Volume 32, Issue 6 (November 2004)
Mechanical Properties of Municipal Solid Waste
This paper deals with the compressibility and shear strength of Municipal Solid Waste (MSW) as measured in the laboratory. The waste studied was recovered from Bandeirantes Sanitary Landfill (São Paulo, Brazil) and is about 15 years old. More than 50 % by weight of MSW is organic paste and as much as 17 % is plastic and other strip materials. Consolidation and drained and undrained triaxial compression tests were performed in reconstituted waste specimens of large dimensions and with different unit weights considering both saturated specimens and specimens tested at natural moisture content. It is shown that the MSW exhibits a pronounced secondary compression; the influence of void ratio and stress on secondary compression index is discussed and compared with available data from MSW and soft soils. Typical stress-strain curves are presented and some peculiarities are shown, as the absence of failure even at large strains, up to 30 %, implies the need of deriving shear strength envelopes based on strain. The influence of saturation and of unit weight on shear strength is also addressed as well as the shear strength mobilization that shows that the friction tends to be fully mobilized at strains of about 20 %, while the cohesion intercept starts to be mobilized at strains of 10% and even more and a limiting value could not be observed in the strain range attained in the tests. The development of pore water pressures in the undrained tests and the variation of undrained shear strength with effective confining pressure are also addressed.