Safety Monitoring Method Of Buried Pipeline Based On Distributed Optical Fiber Sensing Technology And Vibration Load Identification

As the lifeline of energy transmission,long-distance buried pipelines are an important foundation for my country's economic construction and development.However,when it passes through seismic fault zones,coal mine goafs,and landslides,it is very susceptible to be destroyed by natural geological disasters such as rockfall impacts and debris flows,and longterm vehicle load and heavy load occupation will cause fatigue damage.Therefore,the safety monitoring of long-distance buried pipelines is of great significance to improve the safe service period of pipelines.Long-distance buried pipelines in depopulated zone such as mountains and plains are generally unmanned on-site monitoring and cannot identify the type of load acting on it.It also becomes a problem for pipeline safety monitoring.Distributed optical fiber vibration sensing technology has the advantages of anti-electromagnetic interference,heatresistance,and long-distance monitoring.It can be layed near the long-distance buried pipelines for real-time monitoring,and can record and save vibration data of different load effects.Aiming at the problem of how to identify the load types acting on long-distance buried pipelines,this paper proposes a method for vibration monitoring of buried pipelines based on the load identification of distributed optical fiber vibration sensing technology(?-otdr).Through experimental and theoretical analysis,the feasibility of this method was verified,and combined with finite element analysis,simulating the vibration process of the pipeline in the depopulated zone under the impact load of rockfall.The research results are as follows:1.Introduce the principle of distributed optical fiber vibration sensing based on ?-otdr,and summarize the research status at home and abroad.According to the current research progress and level,a load identification method for buried pipelines based on distributed optical fiber vibration sensing monitoring system is proposed.2.Research on the induction performance test of distributed optical fiber vibration sensor,and conducting experiment with different types of vibration sensors and different stress-state vibration sensors to judge the difference of different stress and different types of optical fibers under the same vibration.The experimental results show that: in actual engineering,proper prestressing on the optical fiber can improve the sensitivity of sensors.By comparing the vibration images of bare fiber,white tube fiber and yellow tube fiber,it is found that the vibration intensity of the three is almost irregular,and the small difference means that the protective layer has little effect on the vibration of the optical fiber and mainly plays a protective role.3.Research on the load identification method based on the distributed optical fiber vibration sensing technology.In the field experiment,the distributed optical fiber sensor and the acceleration sensor were simultaneously arranged near the buried pipeline,and the monitored data was drawed as the time-history diagrams and 3D vibration diagram for comparison.By comparing the time-history diagrams of the distributed vibration sensing system and the acceleration sensing system,it comes to a conclusion that the trend of the signals monitored by the two sensors change with time is basically consistent,which proves the accuracy of the distributed optical fiber vibration sensing monitoring system.To further verify the feasibility of distributed optical fiber sensor safety monitoring technology,the relationship between load quality and signal was studied and the experimental results show that the distributed optical fiber sensor and acceleration sensor alomost have the same trend in the signal-load curves,indicating that distributed fiber load identification method has certain accuracy.4.The part of finite element mainly analyzes and deals with the mechanical state of the pipeline under several load conditions by ABAQUS for numerical simulation of buried pipeline in the unmanned area under rock-fall impacts.And comparing the time-history diagrams of the two sensors' vibration signal with the time-history diagrams of strain energy by FEM.It is found that the data of the signal intensity time history collected by the sensors and the pipeline strain energy by finite element numerical simulation have a certain degree of fluctuation properties.It further shows that vibration monitoring of pipeline can effectively replace strain monitoring of pipeline.Finally,according to the identified working conditions,the damage theory combined with the reliability method is used to conduct a preliminary theoretical discussion on the remaining life of the pipeline.