Abstract:

The Yellow rivercrossing tunnel on the central route of southtonorth water transfer project is a pressured water transfer tunnel. The tunnel is excavated by shield machines, with the segment lining as the primary reinforcement. Prestressed castinsitu concrete lining is installed for the tunnel as the final lining so as to ensure the safety of the tunnel structure. Prestressing ducts are embedded in the castinsitu lining concrete, steel stands are installed and circular tensioning is made to achieve the prestressing of the lining concrete. In this paper, the process, technical requirements, key points and countermeasures for the tensioning are presented. The relationship between the extended length of the steel strands and the friction coefficient is obtained by means of model calculation and data setting. The practice shows that the circular tensioning technology used in Yellow rivercrossing tunnel can meet the requirements of safety of the water transfer structure. 

Key words: shieldbored tunnel, secondary lining, prestressing, circular tensioning