Structure Improvement And Design Theory Research Of The Prestressed Tunnel Lining With Unbonded Circular Anchored Tendons

The prestressed tunnel lining with unbonded circular anchored tendons is a new type of tunnel lining, Apply mainly to the hydraulic tunnel which has high head pressure or poor adjacent rock condition. It has a lot of advantages over other tunnel linings, such as thinner in lining thickness, less materials and excavation volume, significantly reduce the project cost and construction difficulties, accelerate the construction schedule, fully utilize the high compression strength of concrete, and so on. It is a very promising form of lining in china's hydroelectric engineering and urban water supply works. But as a new type of structure, the design theory is not perfect, and it has no specific design specifications, many key technological problems have not yet been solved.The structure improvement, design theory research and 3D finite element methods of this new structure are discussed in this paper, using ANSYS as a calculate and analysis tool. The main contents are listed as below:The improvement of the structure. A new structure with one row of boxouts was proposed: first, the 3D finite element analysis method of this structure was discussed, which has some originality; after established the FEA model , the distribution of the pressure were calculated and analyzed; at last, the merits and advantages of the new structure of the one row of boxouts were discussed.The research of design theory. If the tensioning force and tendon's spacing were not properly designed., the circumference stress would not be uniform and the circumferential cracks would appear during tensioning. The proximity effect of circumference stress and axial stress created by the tensioning force were analyzed and simulated by function in this paper. The relations of tensioning force, tendon's spacing and circumference stress was explained in the paper, which have some reference value for the engineer design in the future.