## 1 Introduction
[19; 20; 21], addressing the controversy over the effectiveness of system bolts in large-section loess tunnels, conducted field comparative tests and numerical simulation analysis, concluding that in large-section loess tunnels, system bolts have a limited control effect on tunnel surrounding rock deformation, and it is recommended to eliminate system bolts. These research findings have conducted beneficial studies on surface settlement, surrounding rock convergence deformation, surrounding rock seepage and moisture migration, mechanical response characteristics of support structures, and other aspects under the influence of different strata, excavation methods, and support measures in different regions, comprehensively reflecting the stability of regional tunnels to some extent and providing regional experience accumulation for tunnel design and construction [10; 22]. However, due to the combined influence of various complex factors, the stability of surrounding rock under specific conditions is the premise of safe construction and the primary goal for reasonably selecting excavation methods and support strategies. Therefore, it is necessary to timely assess the stability of surrounding rock during tunnel structural design, selection of excavation methods, and support strategies to determine the corresponding construction countermeasures. Currently, the evaluation of surrounding rock stability in loess tunnel design and construction mainly relies on expert experience and regional engineering analogy. Limited by the quantity of regional engineering experience accumulation, individual experience levels, and subjective judgments, there is significant variation and poor reliability in the results of surrounding rock stability evaluations. Therefore, there is an urgent need for an objective and scientific method to evaluate the dynamic stability of loess surrounding rock during construction [23]. Due to the fact that the stability of loess surrounding rock is influenced by multiple factors, such as geological conditions, soil strength parameters, tunnel depth, tunnel section, excavation methods, support measures and these factors are difficult to evaluate using quantitative indicators, mostly relying on qualitative descriptions, the stability state is ambiguous. Therefore, fuzzy mathematics methods can be used to classify the quality and stability of the surrounding rock [24; 25; 26]. The fuzzy mathematical model, as a systematic analysis method, is capable of fully considering and describing the influence of uncertain factors. It has been widely applied in various types of engineering and plays an important role in analyzing the impact of uncertain factors. To conduct a fuzzy evaluation of the stability state of the tunnel's surrounding rock, it is necessary to identify various factors affecting its stability, perform impact weight and consistency tests on these factors, analyze the degree of influence of each factor on the stability state of the surrounding rock, and then use a fuzzy comprehensive evaluation method to make judgments. This allows for guiding engineering construction and disaster management based on the evaluation indicators. In summary, research on the impact of water-rich loess tunnel surrounding rock stability has primarily focused on the geological characteristics of loess, the mechanism of water action, technical adjustments during construction, and corresponding engineering measures, achieving significant progress. However, extensive engineering practices indicate that the excavation of water-rich loess tunnels still faces numerous challenges. Some successful cases provide valuable experience, while failures serve as reminders that special attention must be paid to the stability of surrounding rocks during construction, adopting stricter and more scientific engineering measures. Continuous exploration and improvement are still necessary.