Cause Analysis and Treatment Measures for the Collapse at the Entrance of Diaoyutai Tunnel

An in-depth analysis was conducted on the causes of the collapse at the entrance of the Diaoyutai Tunnel on the Chi-Qi Expressway, and corresponding measures for dealing with the collapse were proposed. The effectiveness of the collapse treatment was verified through on-site monitoring and analysis. The research results indicate that the collapse of the Diaoyutai Tunnel entrance is the result of a combination of various factors such as terrain, geology, rainfall, and improper construction measures. Among them, terrain and geological conditions are the internal factors that cause the collapse, while rainfall and improper construction measures are the external factors that induce the collapse. Based on the above influencing factors and combined with the actual situation of the tunnel entrance, a comprehensive treatment plan of temporary support+permanent protection has been proposed, which includes reinforcement of the tunnel arch, backfilling of the tunnel face with back pressure, unloading of the collapsed body, double layer small conduit support at the entrance, extension of the open cut tunnel, and protection of the roof and forward slope anchor rod frame. The on-site inspection and monitoring data indicate that the treatment measures for tunnel entrance collapse are appropriate, and the engineering effect is significant, achieving the expected purpose.