Improved Design Guidelines for Pipelines Subjected to Vertical Fault Movement in Dry Sand

Practicing engineers use the uncertain bilinear soil spring methodology recommended by engineering guidelines to predict soil loads acting on buried pipelines. Even though more advanced solutions are available in the literature to address these uncertainties, they cannot be practically implemented owing to various industry constraints such as computational and modeling costs. This paper proposes a fitting expression that can enable practicing engineers to produce safer, more reliable outcomes at no additional cost. The proposed expression is based on a calibrated advanced finite-element (FE) model featuring an advanced user-defined Nor-Sand (NS) soil model, and the simplistic Mohr-Coulomb (MC) soil model, which is commonly used in the industry for numerical modeling. The developed FE model was first validated by comparing the upward and peak dimensionless soil forces computed with those predicted by engineering guidelines and other analytical models reported in the literature. A series of FE analyses were then performed using our calibrated FE model incorporating the advanced NS soil model to simulate buried pipe response under downward displacement, which was not realistically captured either with the MC soil model or available engineering guidelines. Results of the analyses were used to derive a fitting expression for predicting the resistance to downward pipeline displacement to address what is lacking in the current industry practice. The developed tool contributes to the design and analysis of buried pipelines by enabling practicing engineers to produce safer, more reliable outcomes.