Research On Key Technologies Of Detection And Location Of Shallow-buried Pipeline

It is a common engineering technology to repair shallow-buried leaking oil pipelines through the cofferdam work.Due to the limitation of current technology by which cofferdam work cannot locate the pipelines accurately,it is invalid to narrow the scope of operation,which also causes more maintenance cost and accident risk.In order to realize the intelligence and automation of this kind of cofferdam work,it is essential that accurately locating the cross-section circle from radial direction of the pipes.In the case of temporary shortage of special research at home and abroad,this thesis focused on a systematic declaration of detection technology on buried pipelines used frequently in ocean acoustics.It first spotlighted the acoustic model of buried pipeline detection,combined by practice in repairing work of shallow-buried oil pipelines and analyzed attenuation characteristic when sonic wave was in the shallow medium,which provided considerable theoretical basis for acoustic detection methodology.Then,based on the highlight model and geometric sound ray method,it established the pipeline echo model and geometric model of location of pipeline cross-section circle.Through the simulation and water tank experiment,it verified the effectiveness of the model above,based on which the algorithm of center-point locating calculation was put forward after the least-square-revised objective function was built.Adapted this approach,the locating calculation to center-point is reliable and accurate with the maximum error of 0.02 meters and average error of below 0.01 meters,which satisfied the basic requirement of engineering and could serve as a theoretical reference for the pipeline cross-section circle locating methodology when buried in shallows.In the end,the thesis introduced a four-channel sonar launching and receiving platform set up in both software and hardware environments.First,it referred to several system hardware module design including DDS signal generating circuit,power amplifying circuit,power supply system,energy storage circuit,echo isolation,gating,voltage-control amplifying and FPGA master control module,etc.Second,it described the working process of the system software design including FPGA program,upper computer LabVIEW program and so on through state transition diagram and flow chart.Last,it debugged and confirmed the detection system mentioned in this project.