Improved Detection Of Rebar And Diameter Estimation By Dual-Polarization GPR

In recent years,with the rapid development of national infrastructure construction,a large number of slender targets such as steel bars,cables and underground pipelines have been used in high-rise buildings and underground public facilities.However,these slender targets will inevitably be damaged by factors such as quality problems,construction damage and aging damage during construction and service,which seriously affects the normal service of infrastructure.Using non-destructive detection technology to detect infrastructure quickly and accurately and repair damaged targets can effectively maintain the health and safety of infrastructure and reduce unnecessary economic losses.Ground penetrating radar（GPR）is an efficient,portable and high-resolution nondestructive testing method,which has been widely used in underground target detection.In practical applications,ground penetrating radar measurement usually adopts a single-polarization mode,and the obtained underground target information is limited.Dual-polarization radar detection can obtain rich underground target data,which contains the geometric shape,material,internal structure and other information of the detection target.Therefore,compared with the traditional single polarization radar,the dual polarization ground penetrating radar has more advantages in detecting the underground slender target.The main work is as follows:（1）In this paper,a method of enhanced detection and diameter estimation of slender underground targets based on bipolar ground penetrating radar is studied.Firstly,the phase and relative scattering coefficient of the scattered field in TE and TM polarization modes are analyzed by using the analytical solution of the metal cylinder scattering signal,and it is proposed to improve the imaging of underground targets by shifting the phase of VV channel to-90°and making a difference with HH channel.The results of simulation data,laboratory tests and field tests show that the proposed algorithm(HH-VV^φ-90°)is superior to the other three polarization components in all cases.（2）The backscattering coefficient and phase information of reinforcement with different diameters are simulated in this paper,and the relationship between the phase difference of dual-polarization channel and the wavelength ratio of reinforcement diameter is established,which is verified by laboratory physical model tests.Finally,based on the relationship between the scattering coefficient and the phase difference and the wavelength ratio of diameter,a method for estimating the diameter of reinforcement in concrete structures is proposed.The research results of this paper provide a new method for reinforcement detection and reinforcement diameter of underground reinforcement,which is conducive to the development of ground penetrating radar technology in underground target detection.