Luger Modeling Soil-structure Interaction

8/18/2019 Luger Modeling Soil-structure Interaction

1/87

10 december 2015

Developments in modelling techniquesof soil-water-structure interaction

History, examples and practical applications

Dirk Luger


2/87

10 december 2015

Contents

Introduction and main messages

History and lessons learned as a journey through time

• Storm Surge Barrier “Maeslantkering” near Rotterdam (1995)

• Palm Deira earthquake deformations (2006)• Incheon bridge ship collision protection (2006)

• Earthquake amplification factors (2009)

• Windjack spudcan impact study (2012)

• Marsrover wheel-soil interaction (2013)

• Burgum bridge pier protection (2015)

Closure


3/87

10 december 2015


• My background: more emphasis on predicting soil structure

behaviour as realistic as possible rather on calculations thataim to prove that a certain design code or standard is

complied with. That comes later.

• Another reason for that comes from my involvement in

forensic geotechnical engineering. That’s an area where

understanding what actually happened is crucial.

• This requires selection of parameters fit for the job. Purpose

of the calculation and the mechanisms that develop can

determine to a large extent what the proper set of soil

parameters is.

You will seldom get the proper soil parameters “of the

shelf”. You’ll have to make them consistent with your

engineering problem.


4/87

10 december 2015


• A voyage through time to put what we can do nowadays into

perspective

• Quality and power of the tools at our disposal have increasedenormously

• With that the risk that calculation results are taken for granted

has increased as well (they look nice and “everything is

modeled, so it has to be OK…..)

You have to keep thinking, train your engineering

judgment and learn to trust it. Simple checks can

reveal a lot!


5/87

10 december 2015


• When extrapolating beyond tested ranges or application areas

verification of our models by feedback from actual behaviour (monitoring structures) and from model tests is

indispensable.

• Whenever you’re venturing in an area where you haven’t been

before, make sure you’ve done everything to verify that yourcalculations are reliable.

Calculation Physical model Real Structure

Feedback loops


6/87


7/87

Maeslantkering

Storm Surge Barrier


8/87


9/87


10/87


11/87

Foundation block

North door

Dry dock

Main truss

Barrier sill

Control building

Ball joint

rimary sheet pile wall

Driving unit

Main components, North side

Sea

Rotterdam, river

Back-up sheet pile wall


12/87


13/87

And actually, during a design meeting on site, in which some people

expressed their doubt regarding this risk we were suddenly warned

that a ship had collided with the main sheetpile wall, fortunately at a

moment and a place which did not lead to flooding of the building

pit…..


14/87

Geotechnical design calculations

• ‘Traditional’ settlement calcs.(level of terrain, settlement of foundation block)

• 2-D FEM calculations(parallel to main loading direction, perpendicular to

sheetpile wall, before and after ship collision)

• BEM calculations(Stresses under foundation block)

• Discrete element dynamic calculations

(Ship collision effects)


15/87

Asymmetric loading and combined perpendicular and in-

plane loading of the sheet pile wall, both through soil andvia anchors.

Having to account for

interaction between:

- Foundation block- Back-up sheetpile wall

- Main sheetpile wall

Interaction


16/87

Parallel modeling (direction of main load)

Displacements


17/87

Perpendicular modeling

Displacements

Loads from parallel

and perpendicularcalculations were

combined to determine

the final dimensions


18/87

3-D BEM calculations(Stresses under foundation block)

+ =

+

=

Self-weight

Surrounding

ballast

Combination of both

0.2 MPa

0 MPa

-0.1 MPa

-0.1 MPa

0.3 MPa

0.2 MPa

0.1 MPa


19/87


20/87

Construction of the dock at the South side

C t ti f th d i th d k


21/87

Construction of the door in the dock


22/87

The main truss

500 mm camber during supported construction80 mm camber after removal of supports


23/87

and closed….


24/87

Earthquake induced displacements

A method developed in the context of thePalm Deira development

10 december 2015


25/87

Seismic Risk 2008 26

Question

How to verify that my

embankment structureremains within acceptable

deformation limits if the

“design earthquake” occurs?

+0.6

+0.4

+0.2

0.0

-0.2

-0.4

-0.6


26/87


27/87


Sliding Block

Use published graphs or

perform own integration ofselected time-histories to

determine earthquake-

induced displacement.


