Use of Geogrids to Enhance Stability of Slope in Bioreactor Landfills: A Conceptual Method

In biroreactor landfills, biodegradation of municipal solid waste (MSW) is accelerated by leachate recirculation. However, the addition of moisture raises stability concerns. Reduced interlocking can also cause stability issues when MSW is shredded before disposing in bioreactor landfills. Engineers usually select safe slopes such as 3H:1V to design above ground MSW slopes in traditional dry landfills. But these slopes may not be safe for bioreactor landfills due to the stability concerns. Use of shallower slopes is not attractive because of the reduction in effective landfill capacity. This paper describes how geogrids may be used to enhance the stability of MSW slopes in bioreactor landfills. A preliminary stability analysis of un-reinforced and geogrid-reinforced MWS slopes was conducted using PLAXIS. The results indicated that the geogrids are capable of improving the factor of safety of MSW slopes. In geogrid-reinforced MSW failure surface developed at the ends of embedded geogrids separating reinforced MSW from un-reinforced MSW. This failure surface was larger than the failure surface developed for un-reinforced MSW. A different failure mechanism triggered when various lengths of geogrid were used. Although large displacements were found near the toe of the slope, a greater factor of safety was obtained.