Operation Status Of Prestressed Concrete Liner In The Xiaolangdi Desilting Tunnels

It is economical and pragmatic to adopt post-tensioned unbonded pre-stressed concrete to take place of steel plate in tunnel liner construction to withstand high internal water pressure in pressure tunnel of Waterway Engineering. The technology of post-tensioned unbonded circular anchored pre-stressed concrete tunnel liner which adopted in the Xiaolangdi desilting tunnels has filled in the blank of application of unbonded pre-stressed concrete in waterway engineering in our country. The use of the new type of the structure with best development potential makes our country enter the international advanced range in the area of technology research and application. The Xiaolangdi desilting tunnels, which were built from 1998 to 1999, have been operating over seven years. During the past 7 years, the tunnels have undergone various designed working conditions. Millions of observation data has been collected by the 160 pieces of instruments embedded in the three tunnels.What the thesis mainly focuses on is, with the methods of mathematical statistic analysis and finite elements calculation, researching the stress and strain distribution of the tunnel liner under the conditions of various temperature load and water pressure, and the analysis of autogenous volume deformation of concrete. On the basis of the distribution and the deformation, the safety state of desilting tunnels can be identified reasonably. The above conclusions definitely mean a lot to the establishment of pre-warning and forecast system of tunnel safety state, to the optimization of the homo-structure design and to the popularization of the new type of structure.The main contents of the thesis are summarized as following:(1) Analysis of variation law for the stress and strain of the pre-stressed concrete liner under the condition of various temperature load and water pressure.(2) Analysis of variation law for the autogenous volume deformation of the pre-stressed concrete.(3) According to the variation law for the stress and strain of the pre-stressed concrete liner, the desilting tunnels safety state could be identified.(4) Several laws which deduced form millions of observation data would be verified by using the three-dimension finite element method.