Experimental evidence of anisotropy in municipal solid waste

Municipal SolidWaste (MSW) includes variable waste constituents that have significantly different physical and mechanical characteristics. Many of these constituents (e.g., paper, plastic, wood) are fibrous and provide a reinforcement effect. The properties of MSW vary not only with space, but also with time. Our understanding of the geotechnical properties of Municipal SolidWaste has improved significantly in the last two decades. Datasets of large-size laboratory and field experiments have become available shedding light on the complexities of Municipal SolidWaste behavior. The available data indicates that MSW is highly anisotropic. Two types of anisotropy are identified: Fabric anisotropy and stress-induced anisotropy. Observations and recent experimental evidence of the anisotropy of MSW in shear resistance, compressibility, wave propagation and hydraulic conductivity are presented. The influence of waste anisotropy on engineering practice remains unknown, but anisotropy should probably play a role in many aspects of landfill engineering practice. Currently, engineering practices do not consider the influence of anisotropy on the design and performance of MSW landfills with the exception, in some cases, of the anisotropy in hydraulic conductivity.