HYDRAULIC CONDUCTIVITY OF 13 COMPACTED CLAYS

Hydraulic conductivity tests were conducted on thirteen compacted clay ey soils being used for compacted clay liners at landfills throughout the United States. The soils were prepared to various molding water co ntents and then compacted and permeated in the laboratory. Results of the tests show that for all of the soils, zones exist in the compactio n plane (i.e., dry unit weight vs. water content) where the hydraulic conductivity is similar. These zones fall roughly parallel to contours of constant initial saturation (degree of saturation at compaction), with lower hydraulic conductivities generally occurring for conditions corresponding to higher initial saturation. Wet of the line of optimu ms, lower hydraulic conductivity is also attained for soils that are m ore plastic and have a greater quantity of fines. A regression equatio n was developed from the data to estimate hydraulic conductivity given the initial saturation, compactive effort, plasticity index, and clay content.