The Potentials of Bacillus Amyloliquefaciens on improvement in the Geotechnical Characteristics of Poor Lateritic Soil

Abstract

Microbial Induced Calcite Precipitation (MICP) is a green technology which is being employed in the stabilization of poor soil.  Microorganisms that are capable of producing urea are introduced into the soil alongside chemical solution consisting of urea and calcium salt. This thus forms calcite within the soil matrix, thereby reducing permeability and increasing strength of the soil. In this study, a new urease producing Bacterium-Bacillus Amyloliquefaciens was locally isolated from a highly plastic lateritic soil characterized as A-2-4(7) soil and was used to treat the same soil. Engineering and biochemical tests were carried out on the treated soil specimen to assess the performance of the microbe. Unconfined compression strength (UCS) of the treated soil increased from 285.63 kPa to 335.13 kPa within 60 days curing age while the permeability (K) decreased from 6.10x10^-6cm/s to 4.36x10^-7cm/s within the same curing age. The calcite content has the peak precipitation on the sixtieth day with a value of 31.89g. Cation exchange capacity CEC of the treated soil specimen was found to be the highest on the day 60 of curing. SEM images of the treated samples show fully packed crystals structure of calcite clogging and cementing the soil particles. The regression statistical models for both UCS and K show that coefficients of determination (R²) for both models exceed 96%, indicating that the models capture the majority of the variability in the experimental dataset and remain consistently high, confirming that the five included predictors contribute meaningfully to each of the models without overfitting. Thus, use of MICP in lieu of conventional materials is recommended, being ecofriendly and effective in soil stabilization.