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Paper sludges are being used with increasing frequency for construction of hydraulic barrier layers in landfill final covers because they often have substantial clay content and relatively low hydraulic conductivity. This paper addresses the assessment of the hydraulic conductivity of paper sludges using data obtained from a series of laboratory and field tests conducted on two barrier layers constructed with paper sludge that were part of final cover test sections. Field hydraulic conductivities were measured using sealed double-ring infiltrometers (SDRIs) and two-stage borehole permeameters (TSBs). Laboratory tests were conducted in flexible-wall permeameters on undisturbed specimens collected as blocks and in thin-wall sampling tubes as well as remolded specimens. The in-service hydraulic conductivity, computed from water balance data, was also available for comparison. Analysis of the data shows that similar hydraulic conductivities are measured in large field tests and on small laboratory specimens regardless of whether the specimens are undisturbed or remolded. Based on the analysis, recommendations are made regarding the need for field testing, laboratory and field test methods, and sampling techniques.
paper sludge, barrier layers, hydraulic conductivity, sealed double-ring infiltrometers, two-stage borehole permeameters, effective stress, sampling, gas
Associate Professor, University of Wisconsin Madison, Madison, WI
Geotech. Lab. Mgr., University of Wisconsin Madison, Madison, WI