Analysis of Buried Pipeline–Reverse Fault Interaction in Saturated Soil under Drained and Undrained Loading Conditions

Abstract Buried pipelines are vulnerable to permanent ground deformation from reverse faulting, yet their response in saturated conditions is not well understood. This study uses a validated three-dimensional finite-element model to investigate the behavior of buried steel pipelines subjected to reverse fault movement in saturated soils. The model simulates soil–pipeline interaction under both drained and undrained conditions, employing a modified Drucker–Prager Cap Plasticity model for the soil. A detailed parametric study evaluates the influence of fault offset, embedment depth, pipe thickness, and fault dip angle on pipeline performance. Key findings indicate that steeper fault angles (45°) and deeper embedment significantly increase pipe bending strains due to larger vertical displacements and greater soil confinement. Drained conditions were found to induce substantially higher strains than undrained conditions, which in turn were lower than those in dry soil. Undrained loading generated significant excess pore pressure, especially at shallower fault angles. Based on these results, the study proposes a novel predictive power–law relationship for estimating maximum bending strain as a function of a combined nondimensional soil–pipe interaction number ( ξ ). This formulation provides a practical tool for designing resilient pipeline systems in seismically active marine and terrestrial environments.