Journal of Geotechnical and Geoenvironmental Engineering, Sep 1, 2002
Tests were conducted to determine the variation of water content and pore water suction for compa... more Tests were conducted to determine the variation of water content and pore water suction for compacted clayey soils. The soils had varying amounts of clay fraction with plasticities ranging from low to high plasticity. The unsaturated soil behavior was investigated for six conditions, covering a range of compactive efforts and water contents. The experimental data were fit to four commonly used models for the water content-pore water suction relationship. Each model provided a satisfactory fit to the experimental data. However, the individual parameters obtained from the curve fits varied significantly between models. The soil water characteristic curves �SWCCs� were more sensitive to changes in compaction effort than changes in compaction water content. At similar water contents, the pore water suction increased with increasing compaction effort for each compaction condition and soil type. For all compaction conditions, the lowest plasticity soils retained the smallest water content and the highest plasticity soils retained the highest water content at a specified suction. In addition, SWCCs for soils compacted in the laboratory and in the field were similar.
A study was conducted to determine the dynamic properties of compacted clayey soils subjected to ... more A study was conducted to determine the dynamic properties of compacted clayey soils subjected to low amplitude vibration. A fast and simple ultrasonic pulse transmission method was used. Tests were conducted on three clayey soils with low to high plasticity compacted using standard and modified Proctor effort over a range of water contents. The samples were allowed to dry after compaction and P-wave velocity, S-wave velocity, Poisson's ratio, and shear modulus were determined. The effects of soil type, compaction conditions, and degree of saturation on the dynamic response of the soils were investigated. The elastic wave velocities and the dynamic shear modulus increased as the soil plasticity decreased. The velocities and the modulus increased and the Poisson's ratio decreased as the degree of saturation decreased due to drying. Generally, the velocities and moduli increased significantly at the early stages of drying with the changes becoming more gradual as drying progressed. Variations were high for soils compacted with low energy and high water content. The shear moduli of the soils were also estimated using a common empirical equation. Suction values obtained for the test soils in a different study were used as effective stresses in the estimation. The estimated shear mod-uli agreed well with the measured values.
The Federal Highway Administration (FHwA) method and frost-tube measurements are used in Wisconsi... more The Federal Highway Administration (FHwA) method and frost-tube measurements are used in Wisconsin to detennine the timing and duration of spring load restrictions. In both methods, depth of freeze or thaw is used to detennine when to apply load restrictions and to determine their duration. Average daily air temperatures are used in the FHwA method to predict the start and end of freeze and/or thaw. Frost tubes are used to directly determine depth of freeze and/or thaw. An analysis is conducted to compare these two methods using air-temperature data (for the FHwA method) and frost-tube data obtained in Wisconsin. The analysis shows that differences exist between predicted (FHwA method) and measured (frost tubes) freeze and thaw conditions. The FHwA method is early (unconservative) in predicting the start of freeze and late (unconservative) in predicting the start of thaw. However, the method is late (conservative) when used to predict the end of thaw. A case history is also presented to compare the two methods.
Influence of Waste Temperatures on Long-Term Landfill Performance: Coupled Numerical Modeling
Journal of Environmental Engineering, Mar 1, 2021
AbstractA coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term b... more AbstractA coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term behavior of municipal solid waste in landfills is presented. Three numerical simulations—a convention...
Observations of Field Condition of an Exposed Geosynthetic Liner System
Developments in geotechnical engineering, 2017
Preliminary field observations during the removal of a composite geosynthetic liner system that h... more Preliminary field observations during the removal of a composite geosynthetic liner system that had been exposed for more than a decade are presented. The liner system was installed at a cell in a Subtitle D municipal solid waste landfill in San Luis Obispo, California (USA). The liner system consisted of (from top to bottom) a 1.5 mm-thick black HDPE geomembrane, a needle-punched geosynthetic clay liner (GCL), and a compacted subgrade. The liner system was not covered at any time since construction. The sides of the cell were relatively steep at 2H:1V slopes. Initially, the geomembrane was removed followed by removal of the geosynthetic clay liner. The geosynthetic clay liner panels were observed to be separated at multiple locations with gaps up to 220 mm wide and up to approximately 17 m long. The GCL also was relatively dry with granular consistency. In addition, a significant amount of bentonite that migrated from the GCL had accumulated between the GCL and the geomembrane at the toe of the slope.
