Location

Chicago, Illinois

Session Start Date

4-29-2013

Session End Date

5-4-2013

Abstract

Bioreactor landfills enhance municipal solid waste (MSW) degradation through recirculation of leachate inside the waste mass. In-situ monitoring of moisture distribution and changes in mechanical properties (stiffness) of MSW is needed to optimize the safe and effective operation of bioreactor landfills. Geophysical methods, such as electrical resistivity tomography, are shown to have great potential to monitor the moisture distribution. This study is aimed at investigating seismic surveys to characterize changes in dynamic properties (e.g., shear wave velocity and Poisson’s ratio) of MSW to infer the extent of degradation and provide the input needed for seismic stability evaluation. To achieve this goal, a seismic survey was performed in a bioreactor cell, within a MSW landfill (Orchard Hills Landfill, 15 km south of Rockford, Illinois, USA), to image seismic velocity structure and the Poisson’s ratio of MSW. Seismic data were collected through the cell using “fan shot” direct P- (compressional) and S- (shear) wave surveys. The fan shot surveys employed a sledgehammer source on one side of the landfill and geophones on the opposite side, thus exploiting the landfill’s topography and geometry to image MSW to a depth of at least 10 m. P- and S- wave velocity tomographic models from these direct-wave (through-pile) raypaths indicated a dramatic velocity increase below 5 m depth, perhaps indicating consolidation and compaction of MSW. Shear-wave velocity ranged from 150 m/s to 170 m/s. The P/S ratio ranged from 1.8 to 3.7, with an average of about 2.7 and Poisson ratios ranged from 0.29 to 0.46, with an average value of 0.42 (standard deviation 0.024). Below 4-5 m depth, compressional-wave seismic refraction profiling also indicates a subtle change in velocity. Repeated electromagnetic (EM) conductivity measurements with maximum sensitivity at 10 m depth show conductivity increased in the MSW approximately 20-40 mS/m over a 14 month period. Conditions appear to be more uniform at depth as well, after this 14-month interval. Overall, this study showed that seismic and EM surveys have potential to monitor spatial and temporal variation of dynamic properties of MSW and infer the extent of degradation.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Seventh Conference

Publisher

Missouri University of Science and Technology

Publication Date

4-29-2013

Document Version

Final Version

Rights

© 2013 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Apr 29th, 12:00 AM May 4th, 12:00 AM

Dynamic Properties of Municipal Solid Waste in a Bioreactor Cell at Orchard Hills Landfill, Illinois, USA

Chicago, Illinois

Bioreactor landfills enhance municipal solid waste (MSW) degradation through recirculation of leachate inside the waste mass. In-situ monitoring of moisture distribution and changes in mechanical properties (stiffness) of MSW is needed to optimize the safe and effective operation of bioreactor landfills. Geophysical methods, such as electrical resistivity tomography, are shown to have great potential to monitor the moisture distribution. This study is aimed at investigating seismic surveys to characterize changes in dynamic properties (e.g., shear wave velocity and Poisson’s ratio) of MSW to infer the extent of degradation and provide the input needed for seismic stability evaluation. To achieve this goal, a seismic survey was performed in a bioreactor cell, within a MSW landfill (Orchard Hills Landfill, 15 km south of Rockford, Illinois, USA), to image seismic velocity structure and the Poisson’s ratio of MSW. Seismic data were collected through the cell using “fan shot” direct P- (compressional) and S- (shear) wave surveys. The fan shot surveys employed a sledgehammer source on one side of the landfill and geophones on the opposite side, thus exploiting the landfill’s topography and geometry to image MSW to a depth of at least 10 m. P- and S- wave velocity tomographic models from these direct-wave (through-pile) raypaths indicated a dramatic velocity increase below 5 m depth, perhaps indicating consolidation and compaction of MSW. Shear-wave velocity ranged from 150 m/s to 170 m/s. The P/S ratio ranged from 1.8 to 3.7, with an average of about 2.7 and Poisson ratios ranged from 0.29 to 0.46, with an average value of 0.42 (standard deviation 0.024). Below 4-5 m depth, compressional-wave seismic refraction profiling also indicates a subtle change in velocity. Repeated electromagnetic (EM) conductivity measurements with maximum sensitivity at 10 m depth show conductivity increased in the MSW approximately 20-40 mS/m over a 14 month period. Conditions appear to be more uniform at depth as well, after this 14-month interval. Overall, this study showed that seismic and EM surveys have potential to monitor spatial and temporal variation of dynamic properties of MSW and infer the extent of degradation.