How to Design Geohazard Resistant Steel Pipe in Critical Fault Crossing Areas

The paper investigates the structural performance and design of large-diameter continuous (welded) buried steel pipelines in seismic fault crossings, which constitute a potential threat to their structural integrity. The buried pipeline should be able to accommodate ground-induced deformations, absorbing the ground-induced deformation in an efficient manner and sustaining the tensile and compressive strains that develop in the pipe wall. The problem is investigated numerically using advanced finite elements, which simulate the steel pipe, the soil, and the soil-pipe interface in a rigorous manner. Results are obtained for two cases, both referring to actual applications in North America: an 84-in. pipeline crossing a 6.55-ft-displacement strike-slip fault and a 108-in. pipeline crossing a 12.2-ft-displacement normal fault. The results show that large-diameter steel welded pipelines, properly designed through a strain-based design procedure, can sustain ground-induced actions from fault movement, while maintaining their operational function. The introduction of the Geohazard Resilient Steel Pipe (GRSP) concept, a novel patented system consisting of a series of pipe wall projections at appropriate locations along the pipeline within the fault zone, assists the pipeline in absorbing the imposed ground-induced deformation, reduces pipeline distress, increases pipeline performance, and constitutes an efficient tool for increasing pipeline safety in seismic fault crossings.