Experimental Research And Numerical Simulation Of Pipeline Dislocation Deformation Monitoring Based On OFDR

Pipeline is widely used in supply water supply,drainage,power supply,heating,gas supply and communication,and it plays an important role in national economic life.As the "lifeline" of a city,a system with real-time monitoring and early warning capability is of great significance.Traditional monitoring methods are difficult to ensure real-time and full-distributed pipeline monitoring.Distributed optical fiber sensing technology brings a new opportunity for economical,efficient and comprehensive real-time pipeline safety monitoring system.At present,the research of optical fiber monitoring of pipeline is mostly focused on qualitative monitoring.A few of studies focus on quantitatively monitoring of the continuous pipeline and few studies on quantitatively monitoring the pipeline damage and dislocation have been published.In this paper,the distributed optical fiber sensing technology is used to monitor the strain distribution of pipelines,and then the quantitative analysis of the dislocation after pipeline damage is performed.The following research work is mainly carried out:1.The optical frequency domain analysis technology is used as the experimental monitoring tool after the comparative analysis of a variety of distributed optical fiber sensing technologies.Two kind of layout methods and installation techniques of the sensing fiber for pipeline are determined after study,which are S-type comprehensive laying and fixed-point laying at the interface.2.An indoor experimental model box is carried out to monitor the deformation of the pipeline interface.In the experiment,two kinds of optical fiber layout schemes are used to test the bending of the pipeline under stress,the dislocation of segments condition,and the bending of the pipeline under stress under buried soil.The vertical deformation is measured by the percentile meter.The results show that the strain of the pipeline can be well monitored by the optical fiber monitoring.At the same time,aiming at finding out the influence of peak strain on the low sensing section of optical fibers near the free section,the influence of binder on the strain transfer characteristics of optical fibers was investigated experimentally.The results show that the binder has a slight influence on the low sensing section,but the influence range is not more than 12.5 cm,which does not affect the monitoring results of the tube body.Pipeline strain obtained by the distributed optical fiber monitoring is in agreement with the fiber and pipeline deformation.3.A method of calculating the vertical deformation of pipeline by using the average strain data at the pipe interface obtained from the free optical fiber between the fixed-point is proposed.Firstly,the deflection deformation of the pipeline is calculated by using the axial strain data of the optical fiber tube body.To verify the accuracy of the quantitative calculation of the optical fiber data.Assuming that the strain of the optical fibers is only caused by the vertical deformation,the staggered deformation of the nozzle can be estimated based on the average tensile strain data of the optical fibers at the fixed point of the interface.The calculated results are larger than the measured values of the percentile meter,and are generally close to the measured value.The results show the feasibility of quantitatively calculating the dislocation of pipeline interface deformation.4.By secondary development of MatDEM software,the coupling deformation model of threedimensional discrete element optical fiber and pipeline is established,and the optical fiber is modeled.The model is used to simulate various working conditions and optical fiber layout of indoor test.The results of numerical simulation are consistent with those of indoor test.In the simulation,the shape of fixed-point optical fibers data in four directions is consistent with the experimental results.The applicability and feasibility of discrete element numerical simulation for the study of discontinuity of pipeline interface are proved.The feasibility of using distributed optical fibers to quantitatively monitor pipeline deformation is proved by the comprehensive study of indoor test and numerical simulation,which provides a research idea for the future quantitative monitoring of pipeline deformation,especially the deformation of pipeline interface dislocation using distributed optical fibers.