STUDY ON MECHANICAL PROPERTIES OF SOIL REINFORCED BY NOVEL UREASE PRODUCING BACTERIA IN SOUTH MOIST HOT AREAS

MICP technology cements loose soil particles into a stone body with a certain strength through the induced calcium carbonate. The morphology, size and crystal type of calcium carbonate would affect its filling and cementing effect in the soil, and then affect the mechanical properties of the cemented soil. On the basis of the related research about the reinforcement of the adverse soil mass by MICP technology, we screened the urease-producing bacteria from the soil in the southern moist heat areas for ultraviolet mutagenesis treatment. Then we selected the bacteria after UV mutagenesis, and got the mutant strain YB7 with high urease production. After that, we applied the mutant strain YB7 to the MICP laboratory grouting test of four soil samples. Combined with scanning electron microscope and energy spectrometer, we compared and analyzed the crystallization phenomenon of calcium carbonate in each sample. Finally, we carried out the direct shear test and uniaxial compression test on the grouting samples of the mutant strain YB7. Combining macroscopic mechanical characteristics and mesoscopic growth characteristics analysis of calcium carbonate, we studied the effect of the mutant strain YB7 on soil reinforcement systematically. The results showed that the novel urease producing bacteria in the southern warm wet area are feasible to reinforce the poor soil, but the structure of the soil can affect the formation of calcium carbonate. The formation effect of calcium carbonate in the soil with suitable particle gradation and suitable mineral morphology is better, and the cementation effect of the corresponding grouting sample is also better. The structure of the soil, the growth of calcium carbonate, and the cementation effect between the calcium carbonate and the soil particles can affect the mechanical properties of the sample. The results can provide a research basis for the further promotion and application of this technology.