| In recent years,China's tunnel engineering technology has developed very rapidly.The development of highway tunnels,railway tunnels,and urban subway tunnels can be described as the same progress.China has become the world's largest project in tunnel engineering.However,due to the influence of natural conditions such as hydrology,geology and climate,and human conditions such as construction and operation,the tunnel lining will have different degrees of quality defects and diseases.These defects and diseases will affect the operational safety and service life of the tunnel,and even lead to safety accident.In order to ensure the normal passage of the tunnel,the tunnel lining must be regularly tested and evaluated.At present,ground penetrating radar has become the first choice for tunnel detection.Because of the influence of many factors such as terrain,geological conditions,and construction quality,the cause and form of lining defects are more complicated.The detection and identification of lining defects in practical detection There are still some difficulties.Among the many defects in tunnel linings,the effective identification of lining voids is an important issue that cannot be ignored.In order to explore the laws presented by the radar image inside the tunnel lining,this paper is based on finite-difference time-domain(FDTD)method and passes GprMax3.0 The software carried out the following work:(1)Concrete cavity models of different sizes,different shapes,different depths,and different filling media were established.Forward modeling of these cavity models was performed to obtain radar maps.The radar imaging laws of these typical cavity models were analyzed and summarized,and the identification of voids was obtained.The theoretical basis of the size,depth,shape,and type of media contained in the cavity provides a theoretical basis for the actual measurement and effective identification of void targets.(2)The physical model test of the void was designed.The experiment of void model and data collection and arrangement were completed using RAMAC series radar X3M host and Groundvision2 data acquisition software.The background data is removed and the FK filter is applied to the collected data to obtain the effective information of the hollow hole target of the radar measurement result.The approximate position and size of the hollow target are found.The processed radar image and the forward simulation results are compared and analyzed.The accuracy of the simulation results was verified.(3)Combined with engineering examples,the tunnel lining inspection results are analyzed,the unconsolidated area behind the tunnel lining is found,and the position of the unconsolidated area is judged.The corresponding solution is proposed and the quality of the tunnel lining is evaluated.The analysis method of this paper provides a new idea for the detection and effective identification of tunnel lining voids.It lays a preliminary technical foundation and theoretical basis for the use of ground penetrating radar to detect,evaluate and diagnose the quality of tunnel lining. |
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