Pipeline systems are integral components of the system infrastructure forthe transport of hydrocarbon resources. In arctic and harsh environments, thesepipelines may be subject to large deformation geohazards. Pipeline/soilinteraction events are often examined using a structural pipe/spring model. This approach does not account for more realistic soil constitutive behaviour, soil deformation mechanisms and effects of soil load transfer on pipelinemechanical response. This paper examines pipe/soil interaction events duringoblique lateral-vertical soil movements using plane strain finite elementanalysis. The results from this study provide a technical framework to assessthe effects of geotechnical loads on buried pipelines, highlight key parametersinfluencing soil yield envelopes, and identify soil failure mechanisms foroblique pipe/soil interaction events that can be used in the design of buriedpipelines for large deformation geohazards. The results may be used tobenchmark more complex loading events, such as coupled ice keel/seabed/pipelineinteraction, that has limited physical basis for validation.
Current engineering practice recommends the use of structural beam/springmodels to simulate pipeline/soil interaction events for the prediction ofpipeline mechanical response (e.g. ALA, 2002; Honegger and Nyman, 2004). The" continuum" soil behaviour is idealised by a series of discrete, independent, orthogonal springs representing the distributed mechanical response along theaxial, lateral and vertical pipe axes. The soil spring load-displacementrelationship is generally defined by bilinear or hyperbolic expressions as afunction of the peak load and displacement at peak load. For large deformationground movement events; such as ice gouging or seismic fault movement, recentstudies indicate the structural models are deficient and do not account for thecomplex response including load coupling and superposition errors (Daiyan etal., 2010a; Peek and Nobahar, 2012; Phillips et al., 2004a). There is a need toevaluate the current state of practice for the numerical modelling ofpipeline/soil interaction events with respect to the simulation of morerealistic soil behaviour and complex loading events; such as obliquepipeline/soil interaction.
Pipeline/soil interaction is a multifaceted problem that involves theinterplay between factors including the magnitude and distribution of soilproperties (e.g. type, unit weight, strength parameters, constitutiverelationships, rate sensitivity), contact mechanics (e.g. interface properties)pipeline characteristics (e.g. diameter, burial depth) and load effects (e.g.oblique coupling, strain localization, discontinuous behaviour). This drivesthe development of a robust and comprehensive technical framework includinglaboratory tests to refine soil constitutive models and physical models tovalidate advanced computational models in support of engineering analysis anddesign activities (Kenny et al., 2007; Pike and Kenny, 2011, 2012).