Geotechnical, geological investigation and slope stability analysis of landslide site in Eruh district of Siirt province

This study investigates the engineering geology, geotechnical properties and slope stabibility conditions of a region affected by landslide in Eruh County of Siirt Province. In order to determine the horizontal and vertical changes of the soil and the engineering, lithological and geological characteristics of the soil, three drilling and drilling studies were carried out in total 60 meters. The survey area consisted of topsoil, middle-upper Miocene ged very loose and non-homogeneous, partly marn added, arenaceous, ballast, low-silt clay units. Standard Penetration Test (SPT) was performed in order to determine the physical and mechanical properties of the soil layers in the drilled wells. In addition, distributed (SPT) and undistrubuted (UD) samples taken from boreholes were subjected to soil natural unit volume weight, water content, sieve analysis, Atterberg limits, consolidation and three-axial pressure tests. LL (Liquid Limit) average 57,8 %, PI (Plasticity Index ) 32,3 % of the samples were calculated. Swelling degree was found to be high and swelling percentage as 20- 30 % according to plasticity index. Safe bearing capacity by considering factory of safety three was found as; 1,038 kg/cm² for SK-1, 1,027 kg/cm² for SK-2, and 1,080 kg/cm² for SK-3. Slope Stability Analysis was used in the landslide in the study area. Any groundwater was not found during drills in the survey areas within the scope of the study. However, establishment of a drainage network is recommended in order to prevent leak water and rainwater as there might be a risk of liquefaction since the unit consists of nonhomogeneous sections dissolving in water, and as the unit is very loose and swelling, and soil is loose up to 20 meters. The inclination of the total area of landslide zone within the survey area is between 45-50 %. The landslide zone was found to have high-level Factor of Safety (FoS) in the slope stability analysis computations. Beside the survey area constitutes a risk as the region receives high amounts of precipitation, and the unit causing landslide consists of very loose non-homogeneous, arenaceous ballast low-silt clay layers.