Dynamic Monitoring Of Tunnel Surrounding Rock Deformation Disaster Based On Fiber Grating Sensor

As people pay more and more attention to the safety,durability and normal use of large and important infrastructures,the development of research and monitoring systems for infrastructure safety monitoring came into being.Unlike traditional manual inspection methods,safety monitoring can monitor the operational status of the structure in real time and is relatively dynamic.The tunnel engineering environment is characterized by complexity,concealment,and suddenness.At present,there are few types of intelligent sensing sensors widely used in the tunnel field,and the monitoring parameters are single.Fiber grating sensing technology,with its own advantages such as safety and reliability,high measurement accuracy,durability,and low maintenance costs,provides new methods and ideas for solving the safety,efficiency,and intelligent perception of the basic information of tunnel mining method construction.This thesis grasps and understands the research background and significance of these projects at home and abroad by reading relevant literature,collecting and consulting the current status of smart sensor monitoring during tunnel mining construction,and analyzing the deformation of the surrounding rock of the tunnel.Relying on the Qipanliang Tunnel on the Yanchong Expressway of this project,this paper mainly uses fiber grating sensors to monitor the key sections of tunnel surrounding rock deformation.The main research contents are as follows:(1)Based on the fiber transmission theory,the reflection spectral characteristics and distribution of fiber gratings are theoretically calculated.The effects of fiber grating intrinsic parameters,such as the length of the grating region and the change in refractive index,on the reflection spectral characteristics are studied.The characteristics of strain and temperature sensing of fiber gratings are discussed.(2)Starting from the practical application of fiber gratings in tunnels,three different packaging methods for attaching fiber gratings on the surface of the substrate were proposed.The fiber grating and substrate strain sensing transmissionmodels were established.The mathematics of the actual strain of the substrate and the fiber grating sensing strain were theoretically derived The equation proposes the strain sensing transmission factor of fiber grating,reveals the strain sensing distribution law of fiber grating and substrate in the range of pasting length,analyzes the factors affecting strain sensing transmission of fiber grating and substrate,and validates the strain sensing transmission effect through experiments.(3)Relying on the actual site monitoring of the project,the real-time monitoring of key positions on the tunnel construction site is performed.At the same time,the errors caused by the demodulator,zero point drift,and on-site temperature on the measurement results of the fiber grating sensor are analyzed.Starting from the on-site deployment of technology and sensors,a more targeted improvement method was proposed to improve the widespread application of fiber grating sensors in tunnel engineering.(4)The effects of changes in weathering degree and mining method construction disturbance on the structure of the feldspar granite were analyzed through polarized light microscope experiments from the perspective of rock microstructure and mineral composition.The range of damage area of surrounding rock excavation under the action of mining method was determined by sonic test,and the deformation modulus of rock mass was estimated by empirical formula.Finally,the rock mass structure after construction is analyzed by ground penetrating radar.(5)The numerical simulations of different construction site schemes of the tunnel are performed,and the deformation characteristic curves under the field monitoring and numerical simulation are fitted to obtain the whole curve of the surrounding rock deformation during the excavation of Qipanliang tunnel.