Compositional effects on the mechanical properties of municipal solid waste

This study investigated the effect of waste composition and initial sample unit weight on the consolidation and simple shear behavior of municipal solid waste (MSW) as a part of a National Science Foundation-funded collaborative research project among the University of California at Berkeley, the University of Texas at Austin, and Geosyntec Consultants. The objective of the project was to evaluate the influence of waste composition and stress system on the mechanical properties of MSW. The research conducted at Arizona State University (ASU) focused on the effect of particle size, as the ASU testing device could accommodate the largest particles. Reconstituted specimens with three different particle size distributions (composition ratios) were tested at ASU. To investigate the effect of initial unit weight on MSW behavior, tests were also performed on specimens with the same composition ratio but different initial unit weight.;The one-dimensional compression tests investigated the behavior of MSW in both loading and unloading/reloading. The coefficient of lateral earth pressure at-rest for MSW was also investigated in the one dimensional compression tests. In cyclic simple shear tests, the shear modulus and damping ratio of MSW were investigated. Monotonic loading conducted subsequent to cyclic loading was used to investigate the shear strength of MSW. The ASU test results indicate that initial unit weight is the most important factor affecting the consolidation behavior, small strain shear modulus, damping ratio, and static shear strength of MSW. Particle size does appear to affect modulus reduction, with the modulus degrading at a slower rate with respect to cyclic shear strain in specimens with a greater percentage of larger particles.