Observations of Field Condition of an Exposed Geosynthetic Liner System
Preliminary field observations during the removal of a composite geosynthetic liner system that h... more Preliminary field observations during the removal of a composite geosynthetic liner system that had been exposed for more than a decade are presented. The liner system was installed at a cell in a Subtitle D municipal solid waste landfill in San Luis Obispo, California (USA). The liner system consisted of (from top to bottom) a 1.5 mm-thick black HDPE geomembrane, a needle-punched geosynthetic clay liner (GCL), and a compacted subgrade. The liner system was not covered at any time since construction. The sides of the cell were relatively steep at 2H:1V slopes. Initially, the geomembrane was removed followed by removal of the geosynthetic clay liner. The geosynthetic clay liner panels were observed to be separated at multiple locations with gaps up to 220 mm wide and up to approximately 17 m long. The GCL also was relatively dry with granular consistency. In addition, a significant amount of bentonite that migrated from the GCL had accumulated between the GCL and the geomembrane at t...
Influence of Waste Temperatures on Long-Term Landfill Performance: Coupled Numerical Modeling
Journal of Environmental Engineering, 2021
AbstractA coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term b... more AbstractA coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term behavior of municipal solid waste in landfills is presented. Three numerical simulations—a convention...
Heat is a primary byproduct of landfilling of municipal solid waste. Long-term elevated temperatu... more Heat is a primary byproduct of landfilling of municipal solid waste. Long-term elevated temperatures have been reported for MSW landfills under different operational conditions and climatic regions around the world. A conceptual framework is presented for management of the heat generated in MSW landfills. Three main strategies are outlined: extraction, regulation, and supplementation. Heat extraction allows for beneficial use of the excess landfill heat as an alternative energy source. Two approaches are provided for the extraction strategy: extracting all of the excess heat above baseline equilibrium conditions in a landfill and extracting only a part of the excess heat above equilibrium conditions to obtain target optimum waste temperatures for maximum gas generation. Heat regulation allows for controlling the waste temperatures to achieve uniform distribution at target levels at a landfill facility. Two approaches are provided for the regulation strategy: redistributing the excess heat across a landfill to obtain uniform target optimum waste temperatures for maximum gas generation and redistributing the excess heat across a landfill to obtain specific target temperatures. Heat supplementation
A comprehensive review of heat generation in various types of wastes and of the thermal regime of... more A comprehensive review of heat generation in various types of wastes and of the thermal regime of waste containment facilities is provided in this paper. Municipal solid waste (MSW), MSW incineration ash, and mining wastes were included in the analysis. Spatial and temporal variations of waste temperatures, thermal gradients, thermal properties of wastes, average temperature differentials, and heat generation values are provided. Heat generation was influenced by climatic conditions, mean annual earth temperatures, waste temperatures at the time of placement, cover conditions, and inherent heat generation potential of the specific wastes. Time to onset of heat generation varied between months and years, whereas timelines for overall duration of heat generation varied between years and decades. For MSW, measured waste temperatures were as high as 60 to 90C and as low as-6C. MSW incinerator ash temperatures varied between 5 and 87C. Mining waste temperatures were in the range of-27 to 65C. In the wastes analyzed, upward heat flow towards the surface was more prominent than downward heat flow towards the subsurface. Shallow zone thermal gradients generally ranged from 1 to 16C/m and deep zone thermal gradients ranged from-13 to 0C/m. Based on thermal
Journal of Geotechnical and Geoenvironmental Engineering, Nov 1, 2005
This study was conducted to investigate thermal aspects of municipal solid waste landfills as a f... more This study was conducted to investigate thermal aspects of municipal solid waste landfills as a function of operational conditions and climatic region. Spatial and temporal distributions of waste temperatures were determined at four landfills located in North America �Michigan, New Mexico, Alaska, and British Columbia�. Temperatures of wastes at shallow depths �extending to 6 to 8 m depth� and near the edges of a cell �within approximately 20 m� conformed to seasonal temperature variations, whereas steady elevated temperatures �23 to 57°C� with respect to air and ground temperatures were reached at depth and at central locations. Waste temperatures decreased from the elevated levels near the base of landfills, yet remained higher than ground temperatures. Thermal gradients in the range of approximately −30 to +22°C / m with average absolute values typically less than 5°C / m were measured within the wastes. Heat content �HC� of wastes was determined as the difference between measured waste mass temperatures and unheated baseline waste temperatures at equivalent depths. Peak HC values ranged from 12.5 to 47.8°C day/ day. The peak HCs were directly correlated with waste placement rates and initial waste temperatures, and they occurred at a specific average precipitation �2.3 mm/ day� beyond which further precipitation did not contribute to heat generation. HC was determined to conform to exponential growth and decay curve relationships as a function of climatic and operational conditions. Heat generation was determined based on HC using 1D heat transfer analysis. The heat generation values ranged from 23 to 77 MJ/ m 3 without losses and were significantly higher than biochemical prediction models, yet lower than values from incineration analyses. Overall, the highest values for temperatures, gradients, HC, and heat generation were observed in Michigan, followed by British Columbia, Alaska, and New Mexico. Integrated analysis of temperature and gas composition data indicated that temperature increases and HC values were greater during anaerobic decomposition than aerobic decomposition. Sustained high temperatures and heat generation occurred in wastes under anaerobic conditions.
