Design And Research On Unboned Prestressed Concrete Of Pressure Tunnels

The main content of this article is based on the design of low covered pressure tunnel in Liaoning Dahuofang Reservoir Water Diversion Project (2nd stage), and to raise the unboned prestressed encircled anchorage method to solve the problem of preventing cracks in lining of pressure tunnels in low covered and unfavorable geologic conditions. Five representative sections in Liaoning Dahuofang Reservoir Water Diversion Project (2nd stage) has been analysed with finite element method, and find the unbonded prestressed method can satisfy the need of every design condition. The chosen method has characteristic as follows: proper price in economic, practical in technology, easy on performing and safe in structure, so it can meet the need of tunnel's long-term running in complex geology condition.This article mainly concerned the content as follows:(1) It mainly concerned on the reason why choose unbonded prestressed concrete lining technology. The main way is to investigate the application and new development of prepressed concrete lining in china and foreign countries and research on whether it can be used in this project.(2) Use the finite element software ANSYS to make model for consecutive strands and unbonded prepressed concrete lining. Build the reciprocity relation of the cells in consecutive strands and cells in RC, analyse the stress and transmogrification of consecutive strands and RC to make sure the design parameter can meet the need of specification.(3) Research on the key technology of the post-tensioning prestressed encircled anchorage method, including studies of concrete mix in lining and notch of anchor part, anchor and preservative system, unwanted excavattion and water-stop of ring parting, and based on those studies to raise the reliable application measures for post-tensioning initial stress methode , make suggestion for usage of those technologies.Unboned prestressed concrete lining was infrequent usage in 90th, until it was used in flood and sediment discharge tunnels of the Xiao Lang Di Project first time and filled up the internal blank . This design gains experience on usage of unboned prestressed technology in the Xiao Lang Di Project and other projects, as a result, the problem of how to design lining of tunnels in low covered and unfavorable geologic conditions can be solved.