European Union Risk Assessment Report

Analyses and experiments are performed to gain further insight into the behavior of unsaturated particulate materials, with emphasis on the pendular stage. First, interparticle forces are computed based on Laplace's equation; soil particles are ideally considered spherical or flat to facilitate the identification of the most relevant factors that affect unsaturated soil behavior. Second, the small strain stiffness is continuously measured on specimens subjected to drying, and changes in stiffness are related to changes in interparticle forces; data show important differences with previously published trends based on remolded specimens. Third, microscale experiments are performed to assess the strain at menisci failure in multiple deformation modes; results indicate that the lower the water content, the lower the strain required to eliminate the effects of capillarity, therefore, while capillary forces affect small strain stiffness, they may not contribute to large strain stiffness or strength. Finally, the rate of menisci regeneration is studied after a perturbation; stiffness recovery decreases with decreasing water content, and full recovery may not be reached when the degree of saturation is low. Several phenomena associated with the evolution of capillary forces during drying are identified.

Unsaturated particulate materials--particle-level studies

Engineering properties of municipal solid waste

The paper presents a study of the influence of grain-size distribution curve on the small strain shear modulus Gmax of quartz sand with subangular grain shape The results of 163 resonant column tests on 25 different grain-size distribution curves are presented It is demonstrated for a constant void ratio that while Gmax is not influenced by variations in the mean grain-size d50 in the investigated range, it significantly decreases with increasing coefficient of uniformity Cu = d60 / d10 of the grain-size distribution curve Well-known empirical formulas (eg, Hardin’s equation with its commonly used constants) may strongly overestimate the stiffness of well-graded soils Based on the RC test results, correlations of the constants of Hardin’s equation with Cu have been developed The predictions using Hardin’s equation and these correlations are in good accordance with the test data Correlations of the frequently used shear modulus coefficient K2,max with Cu and empirical equations formulated in terms 

Influence of the Grain-Size Distribution Curve of Quartz Sand on the Small Strain Shear Modulus Gmax

(NOTE: Each chapter concludes with Problems and References.) 1. Introduction. Need for Landfills. Principal Landfill Requirements. Landfill Components and Configuration. Landfill Envelope. Composite Liners. Benefits of Double Composite Liners. Liner Linkage Mechanisms. Scope and Organization of Book. 2. Landfill Siting and Site Investigation. Siting Considerations. Location Restrictions. Siting Process. Site Investigation. Borrow Source Investigation. Field Hydraulic Conductivity Tests. Material Laboratory Tests. 3. Compacted Clay Liners. Overview Compacted Clay Liners. Compaction and Permeability Considerations. Design of Compacted Clay Liners. Influence of Clods on Hydraulic Conductivity. Effect of Gravel Content on Hydraulic Conductivity. Effect of Freezing and Thawing on Hydraulic Conductivity. Summary Comments Regarding Compacted Clay Liners. 4. Geomembranes. Composition and Thickness of Geomembranes. Current Uses of Geomembranes in Landfills. Tensile Behavior of Geomembranes. Friction Behavior of Geomembranes. Tension Stresses Due to Unbalanced Friction Forces. Tension Stresses Due to Localized Subsidence. Runout and Anchor Trenches. Assessment of Leakage through Liners. Concluding Comments Regarding Geomembranes. 5. Geosynthetic Clay Liners. Types and Current Uses of Geosynthetic Clay Liners. Hydraulic Conductivity. Ability to Withstand Differential Settlement. Shear Strength. Differences between Geosynthetic Clay Liners and Compacted Clay Liners. Contaminant Transport through Geosynthetic Clay Liner and Compacted Clay Liner. Comparison of Mass Transport through a GCL and CCL. Recommendations for Use of Geosynthetic Clay Liners. Summarizing Comments Regarding Geosynthetic Clay Liners. 6. Engineering Properties of Municipal Solid Waste. Constituents of Municipal Solid Waste. Unit Weight of Municipal Solid Waste. Moisture Content of Municipal Solid Waste. Porosity of Municipal Solid Waste. Hydraulic Conductivity of Municipal Solid Waste. Field Capacity and Wilting Point of Municipal Solid Waste. Shear Strength of Municipal Solid Waste. Compressibility of Municipal Solid Waste. 7. Leachate Generation and Evaluation in MSW Landfills. MSW Leachate Characterization. Factors Affecting Leachate Quantity. Estimation of Leachate Production Rate in an Active Condition. Estimation of Leachate Production Rate in a Postclosure Condition. Hydrologic Evaluation of Landfill Performance (HELP) Model. 8. Liquid Drainage Layer. Profile of Leachate Drainage Layer. Soil Drainage and Filtration Layer. Geotextile Design for Filtration. Geonet Design for Leachate Drainage. Estimate of Maximum Liquid Head in a Drainage Layer. 9. Leachate Collection and Removal Systems. Subbase Grading. Leachate Collection Trenches. Selection of Leachate Collection Pipe. Deformation and Stability of Leachate Collection Pipe. Sump and Riser Pipes. Leachate Removal Pumps. 10. Gas Collection and Control Systems. Gas Generation. Gas Composition. Factors Affecting Gas Generation. Gas Generation Rate. Gas Migration. Types and Components of Gas Collection Systems. Gas Control and Treatment. Design of Gas Collection System. 11. Final Cover System. Components of Final Cover System. Alternative Landfill Cover. Field Study of Landfill Covers. Soil Erosion Control. Effects of Settlement and Subsidence. Differential Subsidence Case History. 12. Landfill Settlement. Mechanism of Solid Waste Settlement. Effect of Daily Cover. Landfill Settlement Rate. Estimation of Landfill Settlement. Effect of Waste Settlement on Landfill Capacity. Other Methods for Estimating Landfill Settlement. Estimation of Landfill Foundation Settlement. 13. Landfill Stability Analysis. Types of Landfill Failures. Factors Influencing Landfill Stability. Selection of Appropriate Properties. Veneer Slope Stability Analysis. Subsoil Foundation Failures. Waste Mass Failures. Concluding Remarks. 14. Vertical Landfill Expansions. Considerations Involved in Vertical Expansions. Liner Systems for Vertical Expansion. Settlement of Existing Landfill. Estimation of Differential Settlement Due to Waste Heterogeneity. Vertical Expansion over Unlined Landfills. Design Considerations for Landfill Structures. Geosynthetic Reinforcement Design for Vertical Expansions. Stability Analysis for Vertical Expansion. 15. Bioreactor Landfills. Introduction. Liquids Managements Strategies. Concepts of Waste Degradation. Leachate Recycling Methods. Bioreactor Landfill Issues and Concerns. Performance-to-Date. Summary Comments. 16. Construction of Compacted Clay Liners. Subgrade Preparation. Soil Materials for Compacted Soil Lines. Compaction Objectives and Choices. Initial Saturation Specifications. Clay Liner Compaction Considerations. Compaction Specifications. Leachate Collection Trench Construction. Protection of Compacted Soil. Field Measurement of Water Content and Dry Unit Weight. Construction Quality Assurance and Quality Control Issues. 17. Installation of Geosynthetic Materials. Material Delivery and Conformance Tests. Installation of Geomembranes. Installation of Geonets. Installation of Geotextiles. Installation of Geocompostes. Installation of Geosynthetic Clay Liners. 18. Postclosure Uses of MSW Landfills. Athletic and Recreational Facilities. Industrial Development. Aesthetics. Concluding Remarks. Appendix I. Help Model Input and Output-Active Condition. Appendix II. Help Model Input and Output-Postclosure Condition. Index.

