Field Hydraulic Conductivity Tests for Compacted Soil Liners
Field hydraulic conductivity tests are required to determine the in situ hydraulic conductivity of compacted clay soils used in the liners for hazardous waste management facilities. The test must be capable of measuring hydraulic conductivities of 1 × 10-9 m/s or less, and the values obtained must be representative of the overall soil liner. Few of the methods available are capable of both measuring low hydraulic conductivities and obtaining representative values. Test methods which meet these requirements include large single-ring infiltrometers, sealed double-ring infiltrometers, and collection lysimeters. The main drawback in the use of collection lysimeters is that it can take months to obtain steady-state hydraulic conductivity values. Sealed double-ring infiltrometers are practical to use and have the advantage of few ambiguities in the experimental procedures, few possibilities for yielding false low values, and are large enough to yield results representing the overall liner characteristics.
Infiltrometers used on compacted soil liners should cover at least one elementary volume (REV) (e.g., at least 2 m2), and, in addition, at least three separate tests should be conducted to characterize spatial variability of the field hydraulic conductivity.