Beneficial Reuse of Waste Insulation Material in Drilling Applications
This investigation was conducted to evaluate the beneficial reuse of post-consumer waste insulati... more This investigation was conducted to evaluate the beneficial reuse of post-consumer waste insulation materials in drilling and slurry applications. In particular, waste fibrous insulation was used to replace bentonite in slurry mixtures. Three civil engineering applications were considered for potential insulation waste reuse: drilled shaft/slurry trench construction, directional drilling, and vertical drilling. Effectiveness of slurries was assessed using conventional tests such as Marsh funnel viscosity, density, and filtrate loss. Filter cake thickness and filter cake permeability also were determined. Test results indicated that insulation materials could be used to replace up to 48% of bentonite in drilled shaft/slurry trench applications, up to 36% of bentonite in directional drilling applications, and up to 47% of bentonite in vertical drilling applications while maintaining acceptable engineering properties. Incorporation of waste insulation material in bentonite slurry mixtures is a viable beneficial reuse alternative.
Journal of Geotechnical and Geoenvironmental Engineering, Sep 1, 2002
Tests were conducted to determine the variation of water content and pore water suction for compa... more Tests were conducted to determine the variation of water content and pore water suction for compacted clayey soils. The soils had varying amounts of clay fraction with plasticities ranging from low to high plasticity. The unsaturated soil behavior was investigated for six conditions, covering a range of compactive efforts and water contents. The experimental data were fit to four commonly used models for the water content-pore water suction relationship. Each model provided a satisfactory fit to the experimental data. However, the individual parameters obtained from the curve fits varied significantly between models. The soil water characteristic curves �SWCCs� were more sensitive to changes in compaction effort than changes in compaction water content. At similar water contents, the pore water suction increased with increasing compaction effort for each compaction condition and soil type. For all compaction conditions, the lowest plasticity soils retained the smallest water content and the highest plasticity soils retained the highest water content at a specified suction. In addition, SWCCs for soils compacted in the laboratory and in the field were similar.
A study was conducted to determine the dynamic properties of compacted clayey soils subjected to ... more A study was conducted to determine the dynamic properties of compacted clayey soils subjected to low amplitude vibration. A fast and simple ultrasonic pulse transmission method was used. Tests were conducted on three clayey soils with low to high plasticity compacted using standard and modified Proctor effort over a range of water contents. The samples were allowed to dry after compaction and P-wave velocity, S-wave velocity, Poisson's ratio, and shear modulus were determined. The effects of soil type, compaction conditions, and degree of saturation on the dynamic response of the soils were investigated. The elastic wave velocities and the dynamic shear modulus increased as the soil plasticity decreased. The velocities and the modulus increased and the Poisson's ratio decreased as the degree of saturation decreased due to drying. Generally, the velocities and moduli increased significantly at the early stages of drying with the changes becoming more gradual as drying progressed. Variations were high for soils compacted with low energy and high water content. The shear moduli of the soils were also estimated using a common empirical equation. Suction values obtained for the test soils in a different study were used as effective stresses in the estimation. The estimated shear mod-uli agreed well with the measured values.
