Aging effects on the mechanical property of waste mixture in coastal landfill sites

Coastal landfill sites not only offer an option for disposal but also create a new land space after the completion of landfilling. To perform proper design on settlement, stability, and/or bearing capacity at landfill sites, the geotechnical properties of the waste layer such as deformation and shear strength should be investigated. This research is focused on the mechanical properties of waste mixture sampled at a coastal landfill site including municipal solid waste incinerator ash, slag, soil and others, to provide useful information on geotechnical properties in utilizing coastal landfill sites after their closure. A series of triaxial consolidated undrained compression tests (CU) and hydraulic conductivity tests were carried out on the reconstituted waste samples before and after being cured in simulated leachate water in coastal landfill sites for different periods, to understand the aging effects on mechanical properties of waste mixture. It was shown that while curing results in an increase in the peak strength and deformation modulus, the residual strength was not affected by the curing periods. Scanning electron microscope observations and X-ray diffraction analysis on the waste samples after curing confirmed that the formation of ettringite and hydration products had a densification effect on the microstructure. The higher peak shear strength and lower hydraulic conductivity of the waste samples were attributed to this effect.