Research On Grouting Compactness Detection Of Prestressed Pipeline Based On Ultrasonic Transmission Method

In recent years,with the rapid development of highway bridge construction in China,post-tensioned concrete beams are widely used in bridge system construction,and prestressed concrete Bridges occupy the vast majority of newly-built Bridges in China.The prestressed grouted corrugated pipe is an important part of the concrete bridge.The uncompactness of the grouted corrugated pipe will lead to the loss or even loss of the prestress of the bridge,which will lead to the crack or even collapse of the bridge.Therefore,the detection of the compactness of the prestressed grouting bellows is particularly important to ensure the grouting quality of the prestressed pipe.Based on the ultrasonic transmission method combined with the test beam,this paper conducted the compactness detection of the prestressed grouting bellows,and carried out the following research work:1.The research background and the significance of the topic are introduced in detail,and the NDT methods are investigated and analyzed at home and abroad,and the ultrasonic transmission method is chosen as the NDT method in this paper.2.The emphasis of the combination of ultrasonic transmission testing design and production of a batch of ideal experimental beams for the whole of the bellows compactness testing analysis,some conclusions are:(1)the global compactness of grouting bellows debuted with the ultrasonic transmission wave has a linear relationship,with the increase of grouting pipe compactness,ultrasonic transmission in the first wave velocity decreased gradually;(2)The detection method of positive and negative transmission has little effect on the transmitted first wave velocity,and the length of bellows has little effect on the transmitted first wave velocity,which indicates that the linear relationship between the compactness and the first wave velocity based on the ultrasonic transmission method for measuring the global compactness of the grouted pipeline is general.(3)The one-dimensional equivalent model of the grouted bellows combined with the theoretical analysis of the first-wave slowness has a reference significance for the detection of the compactness of the grouted pipes.With the increase of the compactness of the grouted pipes,the first-wave slowness value gradually increases,but the measured value of the first-wave slowness is slightly higher than the theoretical value of the first-wave slowness.(4)There is a linear relationship between the compactness of the grouting bellows and the dominant frequency and amplitude of the ultrasonic transmission.With the increase of the compactness of the grouting bellows,the dominant frequency and amplitude of the ultrasonic transmission decrease gradually.(5)The weight analysis based on entropy weight method shows that:ultrasonic transmission first wave velocity,transmission dominant frequency and dominant frequency amplitude have the same characterization of density change,and they can all be used to determine the compacting bellows’ density detection;(6)The research on defect probability discrimination based on normal distribution and T distribution shows that both of these two methods can be used for global compactness classification discrimination,but the defect probability discrimination based on T distribution has a good effect in small sample discrimination.3.The convolutional neural network(CNN)model is used to classify and learn the different grouting compactness data under different preprocessing.The results show that CNN can be used for fast classification and recognition of grouting pipeline compactness,and the wavelet time-frequency transform processing of transmission data has a better recognition effect than the filtering and Fourier transform processing.