Considerations in the Design of Barrier Systems for Landfills and Lagoons
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A literature review of municipal solid waste landfill design was conducted to provide the knowledge base for development of an environmental decision support system (Landfill Advisor). Landfill Advisor integrates the current knowledge of barrier systems into a software program to assist in landfill design. The choices available for each liner component (e.g., drainage layer, geomembrane liner, compacted clay liner, geosynthetic clay liner) and their suitability for different situations (e.g., final cover, base liner, lagoon liner) are presented. Landfill Advisor covers both the design and related operational issues for municipal solid waste landfills, with consideration given to the interactions between components, operating conditions, and the natural environment with a view to maximization of long-term system performance. Unique to Landfill Advisor, the service life of each engineered component is estimated based on results from the latest research. Original research is also presented on the risk of geosynthetic clay liner (GCL) desiccation in low stress applications such as solar ponds. Numerical modelling was undertaken using a thermo-hydro-mechanical model with parameters that were developed and verified by comparison to previously reported laboratory data. A parametric study was performed to establish recommendations for future investigation. The water retention curve of the GCL was found to have a significant effect on the conditions that are expected to cause desiccation. The temperature coefficient of the water retention curve was also found to have a significant effect, yet this parameter is not well defined. Poisson’s ratio was found to affect the risk of desiccation in proportion to the applied stress. As reported by previous researchers, the initial degree of saturation of a GCL was found to be important to desiccation; however, the effect is diminished at low applied stress.