Transient behaviour of a suction caisson in sand: axisymmetric - - PowerPoint PPT Presentation

▶
transient behaviour of a suction caisson in sand
SMART_READER_LITE
LIVE PREVIEW

Transient behaviour of a suction caisson in sand: axisymmetric - - PowerPoint PPT Presentation

Oct 05, 2023 127 likes •453 views

Transient behaviour of a suction caisson in sand: axisymmetric numerical modelling B. Cerfontaine, F. Collin and R. Charlier University of Liege, Belgium 26th of May, 2016 B. Cerfontaine, F. Collin and R. Charlier RUGC2016 26/05/16 0 / 24

slide-1
SLIDE 1

Transient behaviour of a suction caisson in sand: axisymmetric numerical modelling

  • B. Cerfontaine, F. Collin and R. Charlier

University of Liege, Belgium

26th of May, 2016

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 0 / 24

slide-2
SLIDE 2

Outline

1

Context

2

Description of the case study

3

Results

4

Conclusions and perspectives

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 1 / 24

slide-3
SLIDE 3

Context

Table of contents

1

Context

2

Description of the case study

3

Results Reaction modes Monotonic simulations Cyclic simulations

4

Conclusions and perspectives

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 2 / 24

slide-4
SLIDE 4

Context

Motivations

1 EU 2020 objectives (greenhouse gas, renewable energy, energy

efficiency)

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 3 / 24

slide-5
SLIDE 5

Context

Motivations

1 EU 2020 objectives (greenhouse gas, renewable energy, energy

efficiency)

2 Basic working of soil-caisson system upon both monotonic and cyclic

loading (serviceability)

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 3 / 24

slide-6
SLIDE 6

Context

Motivations

1 EU 2020 objectives (greenhouse gas, renewable energy, energy

efficiency)

2 Basic working of soil-caisson system upon both monotonic and cyclic

loading (serviceability)

3 Identifications of components of reaction : first step to the

elaboration of a macro-element

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 3 / 24

slide-7
SLIDE 7

Context

Suction caissons for offshore foundations

Houlsby et al. (2005)

Pumping Water flows Decreasing inside pressure

Offshore wind turbines specificities light structure high overturning moment Suction caissons specificities hollow steel cylinder open towards the bottom extensively used as anchors in the North Sea monopod or tetra/tri-pod superstructure cheaply and quickly installed, reusable, Senders (2008) limited extension resistance by suction

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 4 / 24

slide-8
SLIDE 8

Description of the case study

Table of contents

1

Context

2

Description of the case study

3

Results Reaction modes Monotonic simulations Cyclic simulations

4

Conclusions and perspectives

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 5 / 24

slide-9
SLIDE 9

Description of the case study

Geometry

Seabed Sea level

Waves + Wind

Published in Cerfontaine et al. (2016), G´ eotechnique Modelling (axisymmetric)

Lid Elastic superficial layer Inner interface (top) Outer interface (skirt) Inner interface (skirt) Skirt Elastic toe Height (H) Radius (D/2)

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 6 / 24

slide-10
SLIDE 10

Description of the case study

Geometry

Seabed Sea level

Waves + Wind

Published in Cerfontaine et al. (2016), G´ eotechnique Modelling (axisymmetric)

Initial stress (interface) Height (H) Radius (D/2) Loading Initial stress (soil)

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 6 / 24

slide-11
SLIDE 11

Description of the case study

Geometry

Seabed Sea level

Waves + Wind

Published in Cerfontaine et al. (2016), G´ eotechnique Size D=7.8m and H=4m Soil-steel friction coefficient µ = 0.5 Permeability k= 5 · 10−12m2 Coefficient of lateral earth pressure at rest K0 = 1.0 Porosity n= 0.36

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 6 / 24

slide-12
SLIDE 12

Description of the case study

Prevost model for cohesionless soils - Kinematic hardening

After Elgamal (2003)

Implementation in LAGAMINE code published in Cerfontaine et al. (2014) NUMGE2014 Proceedings

