Tunnel Air Shaft Excavation Technology After Shield Tunnelling
The interval tunnel of Beijing Metro Line 17 adopted the construction technology of a shield first passing through and then transversely excavating the air duct.The upper air duct was excavated across the shield tunnel to the end wall,and the lower air duct was excavated adjacent to the shield tunnel.Under the protection of the secondary lining structure of the upper air duct,the soil on both sides of the shield tunnel was excavated by the inverted shaft wall,the secondary lining of the shaft was constructed,and the side wall and bottom plate of the lower air duct within the scope of the shield tunnel were not constructed to ensure the safety of the later construction.The hoisting holes were reserved through the middle plate of the air duct,the segments were removed ring by ring,and then the side wall and bottom plate of the lower air duct within the scope of the shield tunnel were constructed.Before the horizontal excavation of the air duct,it was necessary to take reinforcement measures such as radial grouting,longitudinal tension and circumferential support for the segments outside the air duct to prevent the deformation of the shield tunnel and reduce the surface settlement.Due to the need for multiple force conversions,the load-structure method was used to analyze the internal force of the secondary lining structure at each stage.The stratum-structure method was used to analyze the deformation and stress of each stage of excavation for air duct,shaft and segment demolition.The results show that the surface settlement meets the requirements.The monitoring results show that the surface subsidence reaches 9.91cm.The main reason is that after the shaft is excavated to the end,the supporting structure cannot be closed into a ring to form an overall force system due to the confined water and the failure to seal the bottom in time,resulting in the surface settlement exceeding the standard.
万方数据
维普
