The stability analyses of unsaturated soil slopes affected by rain infiltration

Slope failures lead devastating results to both human lives and country economy. Rain infiltration is one of the major reason for slope instability. Moreover, the instability of unsaturated soil slopes during wet periods is common throughout the world. Rain infiltration causes to arise perched water table, increase the groundwater level or/and leads to rise pore water pressure resulting decrease in matric suction. This, results in a decrease in shear strength of soil and may even end up with failure. To prevent such problems; landslide mechanism of unsaturated slopes under rain infiltration need to be studied in detailed. This study mainly consists of three steps including site investigation, laboratory works and modeling with GEOSTUDIO software. In site investigation, the site which is located on the Southeast Anatolian Thrust Belt was observed by opening research pits and taken undisturbed soil samples from ophiolitic clay soil by pushing the sample tube into the soil. Properties of saturated soil such as effective shear strength parameters (cohesion and angle of internal friction ), the coefficient of permeability were found conducting laboratory and field tests and also obtained the soil-water characteristic curve, hydraulic conductivity and initial matric suction of soil using filter paper method. Finally, the unsaturated soil slope stability analyses under rain infiltration were done using SEEP and SLOPE modules of GEOSTUDIO. In addition, parametric analyses were done to understand the effects of permeability, rain intensity and duration, initial groundwater level on the stability of unsaturated soil slopes. As a result of the analysis, changes in the factor of safety have been obtained and it is seen that all the parameters have effects in varying degrees of the slope stability.