Estimating Field Hydraulic Conductivity of Compacted Clay

Results of hydraulic-conductivity tests conducted in the field and laboratory are presented for soils collected from 11 compacted-clay test pads or liners. The field tests were conducted with sealed double-ring infiltrometers to define the field-scale hydraulic conductivity ( K _F ). The laboratory tests were conducted using large undisturbed block specimens (diameter ≥ 0.3 m) and small specimens collected in thin-wall sampling tubes (diameter = 71 mm). Results of tests at low effective stress showed that the hydraulic conductivity of the block specimens was similar to K _F at each site. The hydraulic conductivities of block specimens from sites where K _F exceeded 10 ⁻⁹ m/s decreased by a factor of 4 when the effective stress was increased from 10 to 44 kPa. In contrast, the hydraulic conductivities of specimens from the other sites were reduced only by a factor of 1.5 under the same increment of effective stress.