Experimental Study on the Shear Strength and Durability of Microbial-Consolidated Silty Sand under Low pH Conditions

Addressing the issue of uneven distribution of calcium carbonate during soil solidification using Microbial Induced Calcite Precipitation (MICP) technology, an experimental study was conducted on the distribution of calcium carbonate in microbial-solidified soil samples using a low-pH single-phase grouting method. Through orthogonal experiments, the optimal culture conditions were determined as follows: pH = 3, O D ₆₀₀  = 4, and C S  = 2 mol/L. Based on this optimal grouting scheme, the distribution of calcium carbonate in microbial-solidified soil samples, as well as the changes in sample strength and durability, were investigated. Scanning Electron Microscopy (SEM) tests were also conducted to observe the microstructure characteristics of the solidified samples. The results indicate that the low-pH single-phase grouting method contributes to promoting a more uniform distribution of calcium carbonate during the microbial reaction process. Compared to the two-phase grouting method, the internal friction angle of samples solidified using the low-pH single-phase grouting method increased by 17.9%, and the cohesive force increased by 46.3%. In immersion tests, the final mass loss rate of samples solidified with the low-pH single-phase grouting method decreased by 16.13%, and the strength loss decreased by 21.1%. In dry-wet cycling tests, the final mass loss rate of samples solidified with the low-pH single-phase grouting method decreased by 13.8%, and the strength loss decreased by 16.9%.