• International Journal of Railway
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• v.6 no.3
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• pp.90-94
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• 2013

Cement or lime is generally used to improve the strength of soil. However, bacteria were utilized to produce cementation of loose soils in this study. The microo rganism called Bacillus, and $CaCl_2$ was introduced into loose sand and soft silt and $CaCO_3$ in the voids of soil particles were produced, leading to cementation of soil particles. In this study, loose sand and soft silt typically encountered in Korea were bio-treated with 3 types of bacteria concentration. The cementation (or calcite precipitation) in the soil particles induced by the high concentration bacteria treatment was investigated at 7 days after curing. Based on the results of Scanning Electron Microscope (SEM) tests and EDX analyses, high concentration bacteria treatment for loose sand was observed to produce noticeable amount of $CaCO_3$, implying a significant cementation of soil particles. It was observed that higher calcium carbonate depositions were observed in poorly graded distribution as compared to well graded distribution. In addition, effectiveness of biogrouting has also been found to be feasible by bio-treatment without any cementing agent.

• Journal of the Korean Geotechnical Society
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• v.29 no.2
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• pp.65-73
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• 2013

The purpose of this study is to confirm strength and effectiveness of grouting of the sand treated with bacteria. In order to analyze the cementation of sand treated with bacteria, five types of specimens(Not treated, Cement 2% treatment, Cement 4% treatment, Cement 2% + $CaCO_3$ 2% treatment and $CaCO_3$ 4% treatment) were made. Unconfined compressive strength tests were done on $D\;5cm{\times}H\;10cm$ specimens and biogrouting tests were performed on $D\;6cm{\times}H\;12cm$ specimens to observe the effectiveness of grouting with bacteria. As a result, Cement 2% + $CaCO_3$ 2% treatment was found to be the most effective in terms of the unconfined compressive strength.