## 4 Summary of the Project and Preprocessing of Data
### The Selection of Risk Assessment Indices  
There are numerous factors that can impact tunnel construction, and the mechanism of influence for different factors is intricate. Based on an analysis of existing research findings, these factors can generally be categorized as natural and geological factors. Given the complex characteristics of tunnel construction, it is quite challenging to conduct a thorough and all-encompassing examination of every factor that impacts tunnel construction. Additionally, it is essential to consider the accessibility of relevant information during engineering construction. This necessitates a comprehensive analysis of both the degree of influence on tunnel risk and the availability of information [38; 39; 40; 41; 42]. For the risks that may occur in tunnel TBM construction, the corresponding indicators are selected to reflect the degree of danger. For example, the elastic deformation energy index is usually used as the main evaluation index when evaluating the risk of rock burst. The elastic deformation energy index is the ratio of the elastic strain energy stored in the rock sample to its ability of plastic deformation dissipation before the peak strength of the rock is reached. To a certain extent, it can be used to directly reflect the degree of danger of rock burst. Similarly, the risk of sudden water intrusion can be expressed by the groundwater level. The higher the value is, the greater the probability of risk occurrence is. The risk of landslide can be expressed by the rock integrity coefficient. The smaller the value is, the more fragmented the rock is in the tunneling process, and the more likely a landslide is. When selecting risk evaluation indicators for TBM construction, the first consideration is to select representative indicators of various risks, which can directly or indirectly reflect the actual situation of geological conditions, construction environment, equipment status, and human activities. In this paper, 15 factors, including elastic deformation energy index (\(I_{1}\)), groundwater level (\(I_{2}\)), rock integrity coefficient (\(I_{3}\)), gas monitoring data (\(I_{4}\)), cutterhead torque (\(I_{5}\)), ventilation system flow (\(I_{6}\)), surrounding rock classification (\(I_{7}\)), cutterhead speed (\(I_{8}\)), entrance support effect (\(I_{9}\)), water seepage (\(I_{10}\)), protective layer thickness (\(I_{11}\)), guiding system monitoring data (\(I_{12}\)), underground space monitoring data (\(I_{13}\)), underground pipeline detection data (\(I_{14}\)), and surrounding building displacement monitoring number (\(I_{15}\)) are selected to establish a tunnel risk evaluation index system. Referring to the classification standards of tunnel risk in literature, the occurrence probability of tunnel risk is divided into four grades: the ideal state (\(V_{1}\)), low-risk state (\(V_{2}\)), medium-risk state (\(V_{3}\)), and high-risk state (\(V_{4}\)). These four grades correspond to different states of indicators. Before the formal construction, the surveying unit conducted specific detection on different sections of the site and summarized the parameter range for rock formation and rock properties in this project. Therefore, this paper will use these parameter ranges as criteria for dividing risk levels. According to the data obtained from the preliminary survey and on-site measurement, relevant data are input into different grades, such as the elastic deformation energy index obtained from the on-site measurement, which is divided into different intervals according to the actual rock and rock properties obtained from the preliminary survey. For example, the interval [0, 2] represents no rockburst risk, the interval [2, 4] represents a weak rockburst risk, the interval [4, 6] represents a medium rockburst risk, and an interval greater than 6 represents a strong rockburst risk.