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 7 / 24

slide-13
SLIDE 13

Description of the case study

Prevost model for cohesionless soils - Volumetric behaviour

p'

q

Contractive Dilative

PT line Current stress state Trace of current yield surface

η

Non-associated plastic volumetric behaviour ˙ ǫp

v = 1

3 · η2 − ¯ η2 η2 + ¯ η2 · ˙ λ η = q/p′ ˙ λ continuous plastic multiplier ¯ η phase transformation ratio, Ishihara (1975) Very simple (only 1 param.) ⇒ satisfactory to a 1st approx.

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 8 / 24

slide-14
SLIDE 14

Description of the case study

Cyclic triaxial tests (Lund Sand, Dr= 90%, Ibsen & Jakobsen (1996)) Two distinct behaviours from two initial deviatoric stress invariants

10 20 30 40 50 60 70 80 −20 −10 10 20 30 40 50 60 70

p’ [kPa] q [kPa] PT Line

10 20 30 40 50 60 70 80 −20 −10 10 20 30 40 50 60 70

p’ [kPa] q [kPa] PT Line

Full calibration process published in Cerfontaine (2014), PhD thesis

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 9 / 24

slide-15
SLIDE 15

Description of the case study

Hydro-mechanically coupled interface element Mechanical behaviour

|tT| p'

f>0 f<0 f=0 Elastic domain Plastic surface No contact µ

N

+ Penalty method Flow behaviour

Side 2 Side 1 Inside

gN fwt2 fwt1 fwl

Couplings Effective stress Storage Permeability Published in Cerfontaine et al. (2015) Computers and Geotechnics

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 10 / 24

slide-16
SLIDE 16

Results Reaction modes

Table of contents

1

Context

2

Description of the case study

3

Results Reaction modes Monotonic simulations Cyclic simulations

4

Conclusions and perspectives

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 11 / 24

slide-17
SLIDE 17

Results Reaction modes

Reaction of the caisson to applied vertical load

ΔFtot ΔFin ΔFout ΔFtop ΔFtip ΔFpw ΔFtot

Resistance to compressive load ∆Ftot ∆Fin, inner friction ; ∆Fout, outer friction ; ∆Fpw, pore water pressure (> 0) ; ∆Ftop, top effective stress ; ∆Ftip, tip effective stress.

ΔFtot ΔFtot ΔFin ΔFout ΔFpw

Resistance to extension load ∆Ftot ∆Fin, inner friction ; ∆Fout, outer friction ; ∆Fpw, pore water pressure (< 0).

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 12 / 24

slide-18
SLIDE 18

Results Monotonic simulations

Table of contents

1

Context

2

Description of the case study

3

Results Reaction modes Monotonic simulations Cyclic simulations

4

Conclusions and perspectives

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 13 / 24

slide-19
SLIDE 19

Results Monotonic simulations

Monotonic extension simulations (load controlled) Drained

−3 −2.5 −2 −1.5 −1 −0.5 −3 −2.5 −2 −1.5 −1 −0.5

∆y [mm] ∆F [MN]

∆Ftot ∆Fin ∆Fout ∆Flid ∆Ftip Upwards

Partially drained (8kPa/s)

−3 −2.5 −2 −1.5 −1 −0.5 −3 −2.5 −2 −1.5 −1 −0.5

∆y [mm] ∆F [MN]

∆Ftot ∆Fin ∆Fout ∆Flid ∆Ftip ∆Fpw Upwards

∆Fin and ∆Fout bounded ∆Fin < ∆Fout (unloading) ∆Fin and ∆Fout bounded ∆Fin < ∆Fout (unloading) ∆Fpw increasing

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 14 / 24

slide-20
SLIDE 20

Results Monotonic simulations

Pore water pressure generation during extension

  • 2.80
  • 5.70
  • 8.60
  • 11.5
  • 14.4
  • 17.3
  • 20.2
  • 23.1
  • 26.0
  • 28.9
  • 31.8
  • 34.7

