Bio-mediated soil improvement

In the past 25 years great strides have been made in the area of static stability and deformation analysis. The widespread availability of microcomputers has brought about considerable change in the computational aspects of slope stability analysis. Analyses can be done much more thoroughly, and, from the point of view of mechanics, more accurately than was possible without computers. Still, engineers performing slope stability analyses must have more than a computer program. They must have a thorough mastery of soil mechanics and soil strength, a solid understanding of the computer programs they use, and the ability and patience to test and judge the results of their analyses to avoid mistakes and misuse. Realistic analyses of deformations of slopes and embankments were not possible until about 25 years ago. They are possible now mainly because the finite-element method has been developed and adapted to these applications. The principal requirement for achieving reasonably accurate and useful results fro...

State of the Art: Limit Equilibrium and Finite-Element Analysis of Slopes

American Society of Civil Engineers

Ground-source or geothermal heat pumps are a highly efficient, renewable energy technology for space heating and cooling. This technology relies on the fact that, at depth, the Earth has a relatively constant temperature, warmer than the air in winter and cooler than the air in summer. A geothermal heat pump can transfer heat stored in the Earth into a building during the winter, and transfer heat out of the building during the summer. Special geologic conditions, such as hot springs, are not needed for successful application of geothermal heat pumps. Ground-source heat pumps (GSHPs) are receiving increasing interest because of their potential to reduce primary energy consumption and thus reduce emissions of greenhouse gases. The technology is well established in North America and parts of Europe, but is at the demonstration stage in the UK. This article provides a detailed literature-based review of ground-source heat pump technology, concentrating on loops, ground systems, and looks more briefly at applications and costs and benefits. It concludes with the prospects for GSHP in the UK. It is concluded that, despite potential environmental problems, geothermal heat pumps pose little if any serious environmental risk when best management practices are applied during the installation, operation, and decommissioning of these systems.

Ground-source heat pumps systems and applications

This lecture describes the latest findings with respect to the long-term performance of modern municipal solid waste (MSW) landfill barrier systems. Field data relating to the clogging of leachate collection systems and the latest techniques for predicting their performance are examined. It is indicated that the primary leachate collection systems may have service lives that range from less than a decade to more than a century, depending on the design details, waste characteristics and mode of operation. Recent data indicate that landfill liner temperatures can be expected to reach at least 30–40°C for normal landfill operations. With recirculation of leachate the liner temperature increases faster than under normal operating conditions, and may be expected to exceed 40°C. Temperatures (up to 40–60°C) may occur at the base of landfills where there is a significant leachate mound. Temperature is shown to have a significant impact on both contaminant migration and the service life of the liner system. Field...

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Long-term performance of contaminant barrier systems

This Paper describes a theoretical investigation into the behaviour of anchor plates in sand. Consideration is given to the effects of anchor embedment, friction angle, dilatancy, initial stress st...

The behaviour of anchor plates in sand

Basic concepts. Introduction. Overview of barrier systems. Transport mechanisms and governing equations. Complicating factors. Modeling the finite mass of contaminant. Modeling a thin permeable layer as a boundary condition. Hand solutions so some simple problems. Summary. Design considerations. Introduction. Impact assessment. Waste and leachate composition. Leachate mounding and collection. Leakage through liners. Leak detection systems. Landfill capping and the control of infiltration. Choic of barrier system and service life considerations. Geotechnical considerations. Summary. Clayey barriers: compaction, hydraulic conductivity and clay mineralogy. Introduction. Methods of assessing hydraulic conductivity. Compaction-permeability relationships. Clay mineralogy. Clay colloid chemistry. Clay-leachate compatibility by measurement of hydraulic conductivity. Introduction. Soil- MSW leachate compatibility. Compatibility of clays with liquid hydrocarbon permeants. Summary and conclusions. Flow modeling. Introduction. One-dimensional flow models. Analysis of two-and three-dimensional flow. Finite difference approximation. Application of the finite element method to the analysis of plane flow. Boundary element methods. Chemical transfer by diffusion. Introduction. Free solution diffusion (Do). Diffusion through soil. Steady-state diffusion. Transient diffusion. Use of laboratory and field profiles to measure diffusion coefficient De. Diffusion during hydraulic conductivity testing for clay - leachate compatibility. Summary and conclusions. Contaminant transport modeling.Introduction. Analytical solutions. Application of Laplace transforms to develop a finite layer solution for a single layer. Contaminant transport into a single layer considering a landfill of finite mass and an underlying aquifer. Finite layer analysis. Contaminant migration in a regularly fractured medium. Determination of diffusion and distribution coefficients. Introduction. Obtaining diffusion and partitioning/distribution coefficients: basic concepts. Example tests for obtaining diffusion and distribution coefficients for inorganic contaminants. Dispersion at low velocities in clayey soils. Effective porosity. Distribution coefficients and nonlinearity. Effect of leachate composition, interaction and temperature. Diffusion and sorption of organic contaminants. Use of field profiles to estimate diffusion coefficients. Summary and conclusions. Field studies of diffusion and hydraulic conductivity. Introduction. Examples of long-term field diffusion. Examples of short-term diffusion. Hydraulic conductivity of contaminated clay liners. Contaminant migration in intact porous media: analysis and design considerations. Introduction. Mass of contaminant, the ref erence height of leachate, Hr, and the equivalent height of leachate, Hf. Development of a contaminant plume. Effect of base velocity. Effect of horizonta

Clayey Barrier Systems for Waste Disposal Facilities

The undrained behaviour of anchor plates with a vertical or horizontal axis, resting in a saturated clay, is examined. Theoretical consideration is given to the effects of anchor embedment, layer d...

The behaviour of anchor plates in clay

A series of confined swell and hydraulic conductivity tests were conducted on a needle-punched geosynthetic clay liner (GCL) with water as the hydrating medium and reference permeant. Increases in the static confining stress and the needle-punching both restricted GCL swell and contributed to lower bulk GCL void ratios and hence significantly lower hydraulic conductivity values. A well defined linear-log relationship is found between the bulk void ratio and hydraulic conductivity. The number of pore volumes of permeant flow and consequently the level of chemical equilibrium is shown to have a significant effect on the hydraulic conductivity. It is shown that there is a decrease in hydraulic conductivity for small amounts of permeant flow for all ethanol/water mixtures examined. At or near chemical equilibrium, low concentration mixtures (25 and 50% ethanol) continued to produce relative decreases in GCL hydraulic conductivity due to the increased viscosity of the permeant; however, highly concentrated mixtures (75 and 100% ethanol) produced relative increases in GCL hydraulic conductivity arising from double layer contraction. The implications are discussed.

R. K. Rowe

Papers

Long-term performance of contaminant barrier systems

The behaviour of anchor plates in sand

Clayey Barrier Systems for Waste Disposal Facilities

The behaviour of anchor plates in clay

Selected Factors Influencing GCL Hydraulic Conductivity