Optimization of Strength Factors in Microbial Solidification of Uranium Tailings Using Response Surface Methodology

Once the uranium tailings dam collapses, it will cause great harm to the surrounding ecological environment and people's safety. This study experimentally investigates microbial grouting reinforcement of uranium tailings to advance microbial reinforcement technology and facilitate its large-scale engineering applications. The study simulated original environmental conditions and used tap water to prepare the culture medium and cement without sterilization or pH adjustment. The response surface method was employed to optimize parameters affecting the immobilization of uranium tailings, and the results were verified. The mechanical strength of the immobilized uranium tailings was determined through unconfined compression tests, while their microstructures were analyzed using X-ray diffraction, scanning electron microscopy and computed tomography. The findings indicate that the response surface method optimizes test parameters accurately, with the concentration of the cementation solution and the grouting amount being two main factors influencing the compressive strength of the solidified uranium tailings. Without pH adjustment, sterilization, or slurry modification using tap water, the bacteria-cementation ratio was set at 1, the concentration of the cementation solution was 1.3 mol/L, and the grouting volume was 70 mL. Notably, the strength of the uranium tailings increased 27-fold after seven rounds of grouting compared to the water-only group, and 6-fold compared to the cementation solution-only group. This study contributes to reducing the complexity associated with the application of microbial grouting technology in soil stabilization and provides valuable references for other engineering practices.