Abstract
Recently, the concept of using biological process in soil improvement otherwise called bio-mediated soil improvement technique has shown greater prospects in the mitigation of liquefiable soils. It is an environmental friendly technique that has generated great interest to geotechnical engineers. This paper presents a review on the microorganism responsible for the biological processes in soil improvement system, factors that affect biological process, identifying the mechanism of liquefaction and commonly adopted method to mitigate liquefaction. Next, the effect of microbial induced calcite precipitation (MICP) on the strength and cyclic response were also analyzed, where it was identified that higher cementation level leads to formation of larger sized calcite crystals which in turn leads to the improved shear strength, stiffness and cyclic resistance ratio of the soil. However, the effects of various bacteria, cementation reagent concentrations amongst other factors were not fully explored in most of the studies. Finally, some of the challenges that lay ahead for the emerging technology are optimizing treatment factors (bacteria and cementation reagent concentration), upscaling process, training of researchers/technologist and long – time durability of the improved soils.
Highlights
Rapid urbanization and population growth in most developing countries has led to more demand for civil infrastructures, which are erected over limited available lands
This paper presents a review of the use of microbial induced calcite precipitation (MICP) as a mitigation technique for liquefiable soils
The results indicated that the rate of calcite formation increased with bacterial cell concentration, and the bacterial cell concentration had a greater influence on rate of calcite than initial urea concentration
Summary
Rapid urbanization and population growth in most developing countries has led to more demand for civil infrastructures, which are erected over limited available lands Some of these infrastructures are built in low lands, lakes, rivers, that are being filled to build such structures. If these occur, soil tends to act like liquid and the shear strength and stiffness of the soil are drastically reduced [1]. The most common soil improvement techniques include densification of the soil through mechanical energy, preloading to achieve consolidation, addition of chemical admixture and grouting with synthetic materials such as cement, epoxy, and sodium silicate [3]. Some research gaps are highlighted for future research and development
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