L52303 Development of Techniques to Assess the Long-Term Integrity of Wrinkled Pipeline

Abstract

The objective of the project was to develop a numerical model than may be used to predict the wrinkle formation and post formation behavior of a pipeline considering the effect of soil confinement and define the specifications for the development of a comprehensive wrinkle integrity assessment process. The result of this research is the development of wrinkle assessment techniques that could be used directly or could be used to codify maintenance guidelines. This project focused specifically on the pipe soil interaction modeling wrinkle formation as a result of the relative movement of the pipe and soil. The structural model developed and validated in this program and previous work could be applied to wrinkle bends, however, this issue is not specifically addressed in this report. In addition, the project development efforts focused on the monotonic soil interaction event of idealized (e.g., no secondary degradation like corrosion features) pipe segments. The project completed a critical review of existing structural and soil modelling techniques to identify the most suitable technologies for this application. The soil-pipe interaction under soil movement was found to be best represented using the LS-DYNA Multi-material Eulerian technique which permitted the application of a number of suitable soil constitutive models. This analysis tool permitted the consideration of a range of soil types and large soil displacements. Having defined the most suitable tool set, several pipe soil interaction models were developed. These models were used to illustrate the types of analyses that could be completed and the capabilities of the models to illustrate the sensitivity of the scenario loads, displacements to changes in soil, pipe and other parameters. The modeling results were discussed to demonstrate that their trends and results were in line with intuitive assumptions and engineering judgment. Additional models were developed to simulate large scale pipe-soil interaction laboratory test programs. The results of the simulated test programs were compared with the laboratory results as an initial validation of the modeling techniques and tools. The simulated soil displacement patterns, pipe strains and pipe displacement were shown to agree well with experimental results and as such illustrated the ability of the models to reproduce idealized pipe-soil interaction events. Full-scale soil displacement events were modeled to illustrate the application of the modeling tools to forecast or predict the effects of axial and transverse soil movements on buried pipeline segments. These results were used to illustrate the methods and assumptions inherent in the application of the modeling tools to predict soil loading on pipeline systems.