Settlement of Landfill Clay Cover Barriers with Geogrid Reinforcement

Abstract

Deformations in landfill clay cover barriers due to settlement in waste pills is a prevalent issue amassing to development of tensile cracks within the barrier, which reduces its usefulness and has a detrimental impact on its performance to reduce waste-water interaction. Geogrids have been widely used for reduction of differential settlement and preserve the utility and integrity of the barrier. However, these geogrids cannot mobilize maximum lateral resistance unless they are placed at optimum locations within the barrier. These locations need to be determined so as to obtain maximum possible benefit from the reinforcement. Hence, in this paper, laboratory-scale modeling of the landfill system has been carried out. Different landfill components such as the bottom liner, drainage layer, municipal solid waste pill, foundation layer/gas collection layer and the cover barrier have been scaled in accordance to the cover barrier height and a uniformly distributed load has been applied using a load frame. Filters, separators and protectors have been provided at suitable interfaces in the form of geotextiles throughout the landfill configuration. Kaolin clay and locally available sand blend in (4:1) proportion is used to simulate the bandwidth of clay cover material properties generally reported in the literature. Municipal waste was collected from different sources and mixed in proportion equivalent to the waste compositions of a typical Indian landfill. The waste was filled in five different horizontal phases, filled every two months and replaced with a new waste pill, which was prepared simultaneously in separate tanks, for different experimental program. Geogrids were applied in cover soil and different parameters such as initial layer spacing, vertical clearance between the reinforcement, effect of mechanical and physical properties of geogrids and the number of reinforcements have been analyzed in this study. The study showed the improvement in load-carrying capacity of the landfill cover with application of geogrids, subject to its optimum placement within the landfill cover. The mobilization of maximum tensile force in a geogrid occurred when the geogrid was placed at optimum positions.