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Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

A Recent Industry Understanding of Upheaval Buckling Design
for a Large-size Subsea Pipeline Buried through a Jet Trenching Method
Zhenguo Tu, Qiang Wang, Stian Laland Rasmussen, Per Richard Nystrøm and Samson K. Katuramu
IKM Ocean Design AS
Sandnes, Rogaland, Norway

operating at high pressure/high temperature (HP/HT) condition is toavoid upheaval buckling (UHB), which may potentially cause severe
failure / leakage of a pipeline system and associated significant
economical loss. The UHB phenomenon of a pipeline buried in a trench
is illustrated in Fig.1.

ABSTRACTThis paper presents the main findings resulting from the upheaval
buckling design challenges associated with a real industry application ofa 32” subsea pipeline, buried in a trench produced by a jet trenching
operation. The uplift mobilization distance is regarded as a criticalparameter influencing the upheaval buckling behaviour of a pipeline.
This parameter is highly uncertain, and its adequate consideration isessential to ensure a reliable UHB design. It is typically understood to bea conservative approach of applying the upper estimate value in theanalysis. However, for the project application presented in this paper aconservative backfill cover failure load (based on effective axialcompression) has been predicted when the lower estimate of the uplift
mobilization distance is applied. The uplift limit criterion appears togovern largely over the critical buckling load criterion. It may therefore
be of importance for similar future pipeline projects to give due
consideration of this aspect. The fundamental principle of thisphenomenon is explained in this paper and the opportunity of apotentially cost optimization regarding rock dumping requirement is
discussed with focus on the choice of the uplift mobilization distance,
relaxation of the design criterion, load factors as well as the uplift
ratcheting limit.

1ELEMENT SOLUTIONFEB 13 2022
09:53:58

STEP=35
SUB =15
TIME=35
SEQV(NOAVG)DMX =2.101
SMN =.322E+09
SMX =.494E+09

MXMN

Fig. 1. Illustration of upheaval buckling of a pipeline buried in a trenchand backfill covered (partly from Thusyanthan et al., 2011)
UHB is to be mitigated by an appropriate design of overburden by use of
backfill soil material for a trenched pipeline. A robust overburden design
relies on reliably accounting for governing design/construction+++++++ 3D - ELASTO-PLASTIC ANALYSIS of a curve laid pipeline-MASTER MODEL ++++
parameters consisting of out of straightness (OOS), effective axial force,
backfill soil resistances - including the uplift mobilization distance.
Upheaval buckling of a pipeline is a classical problem and there has been
extensive research conducted. The publications presented outcome fromstudies focusing on various perspectives in relation to the pipeline
upheaval buckling behaviour, including pipe soil interaction (Dickin,1994), experimental studies (Thusyanthan et al., 2010), semi-analyticalapproaches (Nielsen et al., 1990; Pedersen and Jensen, 1988; Palmer,1990), reliability analysis (Babu and Srivastava, 2010) and FE
simulations (Thusyanthan et al., 2010).
.322E+09

KEY WORDS: Large buried pipeline; jet trenching; backfill cover;upheaval buckling; uplift resistance and mobilization distance; uplift
failure criterion; upward ratcheting.

INTRODUCTION
Offshore submarine oil and gas pipelines will occasionally be trenchedand buried in order to fulfill a set of different design criteria related toflow assurance, on-bottom stability and protection against third party
loads, for example trawl gear interaction and anchor drag. While it is acommon industry practice to consider burying relatively small diameter
pipelines (except deep water applications), typically a size up to around16”, there are exceptions where pipelines of a significant size are decided
to be buried as well. One critical design aspect for these buried pipelines.341E+09.360E+09.380E+09.399E+09.418E+09.437E+09.456E+09.475E+09.494E+09

A most recognized design guideline for the UHB design in the oil andgas industry is the DNV-RP-F110 (2007). The uplift mobilisation
distance associated with the uplift resistance of the backfill soil cover is
one of the most critical parameters in determining a realistic engineering
prediction of the critical effective axial force load regarding UHB / uplift
ratcheting. It is important to realize that this parameter is highly uncertain
and shall be characterized as a statistic variable, requiring an adequate
assessment of the variation range. It appears to be a common

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