Constant load and constant volume response of municipal solid waste in simple shear. (May 2017)

• Record Type: Journal Article
• Authors: Zekkos, Dimitrios; Fei, Xunchang
• Is Part Of: Waste management. Volume 63(2017)
• Page Start: 380
• Page End: 392
• Publication Date: 2017-05
• Subjects: Simple shear -- Shear strength -- Drained -- Undrained -- Municipal solid waste -- Landfills -- Stability; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2016.09.029
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: Simple shear testing of municipal solid waste in a unique 300-mm diameter device. Compare simple shear results under constant load and constant volume conditions. Evaluate two failure criterion and two friction angle interpretations. Shear resistance in constant volume is significantly lower than in constant load. Minimally compacted and "undrained" waste is representative in bioreactor landfills. Abstract: Constant load and constant volume simple shear testing was conducted on relatively fresh municipal solid waste (MSW) from two landfills in the United States, one in Michigan and a second in Texas, at respective natural moisture content below field capacity. The results were assessed in terms of two failure strain criteria, at 10% and 30% shear strain, and two interpretations of effective friction angle. Overall, friction angle obtained assuming that the failure plane is horizontal and at 10% shear strain resulted in a conservative estimation of shear strength of MSW. Comparisons between constant volume and constant load simple shear testing results indicated significant differences in the shear response of MSW with the shear resistance in constant volume being lower than the shear resistance in constant load. The majority of specimens were nearly uncompacted during specimen preparation to reproduce the state of MSW in bioreactor landfills or in uncontrolled waste dumps. The specimens had identical percentage of <20 mm material but the type of <20 mm material was different. The <20 mm fraction from Texas was finer and of high plasticity. MSW from Texas was overall weaker in both constant load and constant volume conditions compared to Michigan waste. The results of these tests suggest the possibility of significantly lower shear strength of MSW in bioreactor landfills where waste is placed with low compaction effort and constant volume, i.e., "undrained", conditions may occur. Compacted MSW specimens resulted in shear strength parameters that are higher than uncompacted specimens and closer to values reported in the literature. However, the normalized undrained shear strength in simple shear for uncompacted and compacted MSW was still higher than the normalized undrained shear strength reported in the literature for clayey and silty soils.