Effect of Microbial Stabilization on High, Intermediate and Low Compressible Clay

Abstract

Engineers may have to construct structures on sites having expansive soil. By treating the soil with admixtures such as cement, bitumen, plastic, etc. Soil stabilization improves strength characteristics such as bearing capacity and unconfined compressive strength. The conventional approaches are time-intensive and are not economically viable. Through the utilization of the Microbial-Induced Calcite Precipitate technique (MICP), microbes have recently emerged to be known as a component that significantly improves the characteristics of soil. It is economical and environmentally friendly. They work on the soil to increase compaction by reducing water absorption and minimizing the void spaces between soil particles. The stabilization of soil takes place by the process of bio-cementation and bio-clogging. Calcite precipitated at the void spaces when the cementation reagent and bacterial solution were introduced to the clayey soil in various proportions. Improvements in density and strength of clayey soil are studied using Bacillus subtilis bacterium concentrations of 1 x 107 cells/ml, cementation reagent composed of urea and calcium chloride (0.5M, 1M, 1.5M, and 2M), and treatment intervals of (7, 14, and 28 days). An unconfined compressive strength test was used to evaluate the optimum bacterial solution concentration, cementing solution molarity, and treatment duration. Maximum strength improvement ratios among the three different expansive soils were also studied. SEM analysis is carried out for the optimum combinations in the three types of soil to confirm the presence of calcite. Hence, an attempt is made to research how bacteria affect the strength of high, intermediate, and low-compressible clay.