Download - 120403102 Pipeline Soil Interaction
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Shawn Kenny, Ph.D., P.Eng.Assistant ProfessorFaculty of Engineering and Applied ScienceMemorial University of [email protected]
ENGI 8673 Subsea Pipeline Engineering
Lecture 15: Pipeline/Soil Interaction
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2 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Lecture 15 Objective
to examine engineering models to analysegeotechnical loads, pipeline/soil interaction and structural load effects for offshore pipelines
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3 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Overview
Geotechnical Loads Soil mechanical behaviour
Pipeline/Soil Interaction Load transfer mechanisms
Structural Load Effects Pipeline mechanical response
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4 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Design Considerations Installation
Pipeline embedment On-bottom roughness
Mechanical response, free spans Intervention
Pre-sweep, clearance Trenching
Natural in-fill, mechanical backfill Rock dump
Operations Thermal expansion Lateral and upheaval buckling On-bottom stability
Ref: Langley (2005)
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5 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Geotechnical Loads Soil Mechanics
Seabed Surveys Remote sensing In-situ testing and sample recovery Index and laboratory testing
Key Issues Soil type Strength
parameters Load-
displacementbehaviour
Ref: BCOG (2001)
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6 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Pipeline/Soil Interaction Engineering Tools
Guidance documents ALA, DNV, NEN
Numerical models Structural Continuum
Physical models Full-scale Large-scale Centrifuge
Key Issues Load transfer mechanisms Stress or strain based design Model uncertainty
Ref: C-CORE
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7 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Structural Load Effects
Design Checks Limit States
SLS ULS
Stress Combined loading
criteria Strain
Rupture Local buckling
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8 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Pipeline/Soil Interaction Analysis
Structural Finite Element Procedures Standard tool Rigid pipeline/structure Soil load-displacement
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9 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Soil Load-Displacement Relationships
Axial
Transverse Lateral
Vertical Upward
Vertical DownwardRef: ALA (2001)
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10 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Trench Effects
Engineering ModelsLoad-Displacement Centrifuge
models Large-scale
physicalmodels
Continuum FEA Ref: Phillips et al. (2004)
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11 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Buried Performance
Thermal Flow assurance
Mechanical Uplift, flotation, subsidence during pipe lay Upheaval buckling during operations
Ref: C-CORE
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12 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Example 15-01
Calculate the virtual anchor point, axial strain and end deflection due to thermal expansion for a buried pipeline
Design condition Partial restraint
Shore approach Platform tie-in
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EN 8673 Subsea Pipeline Engineering Lecture 15Example 15-01
Winter 2008
Example 15-01
Calculate the anchor point, axial strain and end deflection due to thermal expansion for a buried offshore pipelinelocated outside the 500m excursion limit.
DEFINED UNITS
MPa 106Pa:= kPa 103Pa:= GPa 109Pa:= C K:= kN 103N:=
PIPELINE SYSTEM PARAMETERS
Nominal Outside Diameter Do 273.1mm:=Initial Selection Nominal Wall Thickness (Sec.5 C203 Table 5-3) tnom 9.525mm:=External Corrosion Protection Coating Thickness tcpc 0mm:=Fabrication Process (Sec.7 B300 Table 7-1) [SMLS, HFW, SAW] FAB "SMLS":=Corrosion Allowance (Sec.6 D203) tcorr 3mm:=Elastic Modulus E 205GPa:=Specified Minimum Yield Stress (Sec.7 B300 Table 7-5) SMYS 450MPa:=Speciifed Minimum Tensile Stress (Sec.7 B300 Table 7-5) SMTS 535MPa:=Coefficient of Thermal Expansion T 1.15 10
5 C 1:=Poisson's Ratio 0.3:=Pipeline Route Length Lp 25km:=Linepipe Density s 7850kg m
3:=Concrete Coating Thickness tc 50mm:=Concrete Coating Density c 3050kg m
3:=OPERATATIONAL PARAMETERS
API Gravity API 38:=Product Contents Density
cont 1000 kg m 3 141.5131.5 API+:= cont 835 m3 kg=
Design Pressure (Gauge) Pd 10MPa:=Safety Class (Sec.2 C200-C400) [L, M, H] SC "M":=Design Pressure Reference Level href 5m:=Temperature Differential T 50 C:=Maximum Water Depth hl 0m:=Seawater Density w 1025kg m
