Prof. D. N. Singh

SNEHA J. KURIYAN

M.Tech.
Indian Institute of Technology Bombay, Powai, India sneha_kuriyan@yahoo.com

HYDRAULIC CONDUCTIVITY OF UNSATURATED SOILS: SOME LABORATORY INVESTIGATIONS

Contamination of ground water regime and subsurface soils is one of the major problems that has arisen due to rapid industrialization. In the recent years, this has led to an increasing concern for the environment especially in developed countries, and tackling this problem has become the central focus of much analyses. Spread of contaminants, in the unsaturated soil strata, mainly close to the ground surface and lying above the water table, depends on its hydraulic conductivity. Apart from this, knowledge of hydraulic conductivity is also critical while dealing with the design of earth structures such as soil covers, soil linings, earth dams, and other waste containment structures to determine the amount seepage through such structures under both saturated as well as unsaturated conditions. As such, estimation of unsaturated soil hydraulic conductivity becomes very important.
Most of the field as well as laboratory tests are extremely tedious and time consuming apart from being expensive. However, in the present study an attempt to indirectly estimate the hydraulic conductivity of unsaturated silty soil by conducting few preliminary experiments in the laboratory, to develop the SWCC?s (soil water characteristic curves) for the material. The potential of a geotechnical centrifuge for modeling various geoenvironmental engineering problems, being very well established, an effort has been made to obtain unsaturated state of a silty-soil, starting from its saturated state, by centrifugation. Tests have also been conducted using field and insertion tensiometers to develop the SWCC for the soil. Electrical resistivity experiments were also conducted on the soil in an attempt to correlate it to its hydraulic conductivity.
However, extensive experimentation and more refined testing methodology need to be adopted to determine unsaturated soil hydraulic conductivity with utmost accuracy.