Study On Damage Detection Monitoring Method Based On Dynamic Distributed Strain Of Submarine Pipeline

Leakage of submarine pipelines will cause irreversible damage to production and life of the nation.Monitoring the health of submarine pipelines takes much time at present and cannot be carried out in real time.However,the distributed fiber sensor can overcome that problem.The chief application of the sensor now is monitoring temperatures of submarine pipelines,while studies and applications of the sensor are few.The new monitoring of AT-BOTDA theory dynamic strain provides a new way for health monitoring based on submarine pipelines strains.First of all,in order to study distributive monitoring methods of damage detection in submarine pipelines,this article bases on the concept of scalar transmissibility and puts forward the concept of strain transmissibility and relevant methods of damage detection to recognize the damage in submarine pipelines.Moreover,this article uses the finite element model to verify the methods.In this article,variant damage degrees in pipeline models are analyzed.Through comparison,it is discovered that those methods are more sensitive than acceleration transmissibility and theory transmissibility.Analysis of boundary conditions finds that by using those methods the detection of damage sites is not affected by boundary conditions.The choice of reference modulus is analyzed and it is validated that reference modulus should be chosen from the undamaged positions away from the inflexion point.The methods can be applied effectively to detecting damage in submarine pipelines,and thus lay the foundation of applying distributive sensors to monitoring the health of submarine pipelines.Next,this article designs submarine pipeline models based on hydro-elasticity similarity,introduces AT-BOTDA theory,and applies the distributed fiber sensor and the strain gauge to monitor submarine pipeline models in Seismic wave flow joint simulation test system.Strain data are analyzed through designing 15 conditions including damaged ones and undamaged ones.Moreover,the proposed damage detection method is verified and analyzed.The experiment indicates the following findings.First,vibration of submarine pipelines is mainly forces vibration.Second,in the AT-BOTDA model,data acquired by the distributed fiber sensor is of certain precision yet not precise enough for recognize small strains.Third,distributed fiber sensor can recognize influence of wave heights,span heights and flow velocities on strains of submarine pipeline.Forth,the proposed damage detection method in this article can be applied effectively to model tests of submarine pipelines.