Cyclic Simple Shear Testing of Degraded Municipal Solid Waste from California Under Constant Volume and Constant Load Conditions

Abstract

For municipal solid waste (MSW) landfills that are situated in seismically active regions, the response of MSW under dynamic loading is critical to landfill design. In this study, a large-size simple shear device is utilized to perform cyclic testing on MSW under constant load (CL) and constant volume (CV) conditions which are considered equivalent to drained and undrained conditions respectively. The MSW sample was excavated from a California landfill located in a seismically active zone and was fully degraded in the laboratory in controlled conditions. Degraded MSW specimens were compacted and consolidated, and then sheared cyclically using cyclic stress ratios (CSR) of 0.1, 0.2, 0.3 and 0.4 sequentially. For a given number of cycles, higher CSR and higher vertical stress result in higher vertical strain and shear strain under CL conditions, and higher excess pore pressure ratio and shear strain under CV conditions. When subjected to cyclic loading, MSW is found to experience significant vertical strain under CL conditions (i.e., compression), or generate potentially significant pore pressures under CV conditions.