Developing a more accurate description of soil-pipe ...€¦ · 11/06/2015 1 Developing a more accurate description of soil-pipe interaction for the design of high temperature pipelines

11/06/2015

1

Developing a more accurate description of soil-pipe interaction for the design of high temperature pipelinesDavid WhiteShell EMI Professor of Offshore Engineering

Fraser BransbySenior Principal Engineer, Fugro AG

SUT Evening Technical Meeting, Perth10 June 2015

Background references• White D.J., Westgate Z., Ballard J-C, de Brier C. & Bransby M.F. 2015. Best practice geotechnical

characterization and pipe-soil interaction analysis for HPHT flowline design. Proc. Offshore Technology Conference. Houston. OTC26026-MS

• Bransby, M.F., Borges Rodriguez, A., Zhou, H., Low, H.E. & White, D.J. 2014. Sediment mobility effects on seabed resistance for unburied pipelines. Proc. Offshore Technology Conference. Paper OTC25287

• Westgate Z.J. & White D.J. 2015. Quantifying spatial variability in pipeline embedment for subsea pipeline design. Proc. Int. Conf. Offshore Mech. and Arctic Engng. OMAE2015-42292

• White D.J., Leckie, S.H.F., Draper, S., Zakarian, E. 2015. Temporal changes in pipeline-seabed condition and their effect on operating behaviour. Proc. Int. Conf. Offshore Mech. and Arctic Engng. OMAE2015-42216

• Leckie, S., Draper, S., White, D.J., Cheng, L. & Fogliani N. 2015. Lifelong embedment and spanning of a pipeline on a mobile seabed. Coastal Engineering. 95:130-146.

• Hill A. & White D.J. 2015. Pipe-soil interaction: Recent and future improvements in practice. Proc. Int. Symp. on Frontiers in Offshore Geotechnics (ISFOG).

David White (UWA), Fraser Bransby (FugroAG)SUT Evening Technical Meeting, 10 June 2015

Unravelling PSI design ranges

Pip

elin

e em

bedm

ent

Pip

e-so

il fri

ctio

n

Low estimate

High estimate


Unravelling PSI design ranges• Consolidation hardening

Pip

elin

e em

bedm

ent

Pip

e-so

il fri

ctio

n

Low estimate

High estimate

Time


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• Self-burial

Pip

elin

e em

bedm

ent

Pip

e-so

il fri

ctio

nLow estimate

High estimate

Time



• Self-burial

• Spatial variability

Pip

elin

e em

bedm

ent

Pip

e-so

il fri

ctio

n

Low estimate

High estimate

Space



• Self-burial


Pip

elin

e em

bedm

ent

Pip

e-so

il fri

ctio

n

Low estimate

High estimate



Pip

elin

e em

bedm

ent

Pip

e-so

il fri

ctio

n

Low estimate

High estimate

Time


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Axial PSI: General Model

Cycle number

Axi

al fr

ictio

n, F

A/W

(su-int/no)nc

tan res

Undrained

Drained

c/p

Effective stress, Vo

ids

ratio

, e Undrained

Dra

ined

From pipe weight

Consolidation Hardening

Cycle number, n

Mob

ilise

d st

reng

th

(su,1)

(su,n)

Effective stress,

Void

s ra

tio, e

ln R

sunsu1

R

(Partial) Consolidation Hardening

Cycle number, n

Mob

ilise

d st

reng

th

(su,1)

(su,n)

Effective stress,

Void

s ra

tio, e

Consolidation Hardening: ISB

-4-3-2-101234

-6 -4 -2 0 2 4 6

Shea

r stre

ss (k

Pa)

Horizontal displacement (mm)

Cycles 1-2 Cycles 5-6 Cycles 9-10

Boukpeti & White (2015)


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Consolidation Hardening: FEA

Yan et al (2014) David White (UWA), Fraser Bransby (FugroAG)SUT Evening Technical Meeting, 10 June 2015

Consolidation Hardening: Experiment

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 50 100 150

Axial fric

tion, F A/W

'

Axial displacement, x (mm)

12345678910111213

120 mm dia.1.4 m lengthSoft kaolin clayInitially 0.3D embedded

Smith & White 2014 David White (UWA), Fraser Bransby (FugroAG)SUT Evening Technical Meeting, 10 June 2015

Example: Downslope ‘Walking’

Typical ‘short’ flowlineon 3 seabed slope.SAGE-Profile 3D software.

