Used to convey oil and gas from offshore fields to onshore facilities, offshore pipes are a safe, effective, and swift means of transporting fuel, usually laid directly on the ocean floor bed or buried at a particular depth. Pipes are usually coated with a concrete layer to increase their stability and to protect from external forces. The high temperatures required for oil and gas transport can cause thermal expansion in the pipes, and eventually result in buckling; either upheaval buckling, on the vertical plane, or lateral bucking on the horizontal plane.
A new paper in the Journal of Pipelines Systems Engineering and Practice looks at the pipe-soil interaction, specific to buckling. The study by authors Prem Kumar; Debtanu Seth; Bappaditya Manna, M.ASCE; and J. T. Shahu seeks to understand both the uplift and lateral capacity of pipes buried in homogeneous soft clay seabed.
Their research entitled “Lateral and Uplift Capacity of Pipeline Buried in Seabed of Homogeneous Clay” examines the behavior of failure mechanisms, and the capacity factors during uplift and lateral displacement of the pipeline. Additionally, they compared the uplift and lateral capacity factors to find out the most vulnerable orientation toward which the pipe may buckle.
Learn more in the abstract below, or by reading the full paper in the ASCE Library: https://doi.org/10.1061/(ASCE)PS.1949-1204.0000566
Abstract
Buried offshore pipes are prone to upheaval and lateral buckling because of the high temperature and pressure of the materials being transported. An attempt has been made in the present study to evaluate uplift and lateral capacity of buried offshore pipes in a soft clay seabed using finite-element software. The numerical model used in the present study has been validated against results available in the literature. Finite-element analyses are carried out to study the upheaval and lateral buckling behavior of pipes for both the no-tension (NT) condition, i.e., when separation occurs between the pipe and soil, and the full-tension (FT) condition, i.e., when the soil beneath the pipe remains attached to the pipe. The variation of both uplift and lateral normalized capacity factors with soil cover depth ratio is presented for different combinations of soil strength and effective weight. Both uplift and lateral capacity factors have been found to increase and reach a constant peak value with increasing depth of soil cover. A transition from global and local failure mechanisms of a pipe is observed when the capacity factors attain their peak values at a limiting soil cover depth. The critical cases for the design of buried offshore pipe in homogeneous clay are established for both NT and FT conditions.
Read the full paper in the ASCE Library: https://doi.org/10.1061/(ASCE)PS.1949-1204.0000566
