United States
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Increasingly stringent regulation of pollution and waste production worldwide drives the need to isolate contaminants that pose a threat to human and environmental health by using engineered barrier systems involving the use of low permeable materials. Over the past two decades, geosynthetic clay liners have gained widespread acceptance for use in such barrier systems. They are often used as a component of primary and secondary base liners or final cover systems in municipal solid-waste landfills as well as in regulated industrial storage and mining waste-disposal facilities.
Geosynthetic Clay Liners for Waste Containment Facilities gives a comprehensive and authoritative review of the current state of practice on geosynthetic clay liners in waste containments. It provides an insight into individual materials (bentonite and the associated geosynthetics) and the manufacturing processes. This is followed by the coverage of important topics such as hydraulic conductivity, chemical compatibility, contaminant transport, gas migration, shear strength and slope stability, and field performance.
1. Background and overview of geosynthetic clay liners
Introduction
Background
Bentonite
Geotextiles
Geomembranes
Other associated materials
GCL manufacturing
Current GCL products
Nonreinforced GCLs
Reinforced GCLs
Test methods and properties
Physical properties
Hydraulic properties
Mechanical properties
Endurance properties
Generic specification for GCLs
Equivalency issues
Summary
Acknowledgements
References
2. Durability and lifetime of the geotextile fibers of geosynthetic clay liners
Introduction and background
Structure and degradation of polymer fibers
Polymers used for GCL fiber reinforcement
Fiber configuration of GCL reinforcement
Oxidative effects on polymer structure
Tertiary carbon atoms
Crystallinity
Orientation
Antioxidants depletion mechanisms
Chemical reactions
Physical loss
Specific surface area
External environmental effects on oxidation
Energy level
Oxygen concentration
Liquid chemistry
Applied fiber stresses
Annealing
Durability evaluation and specification
Performance testing
Incubation methods for subsequent index testing
Index test methods and procedures
Geomembranes and geofilm
Summary and conclusions
Polymer structure, degradation and stabilization
Laboratory performance incubation and testing
Index testing with a suggested specification
Conclusion and recommendation
Acknowledgement
References
3. Mineralogy and engineering properties of Bentonite
Introduction
Mineralogy of smectite
Crystalline structure
Morphology and fabric
Layer charge
Exchangeable cations
Sodium activation of bentonites
Adsorption and swelling behavior
Short-range hydration mechanisms
Crystalline and osmotic swelling regimes
Crystalline swelling
Osmotic swelling
Engineering properties and their measurement
Mineralogical analysis
Cation exchange capacity
Surface area
Particle and granule size distribution
Water content
Swell index
pH, electrical conductivity and carbonate content
Fluid loss
Closing remarks
References
4. Hydraulic conductivity of geosynthetic clay liners
Geosynthetic clay liners in bottom liners and top covers
Definitions
Hydraulic conductivity
Unsaturated hydraulic conductivity
Permittivity
Intrinsic permeability
Hydraulic conductivity testing
Types of permeameters
Critical issues
Intact GCLs
Why do GCLs provide extremely low levels of hydraulic conductivity?
