Effects of Waste Placement Practices on the Engineering Response of Municipal Solid Waste

Abstract

Effects of Waste Placement Practices on the Engineering Response of MunicipalSolid Waste Jason T. Cox An extensive laboratory and field investigation was conducted at Santa Maria Regional Landfill (SMRL) in Santa Maria, California to determine the effects of waste placement practices on the engineering response of municipal solid waste (MSW). Laboratory and field testing was used to determine the engineering properties and monitor field response of MSW.The specific gravity (G s ) of manufactured MSW (MMSW), fresh MSW (FMSW), and old MSW (OMSW) was determined experimentally using a modified version of standard soil testing procedures. Effects of particle size, compactive effort, and degradation on the specific gravity of waste were evaluated. Specific gravity of manufactured waste samples increased with decreasing particle size, with compaction, and with increased degradation. The average specific gravity of uncompacted MMSW samples was 1.333, 1.374, and 1.424 for coarse, medium, and fine particle sizes, respectively. Specific gravity of coarse, medium, and fine MMSW samples compacted at dry of optimum ( = 30%) was determined to be 1.497, 1.521, and 1.552, respectively and at wet of optimum ( = 90%) to be 1.500, 1.542, and 1.570, respectively. The compacted and uncompacted specific gravity of fresh MSW was lower than manufactured and old MSW. The average G s of uncompacted and compacted fresh MSW was 1.072 and 1.208, respectively whereas old MSW had G s of 2.201.v Additional physical and engineering properties of MSW were determined for fresh and old wastes. A total of 8 magnetic extensometer settlement arrays and 4 thermocouple arrays were installed in old wastes. The settlement and temperature data were collected for an approximate duration of 1 year. In addition, laboratory experiments were conducted to determine the particle size distribution, organic content, and moisture content of fresh waste sampled from the active face of the landfill and from old waste sampled from different depths.The particle size distribution of OMSW was comparable to a well-graded coarsegrained soil. The average baseline moisture content of incoming MSW at SMRL was 42.7% (dry-weight basis). The average moisture content of residential MSW, commercial MSW, and self-delivered MSW were determined to be 57.7, 46.3, and 12.0%, respectively. The organic content of fresh and old MSW was determined to be 77.2 and 23.5%, respectively. Temperature increased over time due to heat generation of the waste mass. The temperature increased on average 3 to 6°C between the initial and final day of measurements for wastes that were 0.3 to 9 years old.Fresh and old wastes at SMRL exhibited unique compression behavior. A majority of the waste was undergoing secondary compression characterized using a secondary compression ratio ( ′ ) ranging from 0.013 to 0.067 with an average of 0.030. In addition, the fresh and old wastes exhibited recompression behavior. Fresh waste lifts were determined to be slightly overconsolidated such that the self-weig...

Implications of variable waste placement conditions for MSW landfills

“…Values of biochemical compression rate reported in literature were averaged to obtain a rate for optimum compaction conditions (0.215), whereas the high reported values were used for biochemical compression rate for wet of optimum conditions (0.36). Details of the analysis are presented in Cox (2013). Secondary settlement was calculated using Equation 8.…”