Performance of earthen final covers of landfills in humid areas

The alternative earthen final covers (AEFCs) are constructed with relatively non-plastic soils with greater durability and lower cost and require relatively lower post-closure maintenance than conventional covers, so they are good choices for the final closure of landfills. A numerical model that can describe the interactions among earthen final cover, vegetation and atmosphere is developed based on the non-isothermal flow equation considering the thermal moisture coupling. It takes the meteorological condition, the evaporation from the ground surface and the transpiration of the vegetation into account. The performance of AEFCs in humid areas in China is investigated. The numerical results show that the capillary barrier cover can limit downward movement of water and the water is stored in the root zone layer. The capillary barrier cover performs better than the monolithic cover. The transpiration and the evaporation drain most of the water out of the cover and the evapotranspiration increases as the vegetation grows well. Capillary bairrier cover with 1.4 m in thickness and certain vegetation can prevent the deep percolation under the climatic condition considered in the study.