Slope Stability Analysis and Mitigation Measures of the Agoro – Shahgubi Section of the Agulae - Berhale Road, Northern Ethiopia.

Abstract

The general objective of this research is to evaluate the slope stability and erosion problems along Agoro-Shahgubi section of Agulae-Berahle route and recommend mitigation measures. Disturbed soil samples and dimensions of the failed slopes (length, width and slope height) were gathered from nine failed slopes spread through Agoroshahgubi. Direct shear tests were performed to determine the shear strength of the soil samples. Having the results of unit weight and direct shear tests the stability of the slope was checked. The slope stability analysis method using SLOPE/W software has been used to determine the factor of safety of the slope. The results of the limit equilibrium methods shows that factor of safety is almost less than unity for almost all except for the Bishop method for the failed slopes for both sample codes A-1-01 and SG( this is why there are large boulders with the soil which acts as a supportive structure can may fail during rainy season ). So that the numerical results of the Limit equilibrium method verify instability of the slope. The major causes of slope instability in the study area are method of excavation, over steepening of the slope, deforestation and surface water erosion which includes the effect of saturation on strength. Based on the findings the following mitigation measures had been recommended which includes Removing of unstable and over hanging boulders, cut and fills solution (slope flattering and incorporating of benches in the slope and providing support (construction of retaining walls have been considered as a remedial solution.