Δpw [kPa] Pload = 55.5kPa

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 15 / 24

slide-21
SLIDE 21

Results Cyclic simulations

Table of contents

1

Context

2

Description of the case study

3

Results Reaction modes Monotonic simulations Cyclic simulations

4

Conclusions and perspectives

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 16 / 24

slide-22
SLIDE 22

Results Cyclic simulations

Pseudo-random and equivalent loadings

0.8 0.85 0.9 0.95 1 −10 10 20 30 40 50 60 70

Time[h] P

load [kPa]

Extreme event

0.5 1 1.5 2 −0.8 −0.6 −0.4 −0.2 0.2 0.4 0.6 0.8 1

Time [h] Fy/max(|Fy|) [−]

Extreme event Short Signal

ΔPload=45kPa Pload,av=20kPa

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 17 / 24

slide-23
SLIDE 23

Results Cyclic simulations

Pseudo-random and equivalent loadings

0.8 0.85 0.9 0.95 1 −10 10 20 30 40 50 60 70

Time[h] P

load [kPa]

Extreme event

0.5 1 1.5 2 −0.8 −0.6 −0.4 −0.2 0.2 0.4 0.6 0.8 1

Time [h] Fy/max(|Fy|) [−]

Extreme event Short Signal

ΔPload=45kPa Pload,av=20kPa

Time Time Pload,mean Pseudo-Random Equivalent

ΔT1

ΔP1 ΔP2 ΔP3 ΔP1 ΔP2 ΔP3

ΔT1

Pload Pload,mean Pload

Half-cycle analysis

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 17 / 24

slide-24
SLIDE 24

Results Cyclic simulations

Pseudo-random and equivalent loadings

0.8 0.85 0.9 0.95 1 −10 10 20 30 40 50 60 70

Time[h] P

load [kPa]

Extreme event

0.5 1 1.5 2 −0.8 −0.6 −0.4 −0.2 0.2 0.4 0.6 0.8 1

Time [h] Fy/max(|Fy|) [−]

Extreme event Short Signal

ΔPload=45kPa Pload,av=20kPa Batch 1 Batch 2 Batch 3 Batch 4

  • Nb. cycles [-]

50 28 4 1 T [s] 4.6 11 11.6 11.1 ∆P [kPa] 4.5 13.5 22.5 40.5

Time Time Pload,mean Pseudo-Random Equivalent

ΔT1

ΔP1 ΔP2 ΔP3 ΔP1 ΔP2 ΔP3

ΔT1

Pload Pload,mean Pload

Half-cycle analysis

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 17 / 24

slide-25
SLIDE 25

Results Cyclic simulations

Pseudo-random and equivalent loadings

100 200 300 400 500 600

  • 20

20 40 60 80

Pload [kPa] Pload [kPa] Pseudo-random Equivalent 1 Equivalent 2 Equivalent 3 Time [s] Time [s] Time [s] Time [s] Pload [kPa] Pload [kPa]

100 200 300 400 500 600

  • 20

20 40 60 80 100 200 300 400 500 600

  • 20

20 40 60 80 100 200 300 400 500 600

  • 20

20 40 60 80

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 18 / 24

slide-26
SLIDE 26

Results Cyclic simulations

Cyclic partially drained behaviour

100 200 300 400 500 600 −40 −20 20 40

Time [s] ∆p [kPa]

∆ pw ∆ ptot 100 200 300 400 500 600 −40 −20 20 40

Time [s] ∆p [kPa]

Envelope curves Tendency Envelope curves Tendency Envelope curves ∆ pw,p2p Envelope curves

Envelope and tendency curves : permanent and transient Loading mainly sustained by pore water pressure (PWP) Accumulation of PWP (max 5kPa) Highest accumulation during extreme event

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 19 / 24

slide-27
SLIDE 27

Results Cyclic simulations

Cyclic partially drained behaviour : displacement and PWP accumulation

200 400 600 800 1000 −1 1 2 3 4 5 6 7 8

Time [s] ∆pw [kPa]

