Offshore oil and gas pipelines are commonly buried below the seabed to provide environmental stability and protection. Many of these pipelines are prone to upheaval buckling following burial. Trench backfill provides restraint for these pipelines to resist the associated uplift forces. Soil failure mechanisms can extend to the surface (shallow) or remain localised within the soil body (deep); the exact conditions that cause this transition are currently unclear. A parametric study of pipeline uplift in clays has been conducted using finite element analysis. The results indicate that uplift factors and failure mechanisms for pipelines are similar to those found for plate anchors, with comparable uplift capacities approximately 4 to 6 % greater for the pipelines.
There is extensive use of buried pipelines within the offshore oil and gas industries to transport hydrocarbons from their point of recovery to the shore (or to other installations). Burial of these pipelines beneath the seabed is necessary for safety, operational and environmental concerns, e.g. prevention of damage to fishing vessels, on bottom stability and for the improvement of the thermal properties of the pipeline system. Since pipelines are laid in remote and potentially hostile environments, the cost of laying the pipe can be extremely high. Likewise the cost of any repairs or remediation work is equally high, in terms of the actual work required, equipment mobilisation times and costs, and reduced output. Therefore, offshore buried pipelines must be constructed as quickly and efficiently as possible, whilst maintaining the highest level of certainty against failure for the duration of their use. To achieve high flow rates in pipelines, the gas or oil must be kept at high temperature and pressure. Normally, these pipelines are laid with near zero axial loads, at the ambient temperature.