At the upcoming Offshore Pipeline Technology Conference (OPT 2016) in Amsterdam, our senior project engineer Charles de Brier will present a paper discussing the added value of advanced interface shear testing for pipeline walking propensity.

Abstract: On the Added Value of Advanced Interface Shear Testing for Pipeline Walking Mitigation

Charles de Brier, Jean-Christophe Ballard, Fugro GeoConsulting
David Colliard, Total S.A.

It is important to use specific laboratory testing devices to measure accurately the pipeline-soil interface shear strength at the velocities and contact stresses relevant to pipelines. This paper will first describe a new torsional shear device equipment that is capable of monotonic and cyclic testing at low stress level and for a wide range of velocities with cumulative shearing distance only limited by a specified test duration. The paper will then present results of tests obtained on soft clay samples collected offshore West Africa and discuss the main observations from those tests in the light of the new theoretical framework for axial pipe-soil interaction that is emerging. Those results will also be compared with data obtained with other laboratory testing devices and in situ pipe model test data from the same site. Finally, results of finite element simulations will be presented to demonstrate the added value this type of testing can have on pipeline walking propensity and required stabilisation measures.

At OMAE2015 in St. John’s (CAN), Prigiarto Hokkal Yonatan presented a paper introducing a new technique to assess the risk of upheaval buckling (UHB). This new methodology uses a backfill soil spring (BFSS) attached to the top of the pipe for representing the uplift resistance provided by the backfill soil on top of a buried pipeline. This tool will be available in the brand new SAGE Profile 3.0 to be released in the summer of this year!

Abstract: Numerical Simulation Of Upheaval Buckling Using Intelligent Backfill Soil Spring.

Prigiarto Hokkal Yonatan, Filip Van den Abeele and Jean-Christophe Ballard, Fugro GeoConsulting Belgium

Designing the cover height of buried pipelines to prevent them from buckling requires a method that can thoroughly and realistically model the phenomenon. This paper introduces a new technique to assess the risk of upheaval buckling (UHB) by using backfill soil springs (BFSS) to represent the uplift resistance provided by the backfill soil on top of a buried pipeline. This paper investigates the pre-buckling pipeline behavior related to UHB and highlights some of the key parameters governing the analysis. UHB assessment based on a case study was carried out and the results were then compared with those obtained from force-equilibrium methods generally used in the industry. The comparison shows that UHB assessment can be performed more rigorous using BFSS than using force-equilibrium methods. Therefore, using BFSS for UHB assessment improve the reliability in cover height design.

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At the 10th edition of the International Pipeline Conference (IPC2014), our senior pipeline consultant Filip Van den Abeele will present a paper on structural reliability of free spanning pipelines. The paper covers a risk based evaluation of free spans, by applying the principles of structural reliability theory to the problem of long free spanning pipelines subjected to vortex induced vibrations.

Abstract: Structural Reliability of Free Spanning Pipelines

Filip Van den Abeele, Frédérique Boël and Jean-François Vanden Berghe, Fugro GeoConsulting Belgium

When installing subsea pipelines on an uneven seabed, the free spans can be vulnerable to fatigue damage caused by vortex induced vibrations (VIV). Indeed, even moderate currents can induce vortex shedding, alternately at the top and the bottom of the pipeline, at a rate determined by the flow velocity. Each time a vortex sheds, a force is generated in both the in-line and cross-flow direction, causing an oscillatory multi-mode vibration. This vortex induced vibration can give rise to fatigue damage of submarine pipeline spans, especially in the vicinity of the girth welds. Traditional design for VIV is recommended in DNV-RP-F105, which limits the allowable free span length and implies whether (and when) seabed interventions are required.

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SAGE Profile, the market leader software suite for offshore pipeline analysis, is used worldwide for on-bottom roughness analyses, free span evaluation and on-bottom stress analyses. The latest versions of the software are increasingly being used to tackle more complex pipeline problems, like upheaval buckling, pipeline walking and lateral buckling. Recently, the pipeline engineering students at Cranfield University have demonstrated the ability of SAGE Profile to predict susceptibility to lateral buckling

During their research assignment for the M.Sc. in Ocean and Offshore Technology, the pipeline engineering students at Cranfield University performed SAGE Profile simulations of lateral buckling on a full 3D Digital Terrain Model. The SAGE Profile results compared well with analytical approximations (Hobbs theory) and the Abaqus benchmark.

Different methods to fire an engineered buckle were explored, like introducing (dual) sleepers, adding buoyancy modules, locally reducing seabed friction factors, or performing snake lay simulations. The results indicated that SAGE Profile can be used to evaluate the susceptibility to lateral buckling for high pressure, high temperature pipelines and flowlines.

Lateral buckle triggered at sleeper location in SAGE Profile 3D Viewer

Cranfield students with Filip Van den Abeele

The SAGE Profile team will be present at the 37th edition of the Offshore Pipeline Technology Conference (OPT) (26th and 27th February 2014, Amsterdam) and preceding Focus Day on Offshore Pipeline Buckling (25th February).

On February 25th, Jean-Christophe Ballard, a senior consultant of Fugro’s Geotechnical Consultancy Services, will make a presentation focussing on the ultimate uplift capacity of offshore pipelines in undrained clay.

During the conference, we will also present, together with Shell UK Ltd., a paper discussing soil structure interaction analyses performed to aid in the design of a rock berm to provide restraint to a surface laid pipeline in the case of full bore rupture of the line.

Join us at the Fugro booth for a Live Demo of SAGE Profile, and to meet our geotechnical engineers and pipeline consultants. We look forward to meeting you at OPT in Amsterdam!