عنوان مقاله [English]
Engineered solid waste landfills are comprised of bottom barrier systems (leachate collection systems and compacted clayey liners) to prevent migration of the contaminants in the leachate from underneath the landfill. Clayey soils are widely used for construction of the landfill liners in engineered landfills. The compacted clayey liners should meet standard geotechnical specifications, such as soil index, strength, hydraulic, and contaminant transport parameters. If the compacted clayey soil cannot meet some of these specifications, it can be modified by means of additive material. The use of micro scale fine grained material, such as micro silica fume (MSF), has attracted the attention of engineers and researchers to modify the geotechnical characteristics of the clayey soils in geotechnical applications.The effect of micro silica fume additive on the improvement of the geotechnical properties of silty clay soil from the Nazloo region in Urumia City, Iran, was investigated. After determination of the geotechnical properties of the soil and MSF, the soil was mixed with 5 to 30 \% MSF by dry weight, and the geotechnical parameters of the mixed material were measured. The addition of 5 to 30 \% MSF to the soil caused the plasticity index and optimum water content to increase and the specific gravity and the maximum dry unit weight to decrease. The effect of MSF on soil hydraulic conductivity, shear and unconfined compression strength, and molecular diffusion coefficient, was investigated. The addition of MSF to the soil decreased hydraulic conductivity, improved strength properties, and increased cohesion. The addition of MSF to the soil caused the chloride diffusion coefficient to increase slightly, but the obtained values were in the range of the recommended values for clayey soils.
The overall conclusion of this investigation implies that the addition of maximum 30 \% by dry weight of micro silica fume to the Nazloo silty clay soil improves the geotechnical properties of the soil, so that it could be utilized in construction of the solid waste landfill liners in the region.