3:=Hydrotest Fluid Density t 1025kg m
3:=
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EN 8673 Subsea Pipeline Engineering Lecture 15Example 15-01
Winter 2008
GEOTECHNICAL PARAMETERS
Undrained Shear Strength Cu 25kPa:=Adhesion Factor soil 0.25:=
DNV OS-F101 PARTIAL FACTORS AND DESIGN PARAMETERS
System Operations Incidental/Design Pressure Factor (Sec.3 B304) inc_o 1.10:=System Test Incidental/Design Pressure Factor (Sec.3 B304) inc_t 1.00:=Material Resistance Factor (Sec.5 C205 Table 5-4) m 1.15:=Safety Class Resistance Factor (Sec.5 C206 Table 5-5) SC 1.138:=Material Strength Factor (Sec.5 C306 Table 5-6) U 0.96:=Maximum Fabrication Factor (Sec.5 C307 Table 5-7)
fab 1.00 FAB "SMLS"=if0.93 FAB "HFW"=if0.85 FAB "SAW"=if
:= fab 1.00=
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EN 8673 Subsea Pipeline Engineering Lecture 15Example 15-01
Winter 2008
Diameter Fabrication Tolerance(Sec.7 G200 Table 7-17)
Do max 0.5mm 0.0075 Do, ( ) FAB "SMLS"= Do 610mmif0.01 Do FAB "SMLS"= Do 610mm>ifmin max 0.5mm 0.0075 Do, ( ) 3.2mm, ( ) FAB "HFW"= Do 610mmifmin 0.005 Do 3.2mm, ( ) FAB "HFW"= Do 610mm>ifmin max 0.5mm 0.0075 Do, ( ) 3.2mm, ( ) FAB "SAW"= Do 610mmifmin 0.005 Do 3.2mm, ( ) FAB "SAW"= Do 610mm>if
:= Do 2.048 mm=
Wall Thickness Fabrication Tolerance(Sec.7 G307 Table 7-18)
tfab 0.5mm FAB "SMLS"= tnom 4mmif0.125 tnom FAB "SMLS"= tnom 4mm>if0.125 tnom FAB "SMLS"= tnom 10mmif0.100 tnom FAB "SMLS"= tnom 25mmif3mm FAB "SMLS"= tnom 30mmif0.4mm FAB "HFW"= tnom 6mmif0.7mm FAB "HFW"= tnom 6mm>if1.0mm FAB "HFW"= tnom 15mm>if0.5mm FAB "SAW"= tnom 6mmif0.7mm FAB "SAW"= tnom 6mm>if1.0mm FAB "SAW"= tnom 10mm>if1.0mm FAB "SAW"= tnom 20mm>if
:= tfab 1.191 mm=
Material Derating (Sec.5 C300 Figure 2)
SMYS 0MPa T 50C
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EN 8673 Subsea Pipeline Engineering Lecture 15Example 15-01
Winter 2008
ENGINEERING ANALYSIS
PIPELINE GEOMETRIC PROPERTIES
Inside Pipeline Diameter (Operations Case)
Di_o Do 2. tcorr 2. tfab:= Di_o 264.72 mm=Inside Pipeline Radius (Operations Case)
Ri_o 0.5 Di_o:= Ri_o 132.36 mm=Effective Outside Pipeline Diameter
De Do 2. tcpc+ 2. tc+:= De 373.10 mm=Pipeline Steel Area
Ast
4Do
2 Do 2 tnom( )2 := Ast 7.89 103 mm2=Concrete Area
Ac
4Do 2 tc+( )2 Do2 := Ac 5.08 104 mm2=
Effective Outside Pipeline Area
Ae
4Do 2 tc+( )2:= Ae 1.09 105 mm2=
Inside Pipeline Area
Ai
4Di_o
2:= Ai 5.50 104 mm2=
BUOYANCY FORCE (per meter basis)
BF g m w Ae c Ac s Ast( ):= BF 1.03 kN=Buoyancy Force Check
BFchk "NEGATIVE BUOYANCY" BF 0
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EN 8673 Subsea Pipeline Engineering Lecture 15Example 15-01
Winter 2008
Distance to Virtual Anchor Point - Assumes constant temperature (conservative) - Equation 9 of Palmer and Ling (1981) OTC4067
z Pd Ri_o2
f1 2 2 tnom
Pd Ri_oE T T+
:= z 157.51 m=
Virtual Anchor Length Check
zchk "VIRTUAL ANCHOR OK" z 0.5 Lp= Z)
l Pd Ri_o
tnom E T T:= l 76.19 MPa=
EQUIVALENT STRESS CHECK
eq h2
h l l2+:= eq 293.73 MPa=eqchk "EQUIVALENT STRESS OK" eq 0.9 SMYS
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18 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
Reading List http://www.fugro.com/survey/offshore/gcs.asp
ALA (2001). Guideline for the Design of Buried Steel Pipe. July 2001, 83p.[2001_ALA_Design_Guideline.pdf]
Cathie, D.N., Jaeck, C., Ballard, J.-C. and Wintgens, J.-F. (2005). Pipeline geotechnics state-of-the-art. Frontiers in Offshore Geotechnics, ISFOG, ISBN 0 415 39063 X, pp.95-114[2005_Cathie_PSI.pdf]
Palmer, A.C. and Ling, M.T.S. (1981). Movements of Submarine Pipelines Close to Platforms. Proc., OTC, OTC 4067, pp.17-24.
Palmer, A.C., Ellinas, C.P., Richards, D.M. and Guijt, J. Design of Submarine Pipelines Against Upheaval Buckling. Proc., OTC, OTC 6335, pp.551-560.
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19 ENGI 8673 Subsea Pipeline Engineering Lecture 15 2008 S. Kenny, Ph.D., P.Eng.
References http://en.wikipedia.org/wiki/Geotechnical_engineering http://en.wikipedia.org/wiki/Soil_mechanics BCOG (2001). BC Offshore Oil & Gas Technology
Update, JWEL Project No. BCV50229, October 19, 2001 DNV (2007). Submarine Pipeline Systems. Offshore
Standard, DNV OS-F101, October 2007, 240p. Langley, D. (2005). A Resourceful Industry Lands the
Serpent, Journal of Petroleum Technology, 57(10), 6p. Phillips, R. A. Nobahar and J. Zhou (2004). Trench
effects on pipe-soil interaction. Proc. IPC, IPC 04-0141, 7p.
ENGI 8673 Subsea Pipeline EngineeringLecture 15 ObjectiveOverviewDesign ConsiderationsGeotechnical Loads Soil MechanicsPipeline/Soil InteractionStructural Load EffectsPipeline/Soil Interaction AnalysisSoil Load-Displacement RelationshipsTrench EffectsBuried PerformanceExample 15-01Example 15-01 (cont)Example 15-01 (cont)Example 15-01 (cont)Example 15-01 (cont)Example 15-01 (cont)Reading ListReferences