Effect of Compaction Effort on Penetration Resistance and Shear Strength of Landfilled and Fresh Municipal Solid Waste

High quality in-situ compaction of municipal solid waste (MSW) is required to ensure landfill stability. However given the heterogeneous composition of MSW, it is important to assess the potential sensitivity of Dynamic cone penetrometers (DCP) and direct shear apparatus to changes in compaction effort, composition and aging effect and different specific work per blow of DCP on penetration resistance (DPI) and shear strength parameters of fresh and excavated Johannesburg landfill municipal solid waste. The results reveal that for average density range of 354kg/m3 to 722kg/m3 the mobilized penetration resistance, DPI was 15–40 mm/blow for DCP specific work per blow of 144 kJ/m2 and 10– 33 mm/blow due to reduced work per blow of 92kJ/m2. The friction angle and cohesion of fresh waste and landfilled waste with fibrous content of 45% and 64% respectively are 19° and 12kPa for fresh waste and 21°and 31kPa for landfilled waste. 24 hours soaking of waste resulted in reduction in friction angle of fresh waste and cohesion of landfilled waste respectively. Controlling the ratio of sand, organics and fibrous content in recycling program is required to increase the stability of landfilled sites exposed to high tropical rainfall.