Geotechnical properties of biocement treated sand and clay

The application of microbial technologies to improve the mechanical properties of soils is a new and fast developing research area in geotechnical engineering. Microbially induced calcium carbonate precipitation (MICP) is the most commonly employed biocementation method. Application of MICP for sand...

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Main Author: Li, Bing
Other Authors: Volodymyr Ivanov
Format: Theses and Dissertations
Language:English
Published: 2015
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Online Access:https://hdl.handle.net/10356/62560
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-625602023-03-03T19:22:01Z Geotechnical properties of biocement treated sand and clay Li, Bing Volodymyr Ivanov Andrew Whittle Chu Jian School of Civil and Environmental Engineering Singapore-MIT Alliance for Research and Technology DRNTU::Engineering::Civil engineering::Geotechnical The application of microbial technologies to improve the mechanical properties of soils is a new and fast developing research area in geotechnical engineering. Microbially induced calcium carbonate precipitation (MICP) is the most commonly employed biocementation method. Application of MICP for sand has been studied by many researchers. However, few studies had been carried out for fine-grained soils such as clay or other types of low permeability materials. In this research project, optimization of biocementation in sand and feasibility of using biocement to improve the mechanical properties of clayey soil were studied. Element tests using small cylindrical samples as well as model tests using soil of up to one cubic meter in volume were carried out. Different chemical compositions and types of bacteria were tested for both sand and clay. The properties of the MICP treated soil were assessed by unconfined compression tests, triaxial tests, direct simple shear tests, and flexible wall permeability tests using a triaxial cell. The results show that biocementation using urease producing bacteria (UPB) with low activity is effective for both small samples and relatively large samples in the model tests. Results of consolidated drained (CD) triaxial tests on sand with different degrees of biocementation treatment indicate that the strength gained through bio-treatment is related mainly to the increase in cohesion provided by the biocementation effect. In addition to increasing the shear strength, the permeability of sand is also reduced by bioclogging. One method is to form a calcite crust of 2 to 3 mm thick on the top surface of sand. This method can reduce the coefficient of permeability of sand from 10-4 m/s to 10-8 m/s. The possible applications of MICP to fine grained soils including kaolin, marine clay and bentonite were explored. The experiments show that a higher shear strength was observed for clayey soil mixed with UPB and cementation reagents compared to pure soil under the same water content. However, excess calcium cation used for the MICP process may impede the strength improvement. Another possible method is to make clay balls through premixing with bacteria and cementation reagents. Doctor of Philosophy (CEE) 2015-04-20T07:07:48Z 2015-04-20T07:07:48Z 2015 2015 Thesis Li, B. (2015). Geotechnical properties of biocement treated sand and clay. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/62560 10.32657/10356/62560 en 267 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Engineering::Civil engineering::Geotechnical
spellingShingle DRNTU::Engineering::Civil engineering::Geotechnical
Li, Bing
Geotechnical properties of biocement treated sand and clay
description The application of microbial technologies to improve the mechanical properties of soils is a new and fast developing research area in geotechnical engineering. Microbially induced calcium carbonate precipitation (MICP) is the most commonly employed biocementation method. Application of MICP for sand has been studied by many researchers. However, few studies had been carried out for fine-grained soils such as clay or other types of low permeability materials. In this research project, optimization of biocementation in sand and feasibility of using biocement to improve the mechanical properties of clayey soil were studied. Element tests using small cylindrical samples as well as model tests using soil of up to one cubic meter in volume were carried out. Different chemical compositions and types of bacteria were tested for both sand and clay. The properties of the MICP treated soil were assessed by unconfined compression tests, triaxial tests, direct simple shear tests, and flexible wall permeability tests using a triaxial cell. The results show that biocementation using urease producing bacteria (UPB) with low activity is effective for both small samples and relatively large samples in the model tests. Results of consolidated drained (CD) triaxial tests on sand with different degrees of biocementation treatment indicate that the strength gained through bio-treatment is related mainly to the increase in cohesion provided by the biocementation effect. In addition to increasing the shear strength, the permeability of sand is also reduced by bioclogging. One method is to form a calcite crust of 2 to 3 mm thick on the top surface of sand. This method can reduce the coefficient of permeability of sand from 10-4 m/s to 10-8 m/s. The possible applications of MICP to fine grained soils including kaolin, marine clay and bentonite were explored. The experiments show that a higher shear strength was observed for clayey soil mixed with UPB and cementation reagents compared to pure soil under the same water content. However, excess calcium cation used for the MICP process may impede the strength improvement. Another possible method is to make clay balls through premixing with bacteria and cementation reagents.
author2 Volodymyr Ivanov
author_facet Volodymyr Ivanov
Li, Bing
format Theses and Dissertations
author Li, Bing
author_sort Li, Bing
title Geotechnical properties of biocement treated sand and clay
title_short Geotechnical properties of biocement treated sand and clay
title_full Geotechnical properties of biocement treated sand and clay
title_fullStr Geotechnical properties of biocement treated sand and clay
title_full_unstemmed Geotechnical properties of biocement treated sand and clay
title_sort geotechnical properties of biocement treated sand and clay
publishDate 2015
url https://hdl.handle.net/10356/62560
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