Study of the mechanical compression behavior of municipal solid waste by temperature-controlled compression tests

Understanding the compression behavior of waste materials is important to the operation and rehabilitation of waste landfill sites. Nevertheless, predicting this behavior is extremely difficult because waste materials are heterogeneous and highly biodegradable. In terms of the mechanism, waste settlement comprises mechanical and biodegradation compressions. This research performs a series of tests to study the mechanical compression behavior of waste materials by using a specifically designed testing device. The device has the ability to keep the temperature low enough to impede the biodegradation of organics, thereby allowing the mechanical compression behavior to be determined. In general, the observed mechanical compression indicates that municipal solid waste (MSW) is very compressible. As the load increases, MSW becomes less compressible because the waste is getting denser. MSW also has a very large creep compression rate, whereby the coefficient of compression of the primary phase is only about 2–8 times that of the creep phase. The magnitude of loading and the elapsed time of loading affect the mechanical compression behavior of MSW. The effects of some parameters on the mechanical behavior are studied herein. MSW with higher dry density had a smaller compressibility. Higher water content also led to a higher compression rate in the primary and creep phases. The waste containing more compressible constituents compressed to a larger extent but with an insignificant increase in the compression rate. The biodegradation of organic constituents did not influence the mechanical compression behavior significantly but increased the rate of creep compression notably. This research also developed a regression relationship between the coefficient of volume compressibility and the dry density of the waste. The prediction of mechanical compression in a field case validated the application of this regression relationship.