Estimation of buoyancy factor during inclined lateral breakout of on-bottom pipelines in clay

Publication Title
Estimation of buoyancy factor during inclined lateral breakout of on-bottom pipelines in clay

Abstract

Deepwater offshore pipelines are often laid directly on soft clayey seabed, without constructing a trench. The pipe gains partial embedment due to self-weight and stress concentration during installation. Consequently, heaves form at the ground surface surrounding the pipe. These heaves significantly influence the lateral resistance experienced by pipe during thermally-induced buckling. Direction of the pipe movement due to lateral buckling is dependent on its weight relative to the soil strength. Breakout resistance for pipe moving in different directions can be divided into two components - geotechnical resistance due to shear strength of the soil and buoyancy effect arising from the weight of displaced soil. Magnitude of this buoyancy effect enhances with the inclusion of surface heave. Literature expressed the buoyancy component as a product between weight of displaced soil and a buoyancy factor f_b. Researchers quantified f_b for pipe movement in both vertical and horizontal direction. Subsequently, it was also realized that f_b evolves with the direction of pipe movement, specifically due to the alteration in mobilized soil volume. A rigorous study to quantify the effect of surface heave on f_b for pipe movement in different direction is yet to be reported. This paper extensively investigates the influence of surface heave on the buoyancy component of breakout resistance of pipes moving in various directions. A series of large deformation finite element analyses are initially performed using Abaqus to capture the non-linearities associated with the problem geometry. Subsequently, the pipe is displaced in different directions till failure. Simulations are run with and without considering the soil unit weight. Obtained results are used to quantify the change in f_b with the change in direction of pipe movement. The findings from this study can be useful in precise estimation of breakout resistance of on-bottom pipelines for the design of controlled buckling.

Authors
Abhishek Ghosh Dastider; Santiram Chatterjee; Namburi Gowtham

Published In

21st International Conference on Soil Mechanics and Geotechnical Engineering (Vienna)

Theme

TC209

DOI
https://doi.org/10.53243/ICSMGE2026-1774

International Society for Soil Mechanics and Geotechnical Engineering

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