Yield Envelopes for Oblique Pipeline/Soil Interaction Events
An understanding of the soil load and restraint on pipelines due to relative pipeline/soil movement is required to assess the pipeline mechanical response that may affect pipeline serviceability or integrity. Current engineering practice for pipeline/soil interaction is based on idealized structural-based numerical models that evaluate pipeline mechanical response using beam elements and soil behavior using discrete spring system. The soil spring are characterized by independent load- displacement relationships for only principal directions (i.e. longitudinal, later horizontal, vertical upward and vertical downward). Recent studies have indicated that for complex relative pipeline/soil movement (e.g. axiallateral interaction) using discrete spring system may not be valid. There is a need for more advanced numerical tools and engineering guidelines to assess the pipeline's response in comple loading conditions and reduce model uncertainty. This project will investigate complex soil failure processes and load transfer mechanisms during nonlinear, oblique pipeline/soil interaction events associated with long-term permanent ground deformations. Parametric analysis will be conducted using continuum finite element methods with the software package ABAQUS. The numerical models will be calibrated with available physical data and some complementary centrifuge tests conducted during this study. Interaction diagrams that characterize the coupled soil load-displacement mechanisms will be developed. Alternative soil spring formulations that account for coupled soil deformation mechanisms during oblique pipeline/soil interaction events will be proposed based on interaction diagrams. The effects of this alternative soil spring formulation on pipelines responses via structural finite element model will be assessed.
