## 1 Introduction
Another study using a layered injection method for MICP biological solidification of tailings, combined with unconfined compressive strength, calcium carbonate content, and heavy metal leaching, optimized the solidification time of MICP biogel tailings, and improved strength and cost-effectiveness [17]. Although current research has yielded productive results in using MICP technology to reinforce, improve, and repair soil, most studies have used deionized or ultrapure water to prepare the required medium and grouting slurry. This approach aims to maximize the mineralization effect and prevent the growth of non-target bacteria during the cultivation and screening of mineralized microorganisms. After preparation, high-temperature autoclaving and filtration sterilization were performed, with microbial inoculation and expansion conducted on an aseptic operation table. However, in natural environments, microorganisms do not thrive in such pure conditions, especially in uranium tailing ponds. These environments are complex, often containing sources of radioactivity and heavy metals, which introduce various non-target bacteria and unstable pH values that hinder the growth of mineralized microorganisms. Additionally, in actual engineering grouting processes, the quantities of microorganisms, culture media, and cementation solutions are often thousands or even tens of thousands of times greater than those used in laboratory settings. Consequently, using deionized or ultrapure water to prepare such large volumes of bacterial solutions and slurries is impractical, and the sterilization process becomes extremely challenging. Owing to the interaction of these factors, the stepwise optimization in experimental design may miss the optimal combination of factors and is often associated with a significant experimental workload. MICP is a novel grouting and reinforcement method, and its microstructure has not been thoroughly studied. Additionally, there is a lack of guidance on design methods and concepts related to the influencing factors. This poses a challenge in proposing the optimal grouting parameters for the MICP method while accelerating its implementation in engineering practice. Response surface methodology (RSM) is a comprehensive experimental design and mathematical modeling optimization method that can obtain the optimal value of each factor by conducting experiments on representative local points to establish the functional relationship between the factors and the results on a global scale, and to study the influence of the interaction between multiple factors on the target response value [18]. In this study, according to the native environmental conditions, the slurry was no longer configured with deionized or ultrapure water, but the medium and cementation solution were configured with tap water, and the uranium tailings were reinforced by microbial grouting without sterilization or pH adjustment. The response surface method was used to optimize and verify the influencing factors of MICP-cured uranium tailings; the unconfined compression test was used to determine the mechanical strength of the solidified uranium tailings under the optimized parameters; and the microstructure was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and computed tomography (CT) methods. The results of this study help to reduce the operational difficulty and economic costs of MICP technology in uranium tailings reinforcement engineering. By applying response surface methodology to the determination of grouting parameters, we greatly facilitate the parameter identification process in grouting projects, which in turn aids in promoting the application of MICP technology in related geotechnical engineering practices.