Improvement and stabilization of soft and loose fine-grained soils by microbially induced calcite precipitation method (Case study: fine-grained soil of Kermanshah University of Agriculture)

The process of biomineralization as a method of biological soil improvement refers to a set of biochemical reactions in which the sediment formed by bacteria causes the grains of soil to graft and thus improve its properties. In the present study, after optimizing the precipitation conditions, the effect of the sample making method on the biological improvement of Kermanshah clay fine-grained soil with two bacteria Bacillus megaterium and Lysinibacillus boronitolerans was studied. The results show that the method of sample making (in terms of adding biocementation solutions) has a significant effect on the improvement of compressive strength of samples. The maximum improvement of soil compressive strength (up to 2.68) occurred for Bacillus megaterium in adsorption method. In general, the addition of solution to the soil by adsorption method has been more effective in the proper placement of sediment between soil grains than the mixing and injection method. It has been more effective and in fact the solutions have been allowed to move between the soil grains to the corners where the grains join, thus resulting in the formation of effective sediment at the grains joint. Also, biological stabilization of the consolidation test sample reduced the soil void ratio change from 0.584 to 0.354 and the compression index from 0.077 to 0.038. The addition of biocementation solutions to the sample of atterberg limits test sample reduced the plasticity index from 26 to 19.