MOISTURE FLOW IN MINERAL LANDFILL LINERS UNDER TEMPERATURE-GRADIENTS

In order to assess the risk of desiccation and cracking of the mineral bottom liner (without plastic liner) of a seven years old warm landfill, water contents were measured and soil hydraulic parameters determined in the lab. No cracks were visible, and a desiccation could not be proven due to the high spatial heterogeneity of the liner. Studies with a newly developed numerical model of coupled moisture and heat transport show that mineral liners might only crack if a plastic liner or very dry waste obstruct the temperature induced vapor transport from the waste to the mineral liner. Whether desiccation occurs under these conditions depends on the distance to groundwater and on the unsaturated hydraulic conductivity functions of the mineral liner and the subsurface. Simulations with unsaturated hydraulic conductivity functions that have been determined by different methods indicate that a new standard method to determine the unsaturated hydraulic conductivity of dense clayey substrates is necessary.