Studies on the Efficiency of Compacted Cohesive Soil Liners for Landfills

Abstract

Since 1987 six test fields with different types of covering systems are being studied on the Georgswerder landfill in Hamburg. Besides combined systems with plastic liners on top of compacted cohesive soil liners, and an extended capillary barrier design, compacted cohesive soil liners without superjacent plastic liners are being tested. The measurements and experiments show that two years after installation the efficiency of the compacted soil liners is significantly reduced due to desiccation and shrinkage. Inspections of the liners show that a soil structure, already present at the time of installation, has become hydraulically effective during the dry summer of 1989. The measurements at the combined liner systems indicate that besides capillary rise of liquid water vaporous water movement too contributes to the desiccation. The results probably have consequences for the use of compacted cohesive soil liners without additional liners like covering plastic membranes or subjacent capillary barriers in general. In any case the structure of the liner material has to be destroyed, the individual lifts of the liner must mesh to avoid joints, and any formation of macropores and cracks has to be ruled out by technical measures.