Experiment Study On Leakage Monitoring Of Fabricated Pipe Gallery Joint Based On Piezoelectric Impedance

Due to its advantages of high sensitivity,simple operation and low cost,piezoelectric impedance technology has been widely used in the field of structural health monitoring.In this thesis,the piezoelectric impedance method is applied to monitoring the leakage of underground pipe gallery joint.The leakage monitoring experiments were carried out on the scale pipe gallery and the steel plate joint model which simulated the pipe gallery joint structure.The main research results are as follows:(1)Experimental study on leakage monitoring of steel plate joints based on piezoelectric impedance was carried out.In this study,under the condition of no water pressure,the piezoelectric impedance can accurately identify the change of water volume on the surface of steel plate.Under the condition of water pressure,the piezoelectric impedance can accurately identify the change of water pressure inside the joint.The experimental results show that it is feasible to use the piezoelectric impedance method to monitor water leakage.(2)Exploring the identification effect of different frequency bands on the leakage of the scaled pipe gallery joint.The impedance analyzer was used to measure the real admittance curve of the PZT at different frequency bands,and the RMSD index and MD index of each frequency band were calculated.The research shows that the best frequency band for leakage monitoring is 0-500 kHz.(3)Exploring the change of the admittance curve of PZT when immersion in water.In this study,the PZT was directly immersed in water,by changing the water volume and the immersion time,the change of the admittance curve of each PZT was monitored,and the corresponding RMSD and MD indexes were calculated.The results show that with the increase of water volume and immersion time,the admittance curve will move upward as a whole,and the real admittance curve changes more obviously and regularly than the imaginary admittance curve,the RMSD index and MD index of the real admittance curve increases continuously.It is shown that when the leakage contacts with the PZT directly,the piezoelectric impedance method can be used to accurately identify the situation of PZT immersion.(4)Under the condition of water pressure,experimental study on leakage monitoring of the scaled pipe gallery joint based on the piezoelectric impedance was carried out.In this study,PZT sensors were attached near the joint and different initial water pressures were set.By monitoring the changes of the real admittance curve of each PZT under different initial water pressure,and calculating the corresponding RMSD and MD index,it shows that when the water pressure change is greater than 7kPa,the piezoelectric impedance method can correctly identify the water pressure change,that is,it can identify the leakage at this time.