Centrifuge Modeling and Instrumentation of Geogrid-Reinforced Soil Barriers of Landfill Covers

Abstract

An experimental program was conducted to investigate the influence of geogrid as a reinforcement layer within the soil barrier of a landfill cover system under various levels of distortion. Centrifuge model tests were performed at 40 g on soil barriers subjected to continuous differential settlements using a 4.5 m radius beam centrifuge having a capacity of 2,500 g-kN available at IIT Bombay. Differential settlements were induced using a motor-based differential settlement simulator designed for a high gravity environment. Marker-based digital image analysis was adopted to estimate strain distribution along the geogrid layer and in the soil along the soil-geogrid interface at the onset of differential settlements. Various sensors, such as miniature pore pressure transducers, linear variable differential transformers, and strain gauges, were used to measure the water breakthrough, deformation profiles of the soil barrier, and the mobilized tensile load of model geogrids, respectively. Centrifuge model test results reveal that both 0.6 m and 1.2 m thick unreinforced soil barriers with an overburden pressure equivalent to that of a cover system experienced cracks extending up to the full thickness of the soil barrier and lost their integrity at low distortion levels. Soil barriers of 0.6 m and 1.2 m thickness with an overburden equivalent to that of landfill covers were reinforced with a suitable geogrid layer, and were found to sustain large distortions without any water breakthrough. An increase in the mobilization of the tensile load of the geogrid was noticed with an increase in the thickness of the soil barrier and overburden pressure equivalent to that of a cover system. This study also reveals the possibility of a reduction in the thickness of the soil barrier when it is reinforced with a suitable geogrid placed at one-fourth the thickness of the soil barrier from its top surface.