Smart Sensing Of Multi-Scale Deformational Information And Large-Deformation Control For Shield Tunnel Structures

New challenges and opportunities arise,while China’s urbanization process confronts the era of information and intelligence.Intelligent operation and maintenance of infrastructures has grown with increased importance to achieve sustainable urban development.From the consolidation of national defense to the improvement of people’s livelihood,shield tunnels have played an essential role in the historical time and space coordinates of China’s urban construction and development process.China has the longest mileage of various kinds of shield tunnels in the world,mounting up to nearly 10,000 kilometers of total length in operation.This thesis presents a systematic study on the smart sensing of shield tunnels to collect spatial multi-scale deformational information,and the large-deformation control for shield tunnel structures.The goal of the research is to achieve a more refined assessment of the tunnel’s deformational and structural states,and meanwhile,to arrive at an improved understanding of the deformation control for shield tunnel structures when deformation gets large.Research work has been carried out systematically,ranging from background introduction,theoretical analysis,strategy selection,technology development,experimental validation,result optimization,and engineering applications.The thesis consists of the following main sub-topics:1.The basic composition,theoretical principles,and strategy selections for the smart sensing of multi-scale spatial deformational information for shield tunnel structures.The multi-scale information set can be generally divided into three levels: the system-scale level,the component-scale level,and the material-scale level.Relevant theoretical analysis is applied to propose a spatial multi-scale deformation fusion-sensing strategy,aiming at enhancing the evaluation capability for the real performance of shield tunnel structures at a more refined level,and improving the treatment and mitigation capability for tunnel structural damage.2.Smart sensing of the longitudinal deformation and damage accumulation of a tunnel based on system-scale field monitoring.Tunnel longitudinal deformation and its associated lining damage response is studied on the basis of the monitoring records of an existing shield metro tunnel heavily influenced by double-sided offloading effects from adjacent deep-large excavations.Effects of different temporal and spatial influencing factors are depicted in detail.It is concluded that the longitudinal average curvature of the shield tunnel structure relates closely to the degree of structural damage observed.3.Studies of the component-scale longitudinal deformation and its characteristics of shield tunnel structures.A novel smart sensing technique named fiber optic sensor network is proposed,which enables refined sensing of the tunnel’s complex long-term inter-ring behaviors in its longitudinal direction,in terms of a fully 3D-decoupled observation of the shearing and bending movements between lining rings.Long-term monitoring records reveal that the shearing and bending deformation modes exist simultaneously,but the two modes of deformation appear to exhibit considerable independence between each other,where the shearing mode tends to dominate the tunnel’s inter-ring behaviors.New insights are brought about from the sensing records of the tunnel’s circumferential performance with regard to the deformation evolution patterns for shield tunnel lining rings with existing structural damage.4.Studies of the smart sensing technologies for the shield tunnel’s circumferential deformation at the component-scale level through its application in full-scale lining ring tests.Both distributed fiber optic sensing technology and digital image correlation technology were employed in full-scale experimental tests to reveal the deformation states and structural performance of the staggered-jointed lining rings under off-loading as well over-loading conditions.The relationship among the monitored distributed deformation information,the evolution of lining’s structural performance,and the structural damage accumulation is discussed.By combining the distributed strain data with a non-linear fiber-based mechanical model,a holographic physical information set is established for the whole mechanical process of the lining ring structure.5.Smart sensing technology development for material-scale level deformation of shield tunnel structures.Concept and design of a novel short-gauged Brillouin fiber optic sensor are proposed to realize early detection,as well as accurate measurement,of cracks developed in shield tunnels with a longdistance-coverage capability in a distributive manner.On this basis,the response of crack-induced Brillouin gain spectrum is deduced theoretically,simulated numerically,and verified subsequently by laboratory experiments.With a pilot field application,a large-scale deployment of the proposed sensor and the associated in-situ loading tests were carried out.The sensor’s field instrumentation procedures and its superiority in terms of its sensing capabilities have been validated.6.Large-deformation control of shield tunnel structures based on a micro-disturbance double-fluid grouting technique.Through an in-situ field grouting test,the real deformation response of shield tunnel linings is investigated under grouting treatments.A comprehensive database of the tunnel structural behavior under grouting impact is established by systematically setting diverse geometric grouting parameters of the testing.The spatial and temporal evolutionary characteristics of lining deformation and grouting efficiency are explored based on obtained sensing data.Furthermore,a numerical simulation framework is proposed on the basis of the Material Point Method to explicitly model the grouting process.The framework is validated by the good agreement between the numerical and experimental results.