Browsing by Author "Abera, Kisanet"

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    Application of Integrated Geophysical Techniques for Landslide Investigstion Along the Arbaminch-Gidole Road in Derashe Wored, Snnp,Ethiopia
    (Addis Ababa Universty, 2016-06) Abera, Kisanet; Mewa, Getnet (PhD)
    This research was conducted to assess the landslide problems occurred in Welaite Kebele located along the Arbaminch-Gidole Road, in Derashe Special Woreda, SNNP. The specific purposes were to determine the extent of the landslide affected zone, identify the triggering factors/ mechanisms, including mapping tectonic features. For these purposes Electrical Resistivity (with Vertical Electrical Sounding modification) and Magnetic methods of prospecting were utilized along specific lines. From the survey results it has been possible to delineate three distinct lithological units with contrasting electrical properties. Accordingly, the top layer with variable resistivity (43-77 Ohm) has a thickness range of 0-60m and it is associated with the response of colluvial deposit. The intermediate layer is highly conductive (2-32 Ohm-m) and relatively very thick (150-200 m) and attributed to the effect of a highly weathered and decomposed volcanic rocks which is well saturated. The substratum is marked by very high resistivity values (1400-10,000 Ohm-m) and it is delineated below the depth range of the second layer, i.e. 175-250m. Thus from these results the morphology of the major failure surface, which is between the contact of the second and the third layers, is clearly outlined. It shows a SE dipping trend with gentle dip angle - . In addition, both the resistivity and magnetic survey data have equally suggested the possible presence of structurally disturbed zones around VES10, VES14, VES16, as well as VES4. These features are assumed to play their role in the process of mass sliding. Based on the collected data analyses it became clear the road to Gidole is aligned over a deeply landslide affected zone, where along with the steeply dipping surface topography, the lithologic units are weak and highly saturated by groundwater and also affected by tectonics. Therefore, construction of road and other infrastructures require careful consideration of these real site conditions.