Numerical Simulation Of Structural Deformation Of Highway Tunnel And Research On Fiber Bragg Grating Monitoring

With the unprecedented development of infrastructure especially in highway construction, the number of highway tunnels has been increasing and the speed of construction continues to accelerate in western mountainous area. Due to the limits of geological conditions and construction, there are different degrees of tunnel disease problems in tunnels which are under construction or had been built. Therefore, analyzing and monitoring the stress state of the tunnel in the process of tunnel construction and operation, and warning of impending tunnel disease accurately, play an important role in guaranteeing the tunnel safety and quality.The comparative study of stress state resulted from FEM numerical simulation and on-site monitoring in Yunnan Tianxin Tunnel was conducted to guarantee the safety of tunnel construction and operation. It mainly includes the following aspects of work:1. This study analyzed numerical simulation theory of tunnel construction and realized them in ANSYS. Based on the general situation of Tianxin Tunnel, the plane strain computation model was established by the FEM method. And the method of applying virtual support force to release the stress of initial stress gradually and the technique of birth and death of element were adopted to simulate the bench cut excavation.2. The regularities of tunnel structural deformation and stress was obtained by analyzing displacement field and stress field of surrounding rock and internal force of secondary lining.3. According to the results of FEM simulation, the FBG monitoring scheme was determined. The FBG sensor network which consisted with secondary lining strain monitoring subsystem and rock pressure monitoring subsystem was established by FBG sensors for long-term health monitoring of the tunnel.4. The comparative study of results from FEM numerical simulation and on-site monitoring showed that:except the secondary lining strain of vault, the stress states of the tunnel obtained by numerical simulation and on-site monitoring were consistent. The strain value of on-site monitoring was approximately60%-70%to the simulation value. And the rock pressure value of on-site monitoring matched up with the simulation value. The strain monitoring value of vault (309.83με～327.23με) has been detected larger than simulation value (209.37με), which matches well the crack phenomenon of vault. Therefore it’s significant to focus on the long-term monitoring of vault.5. Applying the method which combined the numerical simulation and on-site monitoring to tunnel engineering could warn of impending tunnel disease accurately. The defects of single on-site monitoring method such as poor predictability were made up effectively by comparative study, which proved that this method was effective in ensuring the tunnel safety.