Pipeline, Bathymetry and Operating Parameters ValuePipeline diameter (m) 0.3

Pipeline length (m) 4000Wall thickness (mm) 25

Submerged operating weight, W'op (kN/m) 1.5Seabed slope, (°) 3

Temperature range (startup to shutdown), T (°) 80

Soil and PSI Parameters Value

Undrained axial friction factor, FA/W'op = ud 0.4Drained axial friction factor, FA/W'op = d 0.8

Mobilization distance, xmob (mm) 10Volumetric stiffness ratio, / 0.1

Coefficient of consolidation, cv (m2/yr) 0.2White et al. (2015)

Limiting Axial Friction Cases

0

0.5

1

1.5

0 5 10 15 20 25

Acc

umul

ated

pip

elin

e w

alk

[m]

Cycles of startup or shutdown

No walking (FA/W = 0.8)

Solid line: analytical solution (Carr et al. 2006)Dotted line: analytical solution with elastic correction

Hollow dots: SAGE Profile FE simulations

White et al. (2015) David White (UWA), Fraser Bransby (FugroAG)SUT Evening Technical Meeting, 10 June 2015

11/06/2015

5

0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25

Axi

al E

quiv

alen

t Fri

ctio

n Fa

ctor

, A


With Consolidation Hardening

Drained

(Initial) Undrained


0

0.5

1

1.5

0 5 10 15 20 25

Acc

umul

ated

pip

elin

e w

alk

[m]


With Consolidation Hardening

No walking

Solid line: analytical solution (Carr et al. 2006)Dotted line: analytical solution with elastic correction

Hollow dots: SAGE Profile FE simulations

Acceptable walking


0

0.2

0.4

0.6

0.8

1

0 5 10 15 20 25

Axi

al E

quiv

alen

t Fri

ctio

n Fa

ctor

, A


Friction With Operational Effects

Drained

(Initial) Undrained

Partial consolidation cases


0

0.5

1

1.5

0 5 10 15 20 25

Acc

umul

ated

pip

elin

e w

alk

[m]


Range of Walking Responses

No walking

Acceptable walking

Acceptable walking?

Acceptable walking?


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Consolidation Hardening: Field?

(m)

Hill & White (2015)David White (UWA), Fraser Bransby (FugroAG)SUT Evening Technical Meeting, 10 June 2015


• Self-burial

Pip

elin

e em

bedm

ent

Pip

e-so

il fri

ctio

n

Low estimate

High estimate

Time


As-laid condition

Leckie et al. (2015)David White (UWA), Fraser Bransby (FugroAG)SUT Evening Technical Meeting, 10 June 2015

Intermittent self-burial and spanning

Leckie et al. (2015)David White (UWA), Fraser Bransby (FugroAG)SUT Evening Technical Meeting, 10 June 2015

11/06/2015

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0.0002 m/s2

1 m/s after 5000 s. Impact on temperature profile

50°C

0.65DSimon Leckie, Erich ZakarianOMAE 2015-42216



• Self-burial


Pip

elin

e em

bedm

ent

Pip

e-so

il fri

ctio

n

Low estimate

High estimate

Space


0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

4500 4600 4700 4800 4900 5000Pi

pe e

mbe

dmen

t, w

/DKP (m)

Pipeline embedment variability

Westgate & White (2015) David White (UWA), Fraser Bransby (FugroAG)SUT Evening Technical Meeting, 10 June 2015

11/06/2015

8

0

0.5

1

1.5

2

2.5

3

4500 4600 4700 4800 4900 5000

Lat

eral

bre

akou

t fri

ctio

n, H

brk/W

'

KP (m)

ActualP10P90

Breakout friction variability


500

1000

1500

2000

2500

4500 4600 4700 4800 4900 5000

Hob

bs b

uckl

ing

forc

e, P

Hob

bs(k

N)

KP (m)

ActualP10P90

Buckle initiation force variability


500

1000

1500

2000

2500

0 5000 10000 15000 20000

Hob

bs b

uckl

ing

forc

e, P

Hob

bs(k

N)

KP (m)

ActualP10P90




500

1000

1500

2000

2500

0 5000 10000 15000 20000H

obbs

buc

klin

g fo

rce,

PH

obbs

(kN

)KP (m)

ActualP10P90

Westgate & White (2015)

Envelope of possible buckle initiation force


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More tolerable design frictions

Roberts & Taavale (OTC 2014)See also: Gerginov et al. (OMAE 2014), Bruton & Carr (OPT 2015)

Less onerous UB friction

Full range

Conditional range

Bransby et al. (OTC2014)Breakout friction (initiation)

Res

idua

l fric

tion

(tole

rabi

lity)

Concluding comments

• Design pipe-soil friction ranges mask temporal and spatial effects

• Consolidation hardening – rise in axial friction• Potential reduction in pipeline walking

• Self-burial – increase in thermal insulation and stability• Potential improvement in corrosion and/or flow assurance• Potential reduction in (secondary) stabilisation measures

• Spatial variability• Less onerous buckling design via better PSI characterisation


Developing a more accurate description of soil-pipe interaction for the design of high temperature pipelinesDavid WhiteShell EMI Professor of Offshore Engineering

Fraser BransbySenior Principal Engineer, Fugro AG

SUT Evening Technical Meeting, Perth10 June 2015

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Developing a more accurate description of soil-pipe ...€¦ · 11/06/2015 1 Developing a more accurate description of soil-pipe interaction for the design of high temperature pipelines