Study On Durability Retrogression Rule Of The Shield Tunnel Concrete Segments And Its Service Life Prediction

Our country has numerous cities governed across rivers, seas. The bridges connecting banks of rivers, lakes, and harbors have been playing great roles in the construction of national economy. Comparing with bridges over rivers, lakes and seas, the construction of underwater tunnel has some priorities of little of land compensation, easy to demolish and remove, little effect to the ground, no influence to the capacity of traffic on the watersurface, no influence to the changes of adverse climate, good project covert , obtaining a strong ability to resist the damae of the war, which has been taken seriously by all the cities. Comparing with concrete structure in the atmosphere circumstance, the structure of shield tunnel concrete segment shall serve in severe conditions, the problem of duration is complicated and serious. This essay starts analysis in theory analyzing the lapse mechanism of the structure of shield tunnel concrete segment under the force of every single component, the model and the rule of duration retrogression, the theory of combination of superior reinforcement concrete, and creat a service life predict model based on the principle of load capacity. The context includes:1,Carry out analysis to the special working circumstance of the structure of shield tunnel concrete segment and acquire the main component of destroying the duration are concrete carbonization, chlorine ion erosion, sulfate erosion, metro scattered current erosion and their coupling interaction.2,Make analysis to the foregoing 4 types of lapse mechanism as well as the rule of duration retrogression,testify the depth-predict model of concrete carbonization recommended in the specification.3,Make use of the evolutional equation of concrete failure to describe the erosion of concrete by sulfate, finalized the beginning time of concrete erosion and the relations between concrete standard compression strength and dynamicmodulusofelasticity.4,Introduce the forming of the metro scattered current, analyse the mathematics model of the distribution of the scattered current, obtain the the distribution of the scattered current and respective components effects through theoretic anaylisis and numerical simulation.5,Study the mechanic capability of the tube structure of shield tunnel concrete. Take the example of Nanjing subway, create finite element emulation using MADIS software towards the structure of shield tunnel concrete segment and discovered that the maximum flexural moment happens at the bottom, the maximum flexural moment happens on both sides. 6,Produce the carrying capacity of the structure of shield tunnel concrete segment duration retrogression model, applying which to predict and calculate the service time of the structure of shield tunnel concrete segment used near to southeast coast, Nanjing Yangtze river-crossing Hangzhou metro and Xining metro.7,As a result of the relative high level of salt content underground in Xining and the erosion of the concrete is so serious that high-performance concrete should be studied for the purpose of using in this adverse circumstance.