LAUSR

The recycling and reuse of construction waste in landfill covers help reduce environmental pollution and promote sustainability. Further enhancement of the performance of the environmentally friendly landfill covers can be made by using vegetation as it is a low-cost, ecologically pleasant solution. Most related studies of vegetation were carried out in single-layer uniform soil while plant effects on water infiltration in layered soil such as a three-layer landfill cover system remain unclear. This keynote presents an integrated research approach combining laboratory one-dimensional tests as well as a 4-year full-scale field trial located in humid climates to explore the hydrological effects of plants on the performance of a novel three-layer landfill cover system using recycled concrete but without the installation of a geomembrane. Matric suction induced by plants was preserved to a greater extent under a novel vegetated three-layer landfill cover than under a bare cover even after an extreme rainfall event with a return period of greater than 1,000 years in humid regions like Hong Kong. During the 4-year field trial, the measured maximum annual percolation was 26 mm in the three-layer bare cover system, which was less than the US EPA-recommended 30 mm. Due to the presence of grass roots, the measured amount of annual percolation in the vegetated landfill cover was further reduced by up to 22%. Both the laboratory tests and field trial demonstrated that the vegetated three-layer landfill cover system using recycled concrete even without a geomembrane can effectively reduce percolation in humid climates.