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Bacteria, Biofilms, and Invertebrates: The Next Generation of Geotechnical Engineers?
The long-standing assumption in the geotechnical community that geotechnical systems are purely abiotic and free of biological influence has been misleading. In recent years this notion has been challenged by overwhelming evidence that biological processes occurring at microscopic scales can influence macroscopic geotechnical properties, even in environments as controlled as man-made fill materials. Biological organisms are pervasive throughout soils, existing at high densities (at least relative to humans) at nearly all length scales. One gram of typical top soil may be home to 1012 bacteria, and more than 106 bacteria may be present in a single gram of poorly graded engineered granular fill. Larger biological organisms, such as burrowing invertebrates (i.e., worms) can also exist at relatively high densities simultaneously, altering geotechnical properties as they break down large organic compounds for utilization by bacteria and fungi. These biogeochemical and biochemomechanical processes occur in unison as these organisms strive to live in soil ecosystems. While these organisms may not be purposeful geotechnical engineers, their biological activities alter the engineering properties of soils—stiffness, strength, permeability—that are used for geotechnical design. In recent years an increased awareness of the biological aspects of soils has been a focal point for research, with particular interest in harnessing these natural biological processes for geotechnical engineering benefit. Herein three processes in particular, which range in bio-geo-chem-mechanical processes, length scale, and research maturity are investigated. First, the process of bio-calcification through microbial ureolysis is examined, with linkages between bacterial activity, chemical composition, crystalline structure (SEM), geophysical signatures (VS), and engineering parameters such as strength and permeability are presented. Second, the process of slime-forming bacteria though aerobic metabolic processes is explored to form a temporary, jello-like slime that can reduce permeability and dynamic pore pressure generation. Third, the digestion and excretion of fecal pellets from marine-burrowing invertebrates is presented, showing a link between pellet structure, burrowing geometry, inter- and intrasoil porosity, and strength.
Bacteria, Biofilms, and Invertebrates: The Next Generation of Geotechnical Engineers?
The long-standing assumption in the geotechnical community that geotechnical systems are purely abiotic and free of biological influence has been misleading. In recent years this notion has been challenged by overwhelming evidence that biological processes occurring at microscopic scales can influence macroscopic geotechnical properties, even in environments as controlled as man-made fill materials. Biological organisms are pervasive throughout soils, existing at high densities (at least relative to humans) at nearly all length scales. One gram of typical top soil may be home to 1012 bacteria, and more than 106 bacteria may be present in a single gram of poorly graded engineered granular fill. Larger biological organisms, such as burrowing invertebrates (i.e., worms) can also exist at relatively high densities simultaneously, altering geotechnical properties as they break down large organic compounds for utilization by bacteria and fungi. These biogeochemical and biochemomechanical processes occur in unison as these organisms strive to live in soil ecosystems. While these organisms may not be purposeful geotechnical engineers, their biological activities alter the engineering properties of soils—stiffness, strength, permeability—that are used for geotechnical design. In recent years an increased awareness of the biological aspects of soils has been a focal point for research, with particular interest in harnessing these natural biological processes for geotechnical engineering benefit. Herein three processes in particular, which range in bio-geo-chem-mechanical processes, length scale, and research maturity are investigated. First, the process of bio-calcification through microbial ureolysis is examined, with linkages between bacterial activity, chemical composition, crystalline structure (SEM), geophysical signatures (VS), and engineering parameters such as strength and permeability are presented. Second, the process of slime-forming bacteria though aerobic metabolic processes is explored to form a temporary, jello-like slime that can reduce permeability and dynamic pore pressure generation. Third, the digestion and excretion of fecal pellets from marine-burrowing invertebrates is presented, showing a link between pellet structure, burrowing geometry, inter- and intrasoil porosity, and strength.
Bacteria, Biofilms, and Invertebrates: The Next Generation of Geotechnical Engineers?
DeJong, Jason (author) / Proto, Clayton (author) / Kuo, Matthew (author) / Gomez, Michael (author)
Geo-Congress 2014 ; 2014 ; Atlanta, Georgia
Geo-Congress 2014 Technical Papers ; 3959-3968
2014-02-24
Conference paper
Electronic Resource
English
Bacteria, Bio-Films, and Invertebrates: The Next Generation of Geotechnical Engineers?
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