Investigation of the Effect of Adding Soft Sand and Lime on Strength Properties of Clay Soils

Due to the importance of using clay soil in many constructive projects such as, road foundation, irrigation canals and related hydraulic structures and etc., improvement of the physical and mechanical soil properties has been the main interest of the geo-technique specialists for years. In this regard different methods such as mixing clay soil with lime or cement have been used. It has been found that adding some other materials such as polymeric material and sand can more improve the properties of clay-lime mixture. In this research the effect of adding soft sand on the clay-lime properties has been investigated. The soil sample was mixed with 0%, 3%, 5%, 7%, and 9% of lime and 0%, 5%, 10% and 15% of soft sand, and totally a number of 20 samples were provided. The samples after maintaining under three periods including, 7, 14 and 28 days, saturation conditions and temperature of 25°C were tested with the unconfined compressive strength instrument. The main results of this research showed that adding only soft sand to the soil could not improve the soil properties, but using it with lime could significantly improve the soil geotechnical properties. It was found that the best mixture for the highest unconfined compressive strength and elasticity module is the a mixture of original soil with 7% and 10% of lime and soft sand respectively.