Model Test On Joint Detection Of Defects In Mortar Layer Of Ballastless Track And 3D Forward Simulation

With the continuous development of high-speed railway in China,ballastless track has been widely used in railway engineering.However,long-term train load and complex external environment will cause damage such as void and void in the mortar layer of ballastless track structure.Therefore,it is of great engineering value to reasonably use nondestructive testing technology to determine the specific situation of damage in mortar layer.At present,GPR method and impact echo method are widely used in the non-destructive testing technology of ballastless track disease detection.GPR method has the advantages of high detection speed and efficiency,but it is easy to be affected by steel bars and other materials.While impact echo method has high detection accuracy,its disadvantage is that the detection speed is relatively slow,and the two methods are reasonable If the damage detection technology is combined to detect the structure,it can ensure the detection accuracy and speed.In this paper,the joint test of ballastless track model is carried out.Two kinds of non-destructive testing technologies,ground penetrating radar method and impact echo method,are used to test the ballastless track model.The joint testing method suitable for ballastless track detection is summarized,and the propagation characteristics of electromagnetic wave in ballastless track model are simulated by MATLAB software programming.The main contents of this paper are as follows:(1)The physical model of ballastless track is designed and made,and the GPR instrument is used to detect the physical model.The relevant software is used to further analyze the detection image of mortar layer disease in the model.By analyzing the detection image of the mortar layer disease of the ballastless track model,the feasibility and applicability of GPR in the detection of ballastless track structure are determined.(2)The impact echo method is used to detect the damage and disease in the physical model of ballastless track.In the later stage,the time-domain diagram and frequency-domain diagram obtained by the acquisition and analysis software are analyzed to preliminarily determine the location of the disease.The software is used to analyze the frequency spectrum of each measuring point in the measuring area to get a three-dimensional slice cloud chart,which is convenient to judge the disease location directly.After determining the approximate location of the disease,the specific depth of the disease can be calculated by analyzing the frequency spectrum of each measuring point near the disease area.In the same case,the advantages and disadvantages of GPR and impact echo detection models are compared and analyzed,and a reasonable joint detection method is proposed.(3)Through the program of MATLAB software,the three-dimensional forward simulation of the detection of ballastless track internal diseases by GPR is carried out,and thewave field energy snapshot of electromagnetic wave propagating in the model is obtained.Compared with GPR test,the electromagnetic wave energy map obtained by forward simulation of various models is analyzed to verify the propagation characteristics of electromagnetic wave in ballastless track,and the necessity of joint detection is also illustrated.