Research On Evolution Mechanism Of Structural Performance Degradation For Shield Tunnel Under Environmental Erosion

At present,with the rapid development of China’s national economy and urbanization process,large tunnel,urban subway,city comprehensive pipe corridor and other large shield tunnel project is emerging.China has becoming the country which has the largest number of shield tunnel project,the the largest construction scale,the most difficult technical complexity and the fastest development speed.In the context of the large number of shield tunnel projects in China,it can be predicted that the safety performance and durability of the service life of shield tunnel will be the focus of the researchers of engineering science and technology,and will also become an important direction in the research field of shield tunnel lining performance.In view of this,the evolution mechanism of structural performance degradation for shiled tunnel under environmental erosion is studied in this paper,and the results will have important theoretical and practical significance for the future design,construction and long-term safety of large-scale shield tunnel.Supported by the National Key Basic Research Program of China(973 Program)"Research on the long term safety and its prediction method of underground structure under the complex environment",the Key Consulting Project by the Chinese Academy of Engineering“Research on the structure security technology and countermeasures of large-scale underwater tunnel" and many other major national research projects,the theoretical analysis,model tests,corrosion deterioration tests,numerical simulation and many other methods are carried out in this study.The evolution mechanism of structural performance degradation for shiled tunnel under environmental erosion is studied comprehensively and systematically from the four levels of the environment,materials,components and structure.The research results have important guiding function to ensure the safety service performance of the shield tunnel lining structure under the action of erosive environment in the whole life cycle.The main work and research results are as follows:(1)By means of theoretical analysis combined with data research,the complex environment characteristics of shield segment lining structure during service period were proved,the present situation and characteristics of typical shield tunnel lining under the coupling of erosion environment and load environment were investigated and analyzed.(2)By means of theoretical analysis,numerical simulation of erosion ion migration,the corrosion ionization analysis model of shield tunnel lining structure was established,the distribution regularity of erosion and deterioration of shield tunnel lining structure under corrosive environment was proved,the erosion regularity of the lining structure under seepage water loss condition and seepage water failure condition was studied.(3)Using the methods of indoor concrete accelerated carbonation test,accelerated corrosion of concrete and steel corrosion accelerated corrosion test,and combined with acoustic emission nondestructive detection technology,the effect of concrete carbonation and steel bar corrosion on the mechanical properties of shield tunnel lining structure material was studied,the evolution of tunnel lining structural material under the action of corrosion was revealed.(4)Considering the normal use conditions of shield tunnel lining structure in the soil and water load environment and the surrounding ion erosion environment in the long-term service,accelerated corrosion damage test of bearing segment was carried out.The deformation behavior of shield segment under different load conditions and different degrees of corrosion deterioration was proven,the occurrence and development process of erosion,deterioration,cracking and damage of shield segment was revealed,the influence of reinforcement corrosion on the internal force,deformation,mechanical parameters,crack propagation and failure morphology of the segment was clarified.(5)Using the indoor similar model test means,the influence of erosion deterioration on the mechanical performance of segment lining was studied from the lining structure level.The mechanism influence of joint corrosion defect on the segmental lining was clarified.The stress characteristics of the double-lining structure after the secondary lining repaired,and the stress characteristics of double-layer lining under secondary corrosion were further proven.Meanwhile,the performance evolution law of the shield tunnel lining structure degradation,repair and then degradation was revealed.(6)Using the damage mechanics theory,the mechanics theory of the composite material and the numerical simulation method,the model of shield tunnel lining structure considering the effect of structural erosion was constructed.The evolution law of the performance degradation of the segment lining structure was explored,and the performance evaluation and prediction of the active shield tunnel were carried out.