Evaluating the application of carbonate precipitation driven by bacterial activity for stabilizing saline and alkaline clays

摘要

Biocementation is a biochemical reaction that occurs in soil structures in which insoluble calcium carbonate forms in the soil pores and ultimately improves the soil stiffness and strength. The present study investigates this process by injecting and mixing Bacillus pasteurii into clay soils from the Meighan Desert of Iran, which contain specific salt and mineralogical compounds. Unconfined compressive strength tests were performed to evaluate the strength of the soils after being treated to a range of bacteria injection and mixing conditions. The plastic properties, pH, and electrical conductivity of the samples were measured to examine the soil changes after treatment. To address the specific regional and standard culture medium characteristics, two new culture media were prepared and tested according to the salt composition in the regional soil. Wind tunnel and flexural strength tests were also conducted to examine the sample changes after bacterial treatment. Scanning electron microscopy and X-ray diffraction analyses were applied to evaluate the microstructural changes in the samples. The method of mixing clay with bacteria was found to increase the clay sample strength by 78.5% after 28 days compared with the untreated sample. This environmentally friendly method can be used to increase soil strength and reduce wind erosion in geotechnical engineering projects.