Geotechnical investigations for landslide hazard and risk analysis, a case study: the landslide in Kojour Region, North of Iran

In this article, the occurred landslide on the 27th kilometer of Kojour pathway, in the west of the Gat-e Kash village was surveyed and studied using geological maps, aerial photography and satellite images of the region. According to field investigations, this landslide is a transitional slide that occurred on Cretaceous marl successions near the Khachak over thrust fault and the Zanou’s river. Seven factors including lithology, topography, distance from fault, climate, land use, hydrology and hydrogeology and engineering geological conditions of the sliding mass were recognized and analyzed as effective parameters in the landslide. Based on engineering geological studies, the soil of the landslide is laid in SM-SC classes of the Unified Soil Classification System and has low swelling potential. The obtained safety factor by limit equilibrium stability analyses method indicated that the slope is stable in the present condition, but by changing in effective factors it may take place to unstable conditions again. The results of regression analyses showed the safety factor of the landslide is more controlled by specific gravity and degree of geomaterial saturation. During the field investigation, some sections with high potential of sliding were recognized; therefore, the most effective method including vertical and horizontal drainage and Gabion wall were offered for stabilization of the slope. Environmental assessments of the landslide were analyzed by the clustering technique, that negative impact was seen on soil erosion, surface and ground water quality, agriculture, road and communication.