Numerical simulations of pipe–soil interaction during large lateral movements on clay

Abstract

The soil resistance during large lateral movements of pipelines across the seabed is an important input to design solutions for the management of thermal and pressure-induced expansions. To investigate this behaviour, a large-deformation finite-element (LDFE) analysis method involving frequent remeshing was employed. The LDFE method allows the changing geometry of the seabed when disturbed by the pipeline to be incorporated. Also, the effects of strain rate and strain-softening on the undrained shear strength of the soil were accounted for. A back-analysis of a centrifuge modelling simulation was first performed, for validation, and then a parametric study varying the pipe weight and initial embedment was undertaken. The results show that a steady state is generally reached at large displacements, reflecting a balance between the growth of a soil berm ahead of the pipe and the softening of the disturbed soil. The initial breakout response matched well with previously established failure envelopes, and a new interpretation has been proposed to capture the large-displacement response. The 'effective embedment' concept is used to rationalise the influence of the soil berm ahead of the pipe. This leads to simple new relationships for predicting the steady-state residual lateral resistance, which provide more accurate predictions of the LDFE response than previously established solutions. The complete load-displacement response over large movements was also shown to be well fitted by an exponential relationship, albeit for the specific case of lateral movements under constant vertical load.La résistance du sol au cours de mouvements latéraux substantiels des canalisations sur le fond marin est un élément important pour la conception de solutions pour la gestion d'expansions thermiques et induites par la pression. Pour examiner ce comportement, on a utilisé une méthode d'analyse à fortes déformations aux éléments finis [large deformation finite element (LDFE)] comportant des remaillages fréquents. La méthode LDFE permet d'incorporer la géométrie variable du fond marin lorsqu'il est dérangé par la canalisation. En outre, on tient également compte des effets de la vitesse de déformation et du radoucissement sur la résistance du sol au cisaillement. On effectua en premier lieu une analyse régressive de la simulation de la modélisation centrifuge, pour la validation, puis une étude paramétrique, en variant le poids du tuyau et l'encastrement initial. Les résultats démontrent que l'on parvient généralement à un équilibre avec des mouvements substantiels, en reflétant ainsi l'équilibre entre l'expansion d'une berme de sol devant la canalisation et l'adoucissement du sol dérangé. La percée initiale en réponse correspondait bien aux enveloppes de rupture établies précédemment, et une nouvelle interprétation est proposée pour saisir la réaction aux mouvements substantiels. On utilise le concept d'« encastrement efficace » pour rationaliser l'influence de la berme de sol devant la canalisation. Ceci engendre de nouveaux rapports...

Large deformation finite element analyses in geotechnical engineering

“…The advantage of RITSS is that the remeshing and interpolation strategy can be coupled with any standard FE program, such as the locally developed program AFENA [7] and the commercial package Abaqus/Standard, through user-written interface codes. The potential of the approach has been highlighted by varied two-dimensional (2D) and three-dimensional (3D) applications of monotonic and cyclic penetration of penetrometers [19,52], penetration of spudcan foundations for mobile jack-up rigs [16,17,51], lateral buckling of pipelines [49,8] and uplift capacity and keying of mooring anchors [31,[43][44][45]47,38,39]. More recently, RITSS was extended from static to dynamic analyses [48].…”

Modelling large plastic deformations of cohesive soils using sequential limit analysis

“…A number of other advanced numerical approaches are available for the analysis of geotechnical problems involving large plastic deformations. These include the material point method, [31][32][33][34] smoothed particle hydrodynamics, [35][36][37][38] and the distinct element method, [39][40][41][42][43][44] although at present the most widely used approaches are FE-based methods such as the arbitrary Lagrangian-Eulerian, 45,46 remeshing and interpolation technique with small strain (RITSS), [47][48][49][50] and coupled Eulerian-Lagrangian (CEL) [51][52][53][54][55][56][57][58] techniques. The RITSS method originally developed by Hu and Randolph 47 is an improved arbitrary Lagrangian-Eulerian approach that divides a large-deformation problem into a series of small-deformation FE analyses.…”

Pipeline Lateral Buckling: Realistic Modelling of Geotechnical Variability and Uncertainty

“…The BE soil strength was adopted throughout. Single values of the 100 Horizontal out-of-straightness, HOOS Sine function: 0.3m amplitude, 100 m wavelength mobilization distances have also been used throughout, even though they can be influenced by pipe embedment (Chatterjee et al 2012). The LE (P 2.3 ), BE (P 50 ) and HE (P 97.7 ) The uniform friction FE cases use lateral resistance parameters that are calculated from the distribution derived for the 'Variable' case, and are shown in Table 4and are also marked on Figure 7.…”