Geotechnical Aspects of Landfill Design and Construction

The scope of this paper is to develop a new approach to the two-part wedge method for translational failure analysis of landfills. The upper and lower bound solutions for the landfill stability, i.e., FSmax and FSmin, can be readily determined using this method. Using an average factor of safety, FSave, to replace the true factor of safety, FStrue, the differences between FSave and FStrue are within 5% for most considered cases. The solutions from the new method ensure that the waste strength is not exceeded anywhere within the waste mass. The calculated results agreed well with the results computed from the computer code PCSTABL6. The ability of the new method to calculate the translational failure of waste mass with a predetermined sliding failure face is demonstrated. Also, a waste filling sequence to keep the factor of safety above a stipulated value during the operation phase of the landfilling process can be generated.

Translational failure analysis of landfills

This paper describes the results of an experimental investigation of capillary effects on the low strain shear modulus of sands in a partially saturated condition. It studies: (1) Void ratio; (2) c...

Voids and Granulometry: Effects on Shear Modulus of Unsaturated Sands

The scope of this paper is to develop a new analysis method introducing the effect of apparent cohesion of the waste and/or liner materials on the translational failure of landfills. The apparent c...

Effect of Apparent Cohesion on Translational Failure Analyses of Landfills

To properly design a drainage layer for either landfill leachate collection systems or final covers, the designer must be able to estimate the maximum liquid head over the barrier for any proposed configuration. This paper presents four explicit formulas for estimating the maximum liquid head over an impervious sloping barrier. By means of numeric comparisons, McEnroe's 1993 method is recommended for design of drainage layers for both bottom liners and final covers. Pipe slope is an important parameter that influences the maximum leachate head on the liner. Different combinations of base grade and pipe slope can directly affect the actual drainage behavior. If the pipe slope is steeper than the base grade, it will make a longer drainage distance and cause a high leachate head on the liner. A method for calculating the maximum liquid head in multilayered drainage media ~e.g., geosynthetic and soil! is presented in the paper. The key consideration for this case is to determine the equivalent hydraulic conductivity of the combined drainage media under the phreatic surface under unconfined seepage conditions.

Xuede Qian

Papers

Geotechnical Aspects of Landfill Design and Construction

Translational failure analysis of landfills

Voids and Granulometry: Effects on Shear Modulus of Unsaturated Sands

Effect of Apparent Cohesion on Translational Failure Analyses of Landfills

Estimation of Maximum Liquid Head over Landfill Barriers