Dynamic risk evaluation method of collapse in the whole construction of shallow buried tunnels and engineering application

The collapse is the most frequent and harmful geological hazard during the construction of the shallow buried tunnel, which seriously threatens the life and property safety of construction personnel. To realize the process control of collapse in the tunnel construction, a three-stage risk evaluation method of collapse in the whole construction process of shallow tunnels was put forward. Firstly, according to the engineering geology and hydrogeology information obtained in the prospecting stage, a fuzzy model of preliminary risk evaluation based on disaster-pregnant environment factors was proposed to provide a reference for the optimization design of construction and support schemes in the design stage. Secondly, the disaster-pregnant environment factors were corrected based on the obtained information, such as advanced geological forecast and geological sketch, and the disaster-causing factors were introduced. An extension theory model of secondary risk evaluation was established to guide the reasonable excavation and primary support schemes. Finally, the disaster-pregnant and disaster-causing factors were corrected according to the excavation condition, an attribute model of final risk evaluation for the collapse was constructed combined with the mechanical response index of the surrounding rock. Meanwhile, the risk acceptance criteria and construction decision-making method of the collapse in the shallow buried tunnels were formulated to efficiently implement the multi-level risk control of this hazard. The proposed method has been successfully applied to the Huangjiazhuang tunnel of the South Shandong High-Speed Railway. The comparison showed that the evaluation results are highly consistent for these practical situations, which verify the application value of this study for guiding the safe construction of shallow buried tunnels.