Leakage Detection And Location Of Buried Pressure Pipeline Based On Solid Acoustic Wave

Buried pressure pipeline leakage has become one of the great threats to pipeline.The solid acoustic method is one of the most potential methods in leak detection and leak location.However,the method suffers from a number of problems such as insufficient generalisation of the data model,difficulty in obtaining key parameters accurately,and the absence of a complete sensor selection method.The research on the mechanism of the leakage acoustic field can help to improve the solid acoustic wave-based leakage detection method.On this basis,this paper firstly carried out the research on the mechanism of leak-induced solid acoustic waves.Driven by this,the methods of leak detection and location based on point sensors and distributed optical fibers has been significantly enhanced.In the mechanistic study,the leakage sound field is divided into source and propagation.Leak source studies focus on the three properties of leak rate,initial acoustic intensity in the pipe wall and initial acoustic intensity in the soil,which are of most interest in leak detection.This paper proposes a numerical simulation method that includes fluid,pipe wall and soil models to solve the leak source properties.In this method,the fluid model is firstly used to obtain the leakage rate,the simplified load in the pipe wall and the simplified load in the soil,and then the simplified loads are applied to the pipe wall model and the soil model to obtain the initial acoustic intensity in the pipe wall and the soil.Through this method,the effects of pipe diameter,pipe internal pressure,leakage pore size,particle size and porosity of the soil outside the pipe on the characteristics of the three leakage sources are investigated,which allows the leakage source mechanism to be studied from the perspective of key characteristics.The proposed method has also been used to establish quantitative relationships between leak conditions,leak rate and initial acoustic intensity,and to calculate the values of the three characteristics for common operating conditions.The quantitative relationship provides a key basis for the selection of sensors and the determination of sensor arrangements for different operating conditions and different detectable leak rates.In addition,a sound source calibration experiment is carried out to validate the results of the numerical simulation method.In the propagation study,the three characteristics of wave velocity propagating along the pipe wall,attenuation propagating along the pipe wall and attenuation propagating along the soil are used as the starting point.This paper investigates the wave velocity and attenuation characteristics for leak detection from both theoretical solution and experimental calibration.For the theoretical solution of the wave velocity propagating along the pipe wall,a new low-frequency simplified dispersion equation method is proposed,which has the advantages of both the local volume wave superposition method and the low-frequency approximate solution method.The method describes the pipe wall by local volume waves and uses low-frequency simplified loading to describe the effects of fluids and soils.The method can be used to obtain the wave velocities propagating along the pipe wall of the three low-frequency modes T(0,1),L(0,1)and F(1,1),which are most needed for leak detection.For the propagation attenuation,this paper uses a uniform exponential form to express the attenuation along pipe walls and in soils.In terms of experimental calibration,a fast and accurate experiment method and signal processing method are proposed for the three propagation characteristics.The experimental calibration verifies the validity of the theoretical solution and also provides the material attenuation coefficients in the attenuation theory formulation.The leakage field mechanism are used to improve leak identification and localisation methods based on point sensors and distributed fibres.In the study of leak identification and localisation based on point sensors,the paper first solves for the sound field of leaks in the pipe wall by the leak mechanism,which leads to the determination of the type and arrangement of the point sensors.This paper then improves the leak identification and localisation algorithm.Based on the proposed modal separation method,a theoretical model and a data model are combined to improve leak identification.The modal separation method and the theoretical calculation method of the wave velocity propagating along the pipe wall are used to improve the accuracy of the leak localisation.In the study of leak identification and localisation based on distributed optical fibres,this paper first calculates the intensity distribution of leak acoustic waves in the soil by the combination of the initial acoustic wave intensity and the soil attenuation.This distribution is used to determine the fibre arrangement.Then,this paper makes full use of the spatio-temporal characteristics of the optical fibre signal to improve the accuracy and speed of leak detection.The two leak detection methods based on the random forest model and the Faster R-CNN model are proposed.The Faster R-CNN model-based method has high recognition rate,low false alarm rate and high processing speed,which can identify and locate leak events from the massive urban distributed fibre optic signals.Finally,the research results are summarized,and the future research directions are prospected.