Study On Integrity Assessment Of Buried Bell-and-spigot Pipelines Under The Effect Of Erosion Voids

The randomness of time and space is typical of the emergence of erosion void, which makes it hard for the traditional discrete type sensor to monitor the appearance and development of erosion void which is near to the buried pipeline, the advantages of distributed optical fiber sensor offer the possibility for such a distributed monitoring. However, due to the self-limitation of distributed optical fiber, it cannot monitor the joint of pipeline effectively, but the method of inversion of finite element analysis can make up for the deficiency. On the basis of the above ideas, build a integrity assessment of buried bell-and-spigot pipelines under the effect of erosion voids by use of distributed strain monitoring data and three-dimensional finite element model of pipeline simultaneously and design a variety of optical fiber measurement joint deformation device. The following work has been achieved in the paper:1) Based on the ANSYS finite element analysis software, establish a three-dimensional finite element model of pipe under the effect of erosion voids by using super elastic unit, highly nonlinear analysis such as soil elastic-plastic analysis, contact analysis of joint and rubber sealing ring, pipe-soil contact analysis and life and death unit technology, which includes bell-and-spigot joint. Analyze the action of buried pipeline structural response and failure mechanism by calculating the different shape and position of erosion void, the pipe body pressure, soil heights and so on.2) Put forward a integrity assessment of buried pipelines which bases on the distributed optical fiber monitoring and three-dimensional nonlinear finite element analysis when erosion voids affect buried bell-and-spigot pipelines.Through the full size of buried pipelines monitoring test under the effect of erosion void, use distributed optical fiber sensor to monitor longitudinal strain of pipeline; secondly, based on the buried pipeline and its environment, and fix the bell-and-spigot joint type buried pipeline model by the method of monitoring data and manual adjustment; and obtain stress strain of the joint and the remaining load ability of pipeline by finite element analysis subsequently; finally, evaluate the integrity of the bell-and-spigot joint type buried pipeline by the comprehensive utilization of the above methods. The method not only solves the problem of distributed strain monitoring technology to measure the stress and deformation of joint, but also overcomes the limitations of numerical model to accurately simulating the actual buried pipeline structure state, which provides a scientific basis for the buried pipe structure state degradation assessment and remaining life prediction.3) In order to make up for the inadequacy of fiber optic monitoring joint, design a variety of optical fiber measurement joint deformation device and monitoring methods, several deformation device model test indicate the feasibility of measuring way and the validity of measuring result. It provides a certain using and design thinking of distributed optical fiber for monitoring pipeline in future.