Equiv.1 Equiv.2 Equiv.3 Random Consolidation

200 400 600 800 1000 0.5 1 1.5 2 2.5 3 3.5

∆y [mm] Time [s]

Equiv.1 Equiv.2 Equiv.3 Random Consolidation Maxima

Max PWP (extreme event sooner) Lowest PWP (random) Almost no effect of small cycles Linear and non-linear parts High accumulation for extreme event All displacements converge

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 20 / 24

slide-28
SLIDE 28

Results Cyclic simulations

Cyclic partially drained behaviour : influence of permeability

500 1000 1500 2000 0.5 1 1.5 2 2.5 3 3.5

Time [s] ∆y [mm]

5*10−13 5*10−12 5*10−11 5*10−10 k [m2] Consolidation End

−5 5 10 5 10 15 20 25

q [kPa] p’ [kPa]

5*10−13 5*10−12 5*10−11 5*10−10 k [m2] A B−12 B−11 B−10 B−13 Failure PT line

No linear trend with permeability evolution Local failure for the highest permeability (high effective stress variations) Different stress paths under the lid centre with permeability Decrease of p′ due to PWP increase or contractancy

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 21 / 24

slide-29
SLIDE 29

Conclusions and perspectives

Table of contents

1

Context

2

Description of the case study

3

Results

4

Conclusions and perspectives

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 22 / 24

slide-30
SLIDE 30

Conclusions and perspectives

Coupled modelling of a suction caisson upon monotonic and cyclic loading Importance of the partially drained behaviour (both monotonic and cyclic) Identification of different modes of resistance not activated all at the same time Complex behaviour and accumulation of settlement during a short-time storm event

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 23 / 24

slide-31
SLIDE 31

Conclusions and perspectives

Coupled modelling of a suction caisson upon monotonic and cyclic loading Importance of the partially drained behaviour (both monotonic and cyclic) Identification of different modes of resistance not activated all at the same time Complex behaviour and accumulation of settlement during a short-time storm event Perspectives

Calibration procedure and validation of the model Elaboration of a macro-element 3D simulations including lateral loading

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 23 / 24

slide-32
SLIDE 32

Conclusions and perspectives

References

Houlsby, G. T., Ibsen, L. B. & Byrne, B. W. (2005). Suction Caissons for Wind Turbines. International Symposium on Frontiers in Offshore Geotechnics, 75(September), 94. Senders, M. (2008). Suction caissons in sand as tripod foundations for offshore wind turbines. PhD Thesis, University of western Australia. Elgamal, A., Yang, Z., Parra, E. & Ragheb, A. (2003). Modeling of cyclic mobility in saturated cohesionless soils. International Journal of Plasticity, 19(6), 883-905. Ishihara, K., Tatsuoka, F. & Yasuda, S. (1975). Undrained Deformation and liquefaction of sands under cyclic stresses. Soils and Foundations, 15(1), 29 ?44. Cerfontaine, B., Collin, F. & Charlier, R. (2016). Numerical modelling of transient cyclic vertical loading of suction caissons in sand. G´ eotechnique, 66(2), 1-16. Cerfontaine B. & Charlier, R. (2014) Implicit implementation of the Prevost model. Proceedings

  • f the eight European Conference in Numerical Methods in Geotechnical Engineering.

Ibsen, L.B. & Jacobsen, F.R. (1996) Lund sand no.0. Technical report, Aalborg University. Cerfontaine (2014) The cyclic behaivour of sand, from the Prevost model to offshore

  • geotechnics. PhD Thesis, University of Li`

ege. Cerfontaine, B., Dieudonn´ e, A. C., Radu, J. P., Collin, F., & Charlier, R. (2015). 3D zero-thickness coupled interface finite element : Formulation and application. Computers and Geotechnics, 69, 124-140.

  • B. Cerfontaine, F. Collin and R. Charlier

RUGC2016 26/05/16 24 / 24