Experimental study on reinforcement of calcareous sand by targeting activation of microbes producing urease

Six different targeted activation schemes for urea-producing microorganisms are designed for the biomineralization and reinforcement of calcareous sand. Through unconfined compression tests, calcium carbonate production measurements, SEM and XRD test analysis, the reinforcement effects of calcareous sand are evaluated, and the best targeted activation scheme is obtained. Finally, the changes of microbial community in the calcareous sand before and after activation are analyzed by high-throughput sequencing analysis results. The results show that: (1) the concentration of YE and NH₄Cl in the targeted activation plan will significantly affect the activation effects, among which the activation plan with 0.2g/L YE, 100 mmol/L NH₄Cl and initial pH value of 9.0 has the best effects. (2) The more calcite content and distribution of the calcareous sand is newly generated, the better the reinforcement effects of calcareous sand will be. Under the optimal activation scheme, the average UCS value of sand columns after mineralization reinforcement can be increased to 350 kPa. (3) The targeted activation changes the microbial community composition, making urea-producing microorganisms the dominant species.