Research On Gridded Scaning Detection Method Based On Pattern Matching And Its Application In Detection Of High Speed Railway Structure Defects

The construction and development of major transportation infrastructure in China is rapid.The total mileage of highway and high-speed railway of China has been the first all over the world.In particular,the high-speed railway is planned to be completed in 2030 nearly forty thousand kilometers forming the eight horizontal eight longitudinal railway system.High speed railway is not only a bridge of different area,but also can promote the national development strategy: ‘The Belt and Road ’.High speed railway is known as the China manufacturing international name card.However,the major transport infrastructure is always facing the risk of disease and damage,such as concrete cracks,reinforcement corrosion,structural aging and other diseases in long-term operation.Therefore,good operation and maintenance is the key to ensure working of the transport infrastructure.Especially the detection of the under line structure of high-speed railway requires high speed,deep detection range.So a fast,accurate and simple defecte detection method is needed.The typical characteristics of the defect according to the traffic infrastructure can be detected by gridded scanning method based on pattern matching method.This method established the finite element model of typical diseases through numerical simulation getting the response of elastic wave to simulate grid scanning method.So combination under structure defect database can be achieved.Fast gridded scanning system can use the pattern matching algorithm to evaluate the structural defect by grid detector array.Firstly,the types and characteristics of common high-speed railway defects and highway geotechnical engineering structure defects are analyzed in detail,and the application of pattern matching method in civil engineering is also analyzed.In order to solve the problem of structure defects under high speed railway line,a three-dimensional finite element model of structure defects is set up.Batch processing is used to complete quick establishment of defect models,defect feature definition,dynamic analysis and response waveform processing.The establishment of defect model based on database,through the example analysis to determine the parameters of pattern matching method for structure defect detection by average response energy,predominant spectrum,predominant frequency of elastic wave.And through the combination of contrast sensitivity defects,determine the weighted values of the parameters.Based on the propagation characteristics of elastic wave,the matching weighted value matrix is set under different position combinations to improve the accuracy of matching.By analyzing the database waveform characteristics,considering the maximum matching error of the actual disease distribution,the threshold of the matching algorithm is determined to ensure the effectiveness of the matching results.The grided scanning detection method is used in Shanghai Hangzhou high-speed railway.At the same time,defect observation,optical fiber vibration testing and impact imaging method were carried out for the under structure of the suspected defects area of Shanghai Hongqiao station,aiming at CA mortar layer void evaluation.By comparing the results of the defect evaluation of the grid scanning and other detection methods,it is proved that the grid scanning method has good accuracy and effectiveness.Compared with the impact mapping method,the detection speed is improved by assembling the grid detector array,and the pattern matching method is combined with the grid distribution to improve the accuracy of disease detection.