The Role of Soil Chemical and Physical Characteristics in Landslide Occurrence (Case Study: Afsar Abad Area in Chaharmahal and Bakhtiari Province)

The Occurrence of more than 400 landslides in Chaharmahal and Bakhtiari province shows a special sensitivity against erosion in this terrain. To investgate the role of the soil physical, chemical and mineral properties on the occurrence of the landslides in Afsar-Abad, Do ab Samsami in the west of Chaharmahal and Bakhtiari, were drilled six boreholes in sliding boundary and safe restrictions on the quaternary Slope Colluvium. The sampling has done in three depths after profiles analysis. Physical properties such as bulk density, true specific gravity, saturation percent and soil texture along with chemical characteristics including organic matters, limestone, gypsum, dissolve cations were measured. The soil texture is silty clay loam in both experiment groups. The results are analyzed and interpreted through statistical methods. They show that there is a meaningful difference in the amounts of clay, organics, Silt, Ca, Mg, and EC of both control and experiment group. Silt has a direct relationship with landslide occurrence. Piping occurs due to the increase in the underground water level and subsurface erosion; consequently silt is washed away from the body of the soil. The increase of clay in the safe area can prevent earth-sliding. Thus, low or average amounts of clay in the soil lead to the stability of both soil structure and soil particles. This, in itself, prevents soil collapse. The amount of Ca has a reverse relationship with landslide. This shows the important role of this cation in increasing the stability of the soil structure, as well as the shear strength, and finally the earth stability against any rupture in the soil particles. The increase in the amount of EC in the sliding areas points out the effect of the dissolution of salts as Nacl and Kcl which is itself caused by the increase of the amounts of rainfall (about 900 ml a year) and consequently the increase of the underground water level. Thus, landslide could be prevented by chemical remediation.