# Hazard Prediction of Water Inrush in Water-Rich Tunnels Based on Random Forest Algorithm
## 4 Results: Engineering Case Verification  
The Yuanliangshan tunnel Yuanliangshan (1961); Yuanliangshan (1961); Yuanliangshan (1961) is located in Youyang County, Chongqing City, with a total length of 11,068 m and corresponding mileage of DK351+465-DK362+533. The maximum burial depth of the area where the tunnel is located is 780 m, the surrounding rock grades of the tunnel are mainly Class II, III, and IV and there are 11 faults that have a large influence on the tunnel. The main geological structures crossed by the tunnel are the Maoba Syncline, Tongmaling Anticline, and their associated or secondary fault structures. The lithology of the strata through which the tunnel passes mainly consists of limestone and shale, and the Maoba syncline area is a closed, basin-like structure that is soluble and impervious to water. It is easy for the convergence, infiltration, and circulation of atmospheric precipitation, the acceleration of the dissolution rate of limestone, and the formation of cracks, karst caves, karst pipes, or large, high-pressure, and water-rich karst caves. During tunnel construction, five deep buried filling karst caves were encountered, which were induced by factors such as high pressure, rich water, and karst. During the construction process, dozens of water inrush accidents occurred. The geological conditions related to the Yuanliangshan tunnel are shown in Figure 7, and a photo of the water inrush accident in Yuanliangshan tunnel is shown in Figure 8. This article selects five typical tunnel water inrush accidents from the relevant literature recorded by scholars, and these five accident sections are located in five karst cave areas with inadequate geology conditions, resulting in a high hazard of water inrush accidents. According to the on-site situation of the Yuanliangshan tunnel, the specific evaluating indicators are shown in Table 4. The water inrush in Table 4 is classified into hazard levels based on Table 2, with sections 1-5 classified as IV (4), IV (4), IV (4), II (2), and III (3), respectively. According to the data preprocessing scheme mentioned in this article, Table 5 can be obtained by processing the hydrogeological conditions related to the Yuanliangshan tunnel in Table 4.  
The preprocessed data in Table 5 are brought into the water inrush hazard prediction model of the water-rich tunnel established in this article to predict and analyze the hazard level of water inrush in five sections of Yuanliangshan tunnel. The implementation process is shown in Figure 9 and the comparison between the actual hazard level and the predicted hazard level is shown in Table 6.  
Figure 7: Geological conditions of Yuanliangshan tunnel. According to the comparison between the predicted results and the actual results in Table 6, we can see that, of the five water inrush accident sections selected in this article, the predicted results of four sections are correct, with an accuracy rate of 80%, indicating that the overall performance of the model is good. However, there is a certain deviation (inconsistency) in one section (Section 4), in which the actual hazard level is Level II but the predicted result is Level IV. After analysis, it was found that the main reason for the high prediction results is due to the high level of hazard associated with the stratigraphic lithology, inadequate geology, rock dip angle, and surrounding rock grade. An explanation