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ASSESSMENT OF DIFFERENT TREATMENT METHODS BY MICROBIAL-INDUCED CALCITE PRECIPITATION FOR CLAYEY SOIL IMPROVEMENT
Session: Problematic Soils and Ground Improvement II / Sols problématiques et amélioration du comportement II
Mohamed Shahin, Curtin University (Australia)
Liang Cheng, Curtin University (Australia)
Microbial-induced calcite precipitation (MICP) utilises the metabolic pathway of ureolytic bacteria to form calcium carbonate precipitation throughout the soil matrix, leading to increased soil strength and stiffness. MICP has proved to be an efficient technique for treatment of clean sand; however, there is lack of knowledge for MICP treatment of clayey soils. This paper assesses three different MICP methods including injection, premixing and diffusion, for treatment of clayey sand containing up to 20% clay content. The results indicate that the injection method is applicable only of treating sand columns that contain < 5% clay content. The premixing method, on the other hand, allowed a homogeneous placement of the bacteria cells in the sand columns and the subsequent injection of cementation solution under low pressure of 100 kPa enabled an adequate bio-cementation along specimens that contain up to 10% clay, resulting in up to 150% increase in the UCS values. The results also show that sand columns with 20% clay content can be treated using the diffusion method, leading to increased UCS values of up to 200% depending on the treatment duration. The overall conclusion is that bio-cementation of clayey soils is challenging and requires further investigation before field application.
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