Study On Nondestructive Testing Technology Based On Ground Penetrating Radar And Ultrasonic Testing In Pavements

As Chinese highway construction shifts from high-speed development to high-quality development,highway inspection and maintenance require more and more rapid,nondestructive and intelligent methods.However,traditional inspection methods have been unable to meet the needs of building a powerful transportation country.Ground penetrating radar(GPR)and ultrasonic testing(UT),as one of the mature and advanced non-destructive testing methods,combined with new technologies such as deep learning(DL),can achieve rapid,non-destructive and intelligent detection and evaluation of road structures.Beacuase these two methods can effectively improve the efficiency and accuracy of road detection and maintenance,they are one of the development directions of road inspection and maintenance technology in the future.This paper summarizes the existing theoretical research and practical application of GPR and UT.Aiming at key issues such as the propagation attenuation mechanisms of electromagnetic wave and ultrasonic wave and internal disease detection in road structures,multi-dimensional analogy analysis of GPR and UT are done through theoretical analysis,numerical simulation and laboratory test.The law of ultrasonic propagation and attenuation in asphalt concrete and influencing factors are clarified,and the characteristics of typical road diseases are also summarized.Meanwhile,combined with the actual measurement on site,the finite difference method and DL,the study has clarified the judgment basis of the typical diseases of the road structure in the radar image,and has realized the intelligent identification and positioning of the diseases.Aiming at the analogy analysis of GPR and UT,this paper explains the similarities and differences of detection principles,the unification of wave equations,the equivalence of medium characteristics and the analysis of the law of propagation attenuation.The numerical simulation methods are also used to study the relationship between electromagnetic waves and ultrasonic waves.For the medium action characteristics,the main parameters of the two waves have a certain equivalent relationship,and the response to the medium is similar.Aiming at the attenuation characteristics and influencing factors of ultrasonic waves in asphalt concrete,this paper theoretically analyzes scattering attenuation and absorption attenuation,and establishes a meso-model through the finite element method to study the impact of incident frequency,aggregate particle size,temperature and other factors.The frequency range is 20-60 k Hz and the temperature does not exceed 40 ℃,and the ultrasonic image judgment basis for typical diseases such as cracks,looseness and voids are also summarized.Aiming at the judgment basis and intelligent identification and positioning of typical diseases of subgrade and pavement,this paper combines the finite difference method and the actual measurement results to compare and analyze the influence of frequency on the detection results.It is recommended that the frequency range of shallow diseases in the road structure is1-2 GHz.This research aslo has summarized radar image judgment basis for typical diseases such as cracks,voids or voids,looseness,uneven settlement and subsidence.Combined with the object detection model Your Only Look Once(YOLO)and three-dimensional GPR,the construction of the data set is introduced in detail and the training and detection of the YOLO series models are also compared.Finally,the intelligent identification and positioning of concealed cracks in the radar image is realized.