Comparartive study of physical and index properties of clay- sand liners

Liners are constructed from naturally occurring earthen material. Soil Liners are needed to prevent the penetration of landfill leachate in to the soil. One of the requirements of modern sanitary landfill is that a soil liner be placed on the top of the existing soil, since it will minimize or eliminate water percolation. Of the different liner materials presently in use, the local availability of suitable clayey soils in many regions makes use of the soil liner as an economically attractive design alternative. Natural clay deposits when compacted can provide an effective hydraulic barrier in many situations such as environment and containment projects, waste disposal in landfill and earthen embankment and sometimes even used for disposal of hazardous wastes. Though the compacted clay liners possess advantages such as low permeability and large capacity of attenuation, they have high shrinkage and high expansive potential causing instability problem. To overcome that, some proportions of sand are added to the clayey soil. The main purpose of this work is to study the index properties such as atterberg limits, specific gravity, permeability and strength characteristics such as compressive strength, maximum dry density and shear strength parameters of CLAY- SAND LINERS. Also to reduce permeability, mineral admixture SILICA FUME is added to the clay-sand mixture. We used silica fume of proportions 15% and 25% by weight of clay-sand mixture and the test results show that the compacted clay-sand samples with 15% silica fume exhibit quite low permeability and significantly high compressive strength as compared to clay-sand samples.