The Research On Detection And Image Regualation Of Cavity Under The Reinforcement Based On GPR

With the rapid growth of China's high-speed railway line mileage and the increase in the use of ballastless track on high-speed railways,the number of ballastless track diseases has started to increase,and it has gradually become an important issue in ensuring railway safety.As one of the most common defects in ballastless tracks,cavity detection has always been the main task of the railway work department.The traditional subgrade detection method will cause damage to the railway lines,and the detection speed is slow,and a lot of manpower and material resources are consumed.All these have put forward new requirements for the detection methods of railway lines.As a new non-destructive testing technology,ground penetrating radar technology has aroused the attention of the relevant departments and carried out a pilot study in the field of high-speed railway offline detection.This paper adopts the method of software simulation and experiment.Firstly,the GprMax software is used to simulate the cavity damage model of ballastless track,and the simulation results are processed and analyzed by using Matlab software.Then set up a model in the laboratory,use the ground penetrating radar system to detect and investigate the detection results.The main research contents are as follows:(1)The model of steel bar and cavity was built separately,and analyze the radar image which background has been removed.Grasping the characteristics of the radar image when the ground penetrating radar electromagnetic wave encounts the steel bar and cavity,which will provide a theoretical basis for the determination of the reinforcing steel bars and cavity's position.(2)According to the working principle of ground penetrating radar and the principle of electromagnetic wave propagation,the appropriate ground penetrating radar parameters are calculated according to the formula and forward simulation of the reinforcement and cavity model is performed by using GprMax software.By using ground penetrating radar to simulate the model of cavity with single,single-layer,double-layer and triple-layer reinforcement,and analysis its affects to the cavity radar image after removing the direct wave and background noise.(3)Experiments by embedding reinforcing steel and foamed plastic in the sand were conducted by using the RIS ground penetrating radar system produced by the IDS company in Italy.The foamed plastic represents the cavity and the sand represents the concrete.The reinforcement spacing,sand thickness and the size of foam are necessary to account to design a suitable detection method.After removing the ground direct wave,background noise and F-K migration,analysis different situation of reinforcements' affects to the cavity radar image.