Biodegradation-compression tests on municipal solid waste subjected to different vertical pressures

In order to investigate the long-term deformation properties of municipal solid waste (MSW) subjected to different vertical pressures, three biodegradation-compression test apparatuses for MSW are developed, whose functions include loading, temperature controlling, leachate recirculating, and gas collecting. Artificial waste samples filled in the test apparatuses are compressed under different conditions in the laboratory to simulate the settlement of MSW in landfills. The test results show that the primary settlement increases and the long-term settlement decreases respectively as the vertical pressure acting on the samples increases, and that the effect of pressure on the total settlement exhibits a decreasing trend with the increasing time. When the refuse is under appropriate decomposition condition, the settlement rate increases due to the enhancement of refuse decomposition, which results in significant settlement. Compressibility parameters are correlated with the state of decomposition. The strain-logarithmic time curves for the samples are approximately linear with a relatively flat slope at the early stage of compression, and at the last stage of compression, the strain-logarithmic time curves are also linear, but the logarithmic compression rate becomes large because of the added effects of decomposition.