Bio-mediated soil improvement

[1] Methane gas hydrates, crystalline inclusion compounds formed from methane and water, are found in marine continental margin and permafrost sediments worldwide. This article reviews the current understanding of phenomena involved in gas hydrate formation and the physical properties of hydrate-bearing sediments. Formation phenomena include pore-scale habit, solubility, spatial variability, and host sediment aggregate properties. Physical properties include thermal properties, permeability, electrical conductivity and permittivity, small-strain elastic P and S wave velocities, shear strength, and volume changes resulting from hydrate dissociation. The magnitudes and interdependencies of these properties are critically important for predicting and quantifying macroscale responses of hydrate-bearing sediments to changes in mechanical, thermal, or chemical boundary conditions. These predictions are vital for mitigating borehole, local, and regional slope stability hazards; optimizing recovery techniques for extracting methane from hydrate-bearing sediments or sequestering carbon dioxide in gas hydrate; and evaluating the role of gas hydrate in the global carbon cycle.

/pdf/physical-properties-of-hydrate-bearing-sediments-3z1dw9zs82.pdf

Physical properties of hydrate-bearing sediments

The century-old Hazen formula for predicting the permeability of sand is based only on the D10 particle size. Whereas, the half-century-old Kozeny-Carman formula is based on the entire particle size distribution, the particle shape, and the void ratio. As a consequence, the Hazen formula is less accurate than the Kozeny-Carman formula. It is recommended that the former be retired and the latter be adopted.

Goodbye, Hazen; Hello, Kozeny-Carman

Staged construction uses controlled rates of load application to increase the foundation stability of structures founded on soft cohesive soils and to improve the slope stability of tailings dams. Because construction causes positive excess pore pressures and because actual failures usually occur without significant drainage, stability analyses should compute the factor of safety against an undrained failure as the most critical and realistic condition. This requires an undrained strength analysis (USA) that treats predicted or measured in situ effective stresses as equal to consolidation stresses in order to calculate variations in undrained shear strength during construction. The recommended USA methodology requires a detailed evaluation of changes in vertical stress history profiles, uses undrained strength ratios obtained from CK0U tests to account for anisotropy and progressive failure, and is more rational than stability evaluations based on UU and CIU triaxial compression testing. Conventional effe...

Stability Evaluation during Staged Construction

Aims: To gain an understanding of the environmental factors that affect the growth of the bacterium Sporosarcina pasteurii, the metabolism of the bacterium and the calcium carbonate precipitation induced by this bacterium to optimally implement the biological treatment process, microbial induced calcium carbonate precipitation (MICP), in situ.

Methods and Results:  Soil column and batch tests were used to assess the effect of likely subsurface environmental factors on the MICP treatment process. Microbial growth and mineral precipitation were evaluated in freshwater and seawater. Environmental conditions that may influence the ureolytic activity of the bacteria, such as ammonium concentration and oxygen availability, as well as the ureolytic activities of viable and lysed cells were assessed. Treatment formulation and injection rate, as well as soil particle characteristics are other factors that were evaluated for impact on uniform induction of cementation within the soils.

Conclusions:  The results of the study presented herein indicate that the biological treatment process is equally robust over a wide range of soil types, concentrations of ammonium chloride and salinities ranging from distilled water to full seawater; on the time scale of an hour, it is not diminished by the absence of oxygen or lysis of cells containing the urease enzyme.

Significance and Impact of Study:  This study advances the biological treatment process MICP towards field implementation by addressing key environmental hurdles faced with during the upscaling process.

Effects of environmental factors on microbial induced calcium carbonate precipitation

This manual presents data on soil behaviour, with emphasis on practical and empirical knowledge, required by geotechnical engineers for the design and construction of foundations and embankments It deals with: index and classification properties of soils; soil classification; clay minerals and soil structure; compaction; water in soils (capillarity, shrinkage, swelling, frost action, permeability, seepage, effective stress); consolidation and consolidation settlements; time rate of consolidation; the Mohr circle, failure theories, and stress paths; shear strength of sands and clays Four appendices deal with the following: application of the "SI" system of units to getechnical engineering; derivation of Laplace's equation; derivation and solution of Terzaghi's one-dimensional consolidation theory; pore pressure parameters (TRRL)

An Introduction to Geotechnical Engineering

Geosynthetic design and construction guidelines

This report summarizes the current state of the art and practice of prefabricated band shaped drains. Following an account of the theories of consolidation for vertical drains in soil, the two main sections explain the information needed about the ground and the drain,and how it is obtained for design. As well as understanding a clay deposit's macro fabric and stress history, it is necessary to assess its consolidation and permeability characteristics. Assessment methods based on laboratory and in situ testing and on the back analysis of trial embankments are explained. Drain characteristics are examined, and test results on commercial drains presented, with guidance on the selection of appropriate types. A final brief review identifies areas of band drain system design where knowledge is satisfactory or good, and those where further research is needed.

Prefabricated Vertical Drains: Design and Performance

Keywords: Drainage ; Consolidation Reference Record created on 2004-09-07, modified on 2016-08-08

Prefabricated Vertical Drains

This Manual was prepared as a textbook for the FHWA training course "Geotextile Engineering Workshop." The manual was prepared to enable the Highway Engineer to correctly evaluate each application and to properly select, design and construct with geotextiles in transportation applications of filtration, drainage, erosion control, materials separation, and soil reinforcement. The effectiveness of using geotextiles for each application is reviewed, particularly with respect to performance and cost when compared to alternate systems. Specifically covered are: Test methods for determining engineering properties of geotextiles; development of construction specifications; determination of fabric suitability and feasibility as cost effective alternative designs for specific applications; and construction procedures and details.

Robert D. Holtz

Papers

An Introduction to Geotechnical Engineering

Geosynthetic design and construction guidelines

Prefabricated Vertical Drains: Design and Performance

Prefabricated Vertical Drains

Geotextile engineering manual