The Federal Highway Administration (FHwA) method and frost-tube measurements are used in Wisconsi... more The Federal Highway Administration (FHwA) method and frost-tube measurements are used in Wisconsin to detennine the timing and duration of spring load restrictions. In both methods, depth of freeze or thaw is used to detennine when to apply load restrictions and to determine their duration. Average daily air temperatures are used in the FHwA method to predict the start and end of freeze and/or thaw. Frost tubes are used to directly determine depth of freeze and/or thaw. An analysis is conducted to compare these two methods using air-temperature data (for the FHwA method) and frost-tube data obtained in Wisconsin. The analysis shows that differences exist between predicted (FHwA method) and measured (frost tubes) freeze and thaw conditions. The FHwA method is early (unconservative) in predicting the start of freeze and late (unconservative) in predicting the start of thaw. However, the method is late (conservative) when used to predict the end of thaw. A case history is also presented to compare the two methods.
Influence of Waste Temperatures on Long-Term Landfill Performance: Coupled Numerical Modeling
Journal of Environmental Engineering, Mar 1, 2021
AbstractA coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term b... more AbstractA coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term behavior of municipal solid waste in landfills is presented. Three numerical simulations—a convention...
Observations of Field Condition of an Exposed Geosynthetic Liner System
Developments in geotechnical engineering, 2017
Preliminary field observations during the removal of a composite geosynthetic liner system that h... more Preliminary field observations during the removal of a composite geosynthetic liner system that had been exposed for more than a decade are presented. The liner system was installed at a cell in a Subtitle D municipal solid waste landfill in San Luis Obispo, California (USA). The liner system consisted of (from top to bottom) a 1.5 mm-thick black HDPE geomembrane, a needle-punched geosynthetic clay liner (GCL), and a compacted subgrade. The liner system was not covered at any time since construction. The sides of the cell were relatively steep at 2H:1V slopes. Initially, the geomembrane was removed followed by removal of the geosynthetic clay liner. The geosynthetic clay liner panels were observed to be separated at multiple locations with gaps up to 220 mm wide and up to approximately 17 m long. The GCL also was relatively dry with granular consistency. In addition, a significant amount of bentonite that migrated from the GCL had accumulated between the GCL and the geomembrane at the toe of the slope.
Observations of Field Condition of an Exposed Geosynthetic Liner System
Preliminary field observations during the removal of a composite geosynthetic liner system that h... more Preliminary field observations during the removal of a composite geosynthetic liner system that had been exposed for more than a decade are presented. The liner system was installed at a cell in a Subtitle D municipal solid waste landfill in San Luis Obispo, California (USA). The liner system consisted of (from top to bottom) a 1.5 mm-thick black HDPE geomembrane, a needle-punched geosynthetic clay liner (GCL), and a compacted subgrade. The liner system was not covered at any time since construction. The sides of the cell were relatively steep at 2H:1V slopes. Initially, the geomembrane was removed followed by removal of the geosynthetic clay liner. The geosynthetic clay liner panels were observed to be separated at multiple locations with gaps up to 220 mm wide and up to approximately 17 m long. The GCL also was relatively dry with granular consistency. In addition, a significant amount of bentonite that migrated from the GCL had accumulated between the GCL and the geomembrane at t...
Influence of Waste Temperatures on Long-Term Landfill Performance: Coupled Numerical Modeling
Journal of Environmental Engineering, 2021
AbstractA coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term b... more AbstractA coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term behavior of municipal solid waste in landfills is presented. Three numerical simulations—a convention...
