SLOPE STABILITY ANALYSIS OF RAINFALL INDUCED LANDSLIDES: A CASE STUDY ON GOHATSION - DEJEN ROAD ABAY GORGE

Slope failures triggered by rainfall are causing considerable damage and loss of life every year throughout the world. During rainy seasons landslide in Abay gorge has been causing: loss of human lives, failure of engineering structures, and damage on agricultural lands. This is due to the fact that, at dry seasons the ground can develop considerable amount of suction and this improves the shear strength of the soil in the area. In rainy season, when rainfall infiltrates into ground, suction decreases, while the shear strength also reduces, which may lead to slope instability. In this study, a landslide at 10Km from the town of Gohatsion has been selected as a case study considering risk for road and hazard score values and the availability of the required data for the stability analysis. The required data for stability analysis were collected from fieldwork measurements and observations and from secondary sources mainly GSE and ERA. A detail slope stability analysis was carried out based on limit equilibrium approach using SLOPE/W. Seepage analysis for the stability analysis were conducted by adopting finite element based software, called SEEP/W. The relationship of rainfall and slope stability was demonstrated by conducting the analysis for different rainfall durations and intensities. The coupled hydro-geological stability analysis result reveals that, loss of suction due to rainfall infiltration is critical for the stability of landslide at 10km sta. The factor of safety during the rainy season shows significant reduction from its initial dry state value of 1.506 to 1.29 after 3-day rainfall duration. Finally, based on the stability analysis findings concluding remarks on the application of the study in landslide prediction and recommendations for further studies were clearly stated