Determination of the Age of Municipal Solid Waste through Soil Tests

Evaluation of the geotechnical properties of Municipal Solid Waste (MSW) is troublesome due to heterogenic nature and the changes in such properties due to degradation with time. Previously abandoned dump yards in Sri Lanka are now being used for construction activities due to the shortage of lands in urban localities. However, the properties of such degraded MSW vary and the actual age of such MSW governs the properties. MSW samples of known age were collected from three dump sites, Kallundai in Jaffna, Karadiyana in Colombo and Matara, Sri Lanka. Particle size distribution, specific gravity, Atterberg limits, Proctor compaction, permeability and direct shear tests were conducted on ten samples in order to observe the variation of geotechnical properties with age. Gravel percentage (40% to 12%), liquid limit (61% to 17%), plastic limit (36% to 15%), plasticity index (24% to 1%), optimum moisture content (47% to 16%), hydraulic conductivity (1.8×10^-5 m/s to 1.3×10^-6 m/s) and organic content show decreasing trend with time, while sand percentage (55% to 78%), silt and clay percentage (4% to 20%), specific gravity (1.66 to 2.38), maximum dry density (933 kg/m³ to 1714 kg/m³) and waste homogeneity show increasing trend. Some data was collected from published literature to compare the results of the present study. This paper highlights the importance of the changes in the geotechnical properties of MSW with fill age when constructing on such grounds.