Heat is a primary byproduct of landfilling of municipal solid waste. Long-term elevated temperatu... more Heat is a primary byproduct of landfilling of municipal solid waste. Long-term elevated temperatures have been reported for MSW landfills under different operational conditions and climatic regions around the world. A conceptual framework is presented for management of the heat generated in MSW landfills. Three main strategies are outlined: extraction, regulation, and supplementation. Heat extraction allows for beneficial use of the excess landfill heat as an alternative energy source. Two approaches are provided for the extraction strategy: extracting all of the excess heat above baseline equilibrium conditions in a landfill and extracting only a part of the excess heat above equilibrium conditions to obtain target optimum waste temperatures for maximum gas generation. Heat regulation allows for controlling the waste temperatures to achieve uniform distribution at target levels at a landfill facility. Two approaches are provided for the regulation strategy: redistributing the excess heat across a landfill to obtain uniform target optimum waste temperatures for maximum gas generation and redistributing the excess heat across a landfill to obtain specific target temperatures. Heat supplementation
A comprehensive review of heat generation in various types of wastes and of the thermal regime of... more A comprehensive review of heat generation in various types of wastes and of the thermal regime of waste containment facilities is provided in this paper. Municipal solid waste (MSW), MSW incineration ash, and mining wastes were included in the analysis. Spatial and temporal variations of waste temperatures, thermal gradients, thermal properties of wastes, average temperature differentials, and heat generation values are provided. Heat generation was influenced by climatic conditions, mean annual earth temperatures, waste temperatures at the time of placement, cover conditions, and inherent heat generation potential of the specific wastes. Time to onset of heat generation varied between months and years, whereas timelines for overall duration of heat generation varied between years and decades. For MSW, measured waste temperatures were as high as 60 to 90C and as low as-6C. MSW incinerator ash temperatures varied between 5 and 87C. Mining waste temperatures were in the range of-27 to 65C. In the wastes analyzed, upward heat flow towards the surface was more prominent than downward heat flow towards the subsurface. Shallow zone thermal gradients generally ranged from 1 to 16C/m and deep zone thermal gradients ranged from-13 to 0C/m. Based on thermal
Journal of Geotechnical and Geoenvironmental Engineering, Nov 1, 2005
This study was conducted to investigate thermal aspects of municipal solid waste landfills as a f... more This study was conducted to investigate thermal aspects of municipal solid waste landfills as a function of operational conditions and climatic region. Spatial and temporal distributions of waste temperatures were determined at four landfills located in North America �Michigan, New Mexico, Alaska, and British Columbia�. Temperatures of wastes at shallow depths �extending to 6 to 8 m depth� and near the edges of a cell �within approximately 20 m� conformed to seasonal temperature variations, whereas steady elevated temperatures �23 to 57°C� with respect to air and ground temperatures were reached at depth and at central locations. Waste temperatures decreased from the elevated levels near the base of landfills, yet remained higher than ground temperatures. Thermal gradients in the range of approximately −30 to +22°C / m with average absolute values typically less than 5°C / m were measured within the wastes. Heat content �HC� of wastes was determined as the difference between measured waste mass temperatures and unheated baseline waste temperatures at equivalent depths. Peak HC values ranged from 12.5 to 47.8°C day/ day. The peak HCs were directly correlated with waste placement rates and initial waste temperatures, and they occurred at a specific average precipitation �2.3 mm/ day� beyond which further precipitation did not contribute to heat generation. HC was determined to conform to exponential growth and decay curve relationships as a function of climatic and operational conditions. Heat generation was determined based on HC using 1D heat transfer analysis. The heat generation values ranged from 23 to 77 MJ/ m 3 without losses and were significantly higher than biochemical prediction models, yet lower than values from incineration analyses. Overall, the highest values for temperatures, gradients, HC, and heat generation were observed in Michigan, followed by British Columbia, Alaska, and New Mexico. Integrated analysis of temperature and gas composition data indicated that temperature increases and HC values were greater during anaerobic decomposition than aerobic decomposition. Sustained high temperatures and heat generation occurred in wastes under anaerobic conditions.
Beneficial Reuse of Waste Insulation Material in Drilling Applications
This investigation was conducted to evaluate the beneficial reuse of post-consumer waste insulati... more This investigation was conducted to evaluate the beneficial reuse of post-consumer waste insulation materials in drilling and slurry applications. In particular, waste fibrous insulation was used to replace bentonite in slurry mixtures. Three civil engineering applications were considered for potential insulation waste reuse: drilled shaft/slurry trench construction, directional drilling, and vertical drilling. Effectiveness of slurries was assessed using conventional tests such as Marsh funnel viscosity, density, and filtrate loss. Filter cake thickness and filter cake permeability also were determined. Test results indicated that insulation materials could be used to replace up to 48% of bentonite in drilled shaft/slurry trench applications, up to 36% of bentonite in directional drilling applications, and up to 47% of bentonite in vertical drilling applications while maintaining acceptable engineering properties. Incorporation of waste insulation material in bentonite slurry mixtures is a viable beneficial reuse alternative.
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