Study on Multi-Level Safety Risk Assessment of Two-Line Three-Step Construction of Long-Span Shallow Buried and Hidden Excavation Tunnel

In the construction of long-span shallow buried and hidden excavation tunnel, the two-line three-step construction can avoid the risk caused by the structural system transformation during the demolition of temporary support. However, the two-line three-step method is applied to the underground tunnel construction technology is complicated, the stress system is complex, and the risk sources are numerous. Especially when crossing the soft and complex stratum and shallow tunnel buried and hidden excavation, the difficulty of tunnel deformation control and construction risk are significantly improved. To improve the safety risk control level in the construction process, the paper analyzes the risk factors of the two-line three-step construction of the long-span shallow buried and hidden excavation tunnel, carries out multi-level identification and fuzzy comprehensive evaluation of the risk factors, and determines the major risk sources. The results show that the construction process is a major and high-risk behavior, and the main risk is from management risk and technical risk, among which personnel management, safety education, and safety supervision are the biggest risk sources, and prevention work should be done for important risk points. The results of safety risk assessment have a high-reference value for the safety management practice of the two-line three-step construction of long-span shallow buried and hidden excavation tunnel.