Abstract
PurposeStabilization of weak soil can be achieved through different methods, some of which include jet column, cement stabilization and fly ash stabilization. Unfortunately, the use of the aforementioned methods of soil improvement affects the environment negatively thereby leading to environmental degradation. With the aforesaid impediment in mind, the need for devising methods of weak soil improvement becomes pertinent.MethodsBacillus sp. — a non-pathogenic organism found abundantly in soil — was investigated in this study as a potential agent of soil improvement. The usability of Bacillus sp. in soil improvement was investigated with direct shear tests and permeability tests under optimum conditions in this study.ResultTime-dependent study on the effect of the ureolytic bacteria Bacillus sp.-induced calcium carbonate precipitation shows reduction in permeability and increase in the strength of the soil under study. On exhaustion of the available nutrients in the soil, however, the strength of the soil is not negatively impacted.ConclusionMicrobially induced calcium precipitation by Bacillus sp. is effective in soil improvement as such it may serve as substitute for conventional soil stabilization techniques. The ability of the bacteria to precipitate calcium carbonate in the soil leads to reduction in the permeability and increase in the shear strength of the soil.
Highlights
Numerous studies have been conducted to assess the effect of microbially precipitated calcium carbonate on the permeability and strength of poor soils
Microbially induced calcium precipitation by Bacillus sp. is effective in soil improvement as such it may serve as substitute for conventional soil stabilization techniques
Studies relating to the effect of curing time on soil treated with Bacillus sp. and that on the changes in strength and permeability of the soil after the production of calcium carbonate by the bacteria are limited
Summary
Numerous studies have been conducted to assess the effect of microbially precipitated calcium carbonate on the permeability and strength of poor soils. Bacterial calcium carbonate precipitation has been utilized in the crack repair of granite and concrete (Gollapudi et al, 1995, Ramachandran et al 2001; Bang et al 2001; Ramakrishnan, 2007; Jonkers et al, 2009). These precipitations were found to fill pores, reduce permeability through the enhancement of particle bonding (Ivanov and Chu, 2008; Whiffin et al, 2007)
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