Numerical Stress-Strain Analysis of Buried Steel Pipelines Crossing Active Strike-Slip Faults with an Emphasis on Fault Modeling Aspects

At present, advanced numerical models of pipelines crossing active faults are based on the representation of the pipeline as an ensemble of shell or solid finite elements. The surrounding soil is represented as an inelastic continuum using appropriate constitutive models and three-dimensional (3D) solid elements. The pipeline-soil interaction is modeled as a surface-to-surface contact problem. These models allow a detailed analysis of the stress-strain state with account for localized limit states to be performed. Still, concerning the lack of data from real seismic events and large-scale tests, which can be used for calibration of numerical models, the question of adequacy of the numerical results is a topical issue. In this paper, a 3D numerical model of a buried steel pipeline crossing an active tectonic fault is developed and discussed with an emphasis on the pipeline-soil interaction and mathematical representation of the fault. The influence of the fault model on the predicted stress-strain state of the pipeline is analyzed using two different types of fault representation. The first approach is based on the continuous representation of the fault; in the second approach, two separate soil blocks interacting along the fault plane are introduced. The latter approach has not yet been applied to the analysis of fault-crossing problems. The numerical results are compared on the basis of displacement, strain and contact soil pressure distributions, evolution of the pipe ovalization parameter and bending moment in the critical cross section, and soil deformations in the near-fault zone.