Research On Hole Grouting Defect Detection Based On Quasi Parallel Seismic Method

Grouting defects in prestressed concrete ducts are one of the common types of diseases in prestressed concrete bridges.How to detect grouting defects in prestressed ducts is currently a major research topic in the bridge industry.From the perspective of quasi parallel seismic method,this article proposes a theory based on Snell’s law on the variation of the first wave time with the position of sensor measurement points.The concept of maximum first wave delay time is proposed,and based on the theoretical research,a two-dimensional concrete model with grouting defects is established using ABAQUS finite element software.Through finite element simulation,the model size,defect size,and defect location are studied respectively The impact of various working conditions such as the diameter of the hitting ball and the material properties of the corrugated pipe on the detection of grouting defects in the corrugated pipe using parallel seismic method,and the innovative concept of defect comprehensive identification index has been proposed.Finally,the quasi parallel seismic method was applied to the detection experiment of a concrete model with grouting defects in the interior,successfully detecting the grouting defects in the structure and locating the specific locations of the defects.The research results show that:(1)The two-dimensional concrete model with grouting defects in ducts established through ABAQUS finite element software can be used to study the detection of grouting defect positions in corrugated pipes using parallel seismic methods.The propagation and attenuation laws of sound waves in this model and the detected defect positions are basically consistent with the actual situation;(2)In the finite element simulation process,by corresponding the waveform to the corresponding sensor measurement point position,and changing the defect arrangement inside the corrugated pipe,the waveform changes caused by different defects can be obtained.By comparing the differences,the law of waveform changes caused by defect changes can be analyzed and found;(3)Based on Snell’s law,by analyzing the variation law of the first wave time of sound waves in concrete structures,the arrangement positions of sensor measurement points are divided into zones,and the calculation formula for the relationship between the first wave time and measurement point positions in different measurement areas is obtained.At the same time,the concept of maximum first wave delay time was proposed,and through theoretical calculation analysis,the theoretical calculation position of the maximum first wave delay time was obtained.Subsequently,through finite element simulation and experimental research,the actual measurement positions of the maximum first wave delay time obtained were compared with the theoretical calculation positions,verifying the theoretical rationality of the maximum first wave delay time;(4)During the simulation process,the concept of delayed detection distance was proposed to make defect localization more accurate.By proposing a new comprehensive defect identification index,three analysis indicators are weighted to reduce the error of each indicator in the simulation process,improve the reliability of the simulation,and provide reference for practical experiments;(5)Through experimental research,various indicators of the acoustic signal were analyzed using the defect comprehensive identification index.The calculated defect location was basically consistent with the actual defect location.The calculated defect comprehensive identification index was processed using 3D cloud images using 3ds Max software,which can more intuitively detect the location of defects;(6)For the experimental process,this article proposes an optimized tapping scheme to make the excitation more precise.At the same time,by setting up a control group of sensor measurement points and normalizing the acoustic signals of other sensor measurement points,the error caused by the excitation signal is reduced.On this basis,the defect positions obtained through experimental detection are basically consistent with the actual designed defect positions,proving the feasibility of this method.In summary,the quasi parallel seismic method has been preliminarily applied in detecting grouting defects in concrete corrugated pipes.With the gradual deepening of research,the quasi parallel seismic method can provide an effective tool for the field of grouting defect detection in concrete corrugated pipes.The thesis has 98 pictures,16 tables and 84 references.