Numerical Modelling of Buried Bended Elbow-Pipeline Subjected to Lateral Ground Displacements

This research investigates the soil-pipeline interaction in sand subjected to lateral ground displacements with emphasis on the peak forces exerted to a bended elbow-pipe. The purposes of this study are to reveal the behaviour of the buried elbow-pipe, where larger soil restraints are likely to occur on the elbow-region under sudden ground movements, and to improve the structural modelling. A series of three-dimensional (3-D) finite element (FE) analyses were performed to develop a design guideline of a buried elbow pipeline subjected to lateral ground loading. The investigations were conducted in both opening and closing modes of the elbow section for different initial pipe bending angles. Considerations were also given to the effects of pipe embedment depth, sand density and pipe-surface roughness. The pipeline was modelled by isotropic 3-D shell elements and the sand was modelled by 3-D solid continuum elements. To model the mechanical behavior of sands, Nor-Sand soil model was adopted. Results show that the opening mode exhibited higher ultimate forces and greater localised deformations when compared to the closing mode. Higher peak force values were computed when the pipe is deeper and the soil is denser. A non-dimensional chart that accounts for pipeline locations, bending angles and soil densities is developed. The observed soil failure mechanisms are also presented.