Sina Keshtkar - MSC Student of Civil Engineering, Islamic Azad University of Lahijan
Mir Ahmad Lashteh Neshaei - Associate Professor of Civil Engineering Department, Guilan University
Ebrahim Amiri - Associate Professor of Water Engineering Department, IAU of Lahijan

Stability of major structures located on clay foundation is one of the important subjects in the civil engineering. Stability of clay foundation is due to ground water penetration through porous media of the soil. Therefore, water level control and suitable drainage system can be so important to protect the foundation of such structures. Leaching in soils is the important subject in the geotechnical engineering. Leaching resulted in removal salts of soils and reduction strength and physical properties of soils. Lixiviation of soluble salts cause the change of physical properties as unit weight, void ratio, Atterberg Limit, hydraulic conductivity and specific gravity. As a result of becoming loose the soil structure, strength parameters are reduced. One of the effects of reduction strength in soils is instability slopes that finally cause sliding. In this study, following series of chemical, physical and strength tests, the effect of leaching has been appointed and investigated on the north Iran's clay soils. This study indicates that as a result of leaching the soil structure have become porous and removal the soluble salts and part of the fine particle change the dry unit weight, void ratio, specific gravity and hydraulic conductivity. Also, leaching cause the reduction of mechanical properties and unconfined compressive strength, Elasticity of modulus, Cohesion and friction angle in two condition as drained and undrained conditions. Finally, using the result of laboratory tests and comparison with the results of a case study using a numerical approach, the effect of leaching in sliding has been investigated.

Leaching, Soil, Modulus of Elasticity, Stability, Foundation