Design Method for Municipal Solid Waste Landfill Liner System Subjected to Sinkhole Cavity under Landfill Site

Abstract

Current design of municipal solid waste landfill liner systems utilizes granular and normally consolidated soil with geosynthetics materials to provide the required environmental and public health protection. Liner systems are required to isolate the waste from the natural subsoil and groundwater. The effect of land subsidence caused by sinkholes is an important design factor for municipal solid waste landfill liner systems. A high potential for sinkhole effects is evident in the central Florida area due to the geological conditions. Sinkhole occurrence under the landfill can cause ultimate failure of the liner system, thus allowing contamination of the natural subsoil and groundwater. The liner system becomes the sole base to bridge the cavity and withstand the overburden pressure. Failure of the liner system becomes a function of the geosynthetic yield strength and its maximum allowable deformation. In this study, the design of landfill liner system for implementation above sinkholes is based on soil arching the tension member theories. It is assumed that the natural subsurface soil deforms across a developing void thereby forming an arch. The design procedure accounts for the cumulative effects of soil types as single or multiple layers with geosynthetic materials. A series of charts are developed for various sizes of sinkhole cavity versus strength parameters of typical soils used in landfill liner systems design. Design examples of single layer and multiple layer liner systems are presented. Recommendations for future landfill design projects by government, industry, and geosynthetic manufactures are also made.