Hydraulic conductivity of different types of GCLs
Testing conditions
Overlapping GCLs and other special situations
Overlapping GCLs
Durability against environmental effects
Chemical compatibility
Clay-chemical and bentonite-chemical interactions
Consideration of the testing conditions
Effects of inorganic chemicals – concentration and valence of cations
Effects of waste leachates
Effect of the sequence of permeants
Modified bentonites
Acknowledgments
References
5. Contaminant transport through GCL-based liner systems
Introduction
Modeling contaminant transport through GCLs
Advection
Diffusion
Sorption
Establishing diffusion and sorption parameters for GCLs
Experimental procedures and data interpretation
Specified volume diffusion (SVD) test: Inorganic contaminants
Constant stress diffusion (CSD) apparatus: Inorganic contaminants
Volatile organic compound (VOC) diffusion testing
Factors influencing diffusion and sorption coefficients
Effect of eB on diffusion coefficient: Inorganic contaminants
Effect of type of GCL manufacture on inorganic diffusion coefficients
Different types of dissolved contaminants in contact with the GCL
Inorganic contaminants
Organic contaminants
Effect of temperature on volatile organic compound diffusion and
sorption coefficients
Constant stress vs specified volume diffusion testing
Summary of diffusion and sorption coefficients to use for preliminary designs
Contaminant migration assessments of GCL liner systems
Equivalency of GCL and CCL liner systems
Assessing GCL/CCL equivalency for municipal solid waste landfills: Example
Conclusions
References
6. Chemico-osmosis and solute transport through Geosynthetic clay liners
Introduction
Thermodynamics of irreversible processes
Experimental data
Physical interpretation of transport parameters
Role played by osmotic phenomena in contaminant transport through GCLs
Conclusions
References
7. Gas permeability of geosynthetic clay liners
Introduction
Background
Gas transport due to advection
Gas permeameter
Gas permeability
Effect of moisture content
Effect of hydration and desiccation
Effect of wet-dry cycles and ion exchange
Conclusions
8. Internal and interface shear strength of geosynthetic clay liners
Introduction
Materials
GCL reinforcement types
Geomembrane texturing types
GCL Shear strength testing equipment
Shear strength testing alternatives
Specimen size for the direct shear device
GCL specimen confinement for the direct shear device
Normal and shear load application for the direct shear device
Testing procedures
Moisture conditioning
Shearing procedures
GCL Internal shear strength
Shear stress-displacement behavior
Preliminary shear strength overview
Variables affecting GCL internal shear strength
Effect of normal stress
GCL Reinforcement
Moisture conditioning
Shear displacement rate
GCL internal shear strength variability
GCL-GM Interface shear strength
Shear stress-displacement behavior
Preliminary GCL-GM interface shear strength overview
Variables affecting GCL internal shear strength
Normal stress effects
Effects of GCL reinforcement type and GM polymer
Effect of GM texturing
Moisture conditioning
Shear displacement rate
GCL internal shear strength variability
Laboratory and field shear strength comparisons
Conclusions
References
9. Slope stability with geosynthetic clay liners
Introduction
Methods of analysis
Simplified wedge procedures
Possible failure surfaces
Representative cross-sections and three-dimensional geometries
Effective normal stresses
Displacement and strain compatibility
Seismic loads
Design criteria
Design shear strength for GCLs
Unconsolidated versus consolidated bentonite
Undrained versus drained shear
Peak versus residual shear strength
Internal versus interface shear strength
Summary of design shear strength
Approaches to mitigate stability problems
Flattening slope
Buttressing slope
Reinforcing slope
Reducing fluid pressures
Replacing weak shear surfaces
Reducing consequences of failure
Design examples
Example cover slope
Design check for base case
Design check for conservative and extreme cases
Example base liner slope
Design check for final closure geometry
Design check for interim waste filling geometry
Example liner construction
Conclusions
References
10. Hydrologic performance of final covers containing
Introduction
Covers relying solely on a GCL
Georgswerder study in Germany
Esch-Belval study in Luxembourg
Aurach study in Germany
Wisconsin study in USA
Covers with a GCL-composite barrier
Wisconsin study in USA
California study in USA
Oregon study in USA
Practical implications
Cation exchange and hydraulic conductivity
Promoting hydration and preventing dehydration
Conditions precluding cation exchange and increases in hydraulic conductivity
Recommended usage of GCLs in final covers
Acknowledgement
References
11. Oxygen diffusion through geosynthetic clay liners
Introduction
Background
Oxygen diffusion measurement
Oxygen diffusion coefficient
Concluding remarks
References
12. Field observations of GCL behaviour
Introduction
GCL performance in composite liner systems
Case histories of field performance
Physical integrity
Containment capability
Conclusions
References
