Numerical investigation of soil–pipeline system behavior nearby unsupported excavation in saturated and unsaturated glacial till

Abstract

Buried pipeline systems form vital infrastructure, all over the world, to transport resources such as water, oil, and gas from the production stage to the locations of consumption. Failure or rupture in pipelines in general and oil or gas pipelines in particular lead to not only economic losses that are expensive, but also cause extensive damage to the environment in several scenarios. One of the key reasons for buried pipeline systems failure is associated with excavation or soil trenching within the proximity of pipelines. Soil deformation associated with excavation causes relative displacement between the pipeline and the surrounding soil, which contributes to external as well as internal stresses and strains on the pipelines. In this study, numerical analyses are carried out to investigate the behaviors of buried rigid and flexible pipelines by extending the effective stress analysis and the modified effective stress analysis approaches for saturated and unsaturated soils, respectively. The pipe displacement, strains, and internal force results from the study suggest that soil trenching in unsaturated soils contribute to limited deformations within the proximity of the embedded pipelines and result in lower internal forces. The proposed methodology can be used to determine the safe depths of unsupported excavations in unsaturated soils without causing excessive strains or internal forces in the ring of rigid and flexible pipes.