-
State of the art subsea foundation design- supporting industry
needs
Professor Susan GourvenecCentre for Offshore Foundation Systems,
University of Western AustraliaARC Centre for Geotechnical Science
and EngineeringEnergy and Minerals Institute
SUT Technical Meeting, 26 February 2014
-
Subsea development
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
Julimarfield,Apache.www.apachecorp.com
-
Subsea structure
Pazfloor,Angola.ImagecourtesyofSubsea7
B=5m,L=10md=1mV~500
600kNIdeallysmallandlightenoughtobeinstalledbypipelayingvessel
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
-
Subsea foundation - VH2M2T
Subseamudmatssubjectedtoloadingin6dof
Selfweight,biaxialhorizontalloads(fromthermalexpansionofpipelines)
Verticalandhorizontaleccentricityofloads=biaxialmomentsandtorsion
Jumper
Pipeline Mudmat
Hx
Hy V
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
-
The geotechnical design issue Classicalbearingcapacitytheory
qult =( +2)suxlotsofreductionfactors,e.g.sc,dc,ic,B,L,F,
VHM,notorsion,andHMpoorlypredicted
Output=singleallowableverticalloadorbearingpressure
Noindicationofeffectofdifferentloadcomponentsonproximitytofailure.
Conventionaldesignmethod Toolargeforpipelaying
vesseltoinstall. Requiresecondvesselon
site=$$$
Optimizeddesignmethod Smallenoughfor
pipelayingvesseltoinstall.
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
-
1. Alternative design method
Fengetal.,2014,Gotechnique
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
Failureenvelopedesignmethod
Explicitlyaccountforeffectofappliedloads,V,Hx,Hy,Mx,My,T
Explicitlyaccountforeffectofgeometry,B/L,d/B
Explicitlyaccountforshearstrengthprofile,kB/su0
,surfacecrust
Determinehowindividualvariablesaffectthedesignoutcome.
Indicatedisplacementsatfailure.
-
Caveats
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
Be wary of oversimplification.
Choice of appropriate su is central to calculation affected by
various conditions, inc. cyclic loading.
Assumptions of undrained load response.
But Neat tool for preliminary sizing.
Indicates influence of design input independent variables.
Augment with more detailed analysis for detailed design.
Tool demonstrates how improved site investigation data can have
significant impact on design.
-
Industry impact
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
-
2. Hybrid subsea foundation Mudmatwithcornerpinpiles
Increasein6dofloadcapacityovermatalone,inparticularlateralandtorsionalresistance.
Smallerfootprintsizes.
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
Gaudinetal.,2011,SUTLondonDimmocketal.,2013,ASCEJGGE
-
2. Hybrid subsea foundation Mudmat withcornerpinpiles
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
Gaudinetal.,2011,SUTLondonDimmocketal.,2013,ASCEJGGE
-
3. Internal skirt spacing Optimalspacingofinternalshearkeys
Preventshearingwithintheconfinedsoilplug.
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
-
00.20.40.60.8
11.21.41.61.8
2
-1.5 -1.2 -0.9 -0.6 -0.3 0 0.3 0.6 0.9 1.2 1.5
M
o
m
e
n
t
,
M
y
(
x
)
/
A
B
s
u
0
Horizontal load, Hx(y)/Asu0
B0L0, B1L1, B2L2, B4L4, B5L5, Solid
Failureenvelopes&failuremechanisms
Internal skirt spacing
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
Increasing # skirts
2M/HB
0
3
6, & solid
-
Designcharts
Internal skirt spacing
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
0
1
2
3
4
5
6
7
0 0.05 0.1 0.15 0.2
C
r
i
t
i
c
a
l
n
u
m
b
e
r
o
f
i
n
t
e
r
n
a
l
s
k
i
r
t
s
Equivalent embedment ratio
0 88 1010 2020 100 > 100
Feng&Gourvenec,OMAE,2013Manaetal.,ASCEJGGGE,2012
VH2M2TV/Vu 0.5 =kB/su0orkL/su0
d/B or d/L
-
4. Consolidated shear strength
Increaseininsitushearstrengthunderfoundationandstructureself
weightpriortoinserviceloading.
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
1
1.2
1.4
1.6
1.8
2
2.2
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7Preload: Vp/Vu
G
a
i
n
:
V
u
,
c
o
n
s
/
V
u
H
V
M
F
u
l
l
y
c
o
n
s
o
l
i
d
a
t
e
d
g
a
i
n
Preload, vp/vu
-
Consolidated shear strength
Gaincanbescaledlinearlyasafunctionofthedegreeofconsolidation
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
Gourvenecetal,Gotechnique,2014
P
r
o
p
o
r
t
i
o
n
o
f
f
u
l
l
y
c
o
n
s
o
l
i
d
a
t
e
d
g
a
i
n
Degree of consolidation, U = w/wf
-
5. Mobile foundations
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
Federalfundingfora3yearprojecttodevelopageotechnicaldesignframeworkformobilefoundations.
-
Toolbox for optimized design
1. 6dof
failureenvelopedesignmethodologyandcalculationspreadsheet
2. Pinpiles hybridsubseafoundation
3. Skirtspacing
4. Consolidatedshearstrength
5. Mobilefoundations
S
u
s
a
n
.
G
o
u
r
v
e
n
e
c
@
u
w
a
.
e
d
u
.
a
u
w
w
w
.
c
o
f
s
.
u
w
a
.
e
d
u
.
a
u
-
Acknowledgements:
ColleaguesatCOFS,inparticularMarkRandolph,ChristopheGaudin,XiaoweiFeng,DivyaMana,CristinaVulpeandMichaelCocjin
AustralianResearchCouncil
Ourindustrypartners,inparticularSubsea7 EMIforsponsoringthisevening
SUTfortheinvitationtotalk
Thank you for your attention!
Pleasefeelfreetocontactme:[email protected]
www.cofs.uwa.edu.au,www.emi.uwa.edu.au
