyke construction. The dyke performance was checked for empty and full water level condition. From empty condition the analysis gave FOS for trial mix-4 was the maximum value of 2.07 for 20% sand and 80% clay fraction. For trial combination of mix-4, steady-state and transient seepage were analyzed. For steady-state seepage the amount of water seeping through the dyke is 3.15*10-8m 3 /sec/m. and FOS for downstream part of the dyke gave 1.8.For transient seepage the analysis was done for 24 hr time period, the analysis gave seepage water decreases with time and at the end of 24 hrs it gave 2.99*10-8 m 3 /sec/m.Stability of the dyke at the upstream part for transient condition gave FOS at the end of time 24hrs. In conclusion, Aba samuel dyke embankment was better behaved with improved material with suggested blending ratio for seepage and stability through Geostudio software.