Effect of microorganism on engineering properties of cohesive soils

This paper presents the study of the effect of microorganism Bacillus pasteurii on the properties such as Atterbergs' limit and unconfined compressive strength of cohesive soils. The results of this study reveal that the liquid limit and plasticity index for all clay soils decreased and the unconfined compressive strength increased. Decrease in plasticity index is very high for Kuttanad clay followed by bentonite and laterite. The unconfined compressive strength increased for all the soils. The increase was high for Kuttanad soil and low for laterite soil. After 24 h of treatment the improvement in the soil properties is comparatively less. Besides the specific bacteria selected Bacillus pasteurii, other microorganisms may also be taking part in calcite precipitation thereby causing soil cementation. But the naturally present microorganisms alone cannot work on the calcite precipitation.