Effect of Microbially Induced Carbonate Precipitation (MICP) in the Highly Saline Silty Soil of the Cold Plateau Area of the Qinghai-Tibetan Plateau

Abstract

The discovery of new types of high-yield urease-producing microorganisms in extreme environments and the use of their particular functions to strengthen rock and soil materials has led to the study of microbially induced carbonate precipitation (MICP) in rock and soil materials. In this study, a new type of salt-tolerant and high-yield urease-producing microorganism was discovered in the highly saline environment in the Qaidam Basin in the cold and arid area of the Qinghai-Tibetan Plateau, and the salt tolerance of the microorganism and its basic MICP capability were tested and studied. The results show that the highest urease activity of this microorganism was maintained between 3.02 U and 5.03 U in a highly saline environment. The MICP test was carried out in highly saline and silty soil. Within a period of one week, the calcium carbonate content of the saline silty soil column increased by 8.11%, the porosity decreased by 6.12%, the pore size distribution decreased by 65–68%, the cohesion increased by 39.5%, and the internal friction angle increased by 4.3%. Under confining pressures of 100 kPa, 200 kPa, and 300 kPa, the shear strengths of the saline silty soil column increased by 22.1%, 13.5%, and 8.3%, respectively. The results of this study reveal that in a highly saline silty soil column, the new type of high-yield urease-producing microorganism discovered in the high-salinity environment in the cold and arid area of the Qinghai-Tibetan Plateau can produce vaterite and mineralized crystals and precipitates, which have a strengthening effect on saline silty soil particles, demonstrating the effectiveness and feasibility of MICP in a highly saline environment. This study provides a new approach for research on the strengthening of the saline soil foundation in the cold and arid area of the Qinghai-Tibetan Plateau.