28/87


Sliding block

PGA

Ayield

• Advantage:

Simple – easy to evaluate for many time histories• Disadvantage:

Only one displacement value (for the “sliding block”)

Not accounting for water next to the slope


29/87


Sliding block

PGA = 0.4 g

ay=0.2 g ay=0.1 gay=0.25 g

• Advantage:

Simple – easy to evaluate for many time histories• Disadvantage:

Only one displacement value (for the “sliding block”)

Not accounting for water next to the slope

Not accounting for failure in overlying layers


30/87


Dynamic FE analysis

Actual acceleration time history as

boundary condition at the base of

the mesh.

+ Continuous deformation field

- CPU intensive

- One time-history is not sufficient

- Free water causes problems


31/87


Deforming Continuum Method

Apply a constant horizontal acceleration at the base of the model

and observe what acceleration level can be transferred tothe different parts of the embankment

Each line represents 0.2 m/s2 = 0.02 g


32/87


Excess pore pressures

• Estimate on basis of ‘standard’ procedures: Cyclic shear stress level andrelative density of the soil.

• At the onset of the earthquake excess pore pressures a zero, by the end

they have reached their maximum value.

• Current approach: use the average…..

+0.6

+0.4

+0.2

0.0

-0.2

-0.4

-0.6

Entering excess pore pressures in

the model by reduction of the

material strength: at 50% excess

pore pressure we introduce a

material that has 50% of its original

strength:

Φnew = atan(0.5 tan(Φorg ))


33/87


Sample

Mesh

Hor. acceleration

Vert. acceleration

Shear strains


34/87


Accelerations and displacements

Ayield-vert [g]

Ayield-hor [g]

-0,12 ; -0,065

-0,11 ; -0,04 -0,07 ; -0,04

-0,04; -0,02

-0,035 ; -0,005

Verpl-vert [cm]

Verpl-hor [cm]

≈ 10 cm

≤ 1 cm


35/87


In short: A nice method filling “the gap”?


36/87

Incheon Bridge Ship collision prevention

10 december 2015


37/87


38/87

Idealized prototype – 20 m diameter

10 december 2015


39/87

The dolphin model

10 december 2015


40/87

Modelling the sheetpile

10 december 2015


41/87

Set-up of the model

10 december 2015

sand filled

container

water basin

assembly plate

actuator dolphin

moving mass

mounting plate


42/87

Set-up of the model

10 december 2015


43/87

After the test

10 december 2015


44/87

Forces derived from ship slowdown

10 december 2015


45/87

10 december 2015


46/87


47/87

Earthquake amplification factors

10 december 2015

E th k lifi ti f t


48/87

10 december 2015

Earthquake amplification factors

Limits to PGA

and amplification

Li it t l ti li i l i


49/87

10 december 2015

Limit to acceleration - preliminary analysis

0 1,0 2,0 3,0 4,0 5,0-6,0

-4,0

-2,0

0,0

2,0

4,0

Dynamic time [s]

Acceleration

CP stand 0.5g...

Point A -394.4

Point B -397.1

Point C -399.7

Point D -401.5

Point E -404.7

Point F -410.6

Point G -427.0

Point H -441.7

Point I -456.7

Point J -464.0

Demonstrated mechanism but needed clearer presentation

M h i


50/87

10 december 2015

Mechanism

M1

Su1

M2

Su2

M3

| Peak acceleration | < Su1 / M1

So in the top layer 2 values

| Peak acceleration | < (Su1 ± Su2) / M2

So for an intermediate layer 4 values

T t f i l i l


51/87

10 december 2015

Try out for simple signal

Input at base 1g at 1Hz

V l iti k it l


52/87

10 december 2015

Velocities make it clear

0 1,0 2,0 3,0 4,0 5,0-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

2,0

Dynamic time [s]

Vx [m/s]

Time_vx

Point A

Point J

Point I

Point H

Point G

Point F

Point E

Point D

Point C

Point B

V l iti k it l


53/87

10 december 2015

Velocities make it clear

0 1,0 2,0 3,0 4,0 5,0-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

2,0

Dynamic time [s]

Vx [m/s]

Time_vx

Point A

Point J

Point I

Point H

Point G

Point F

Point E

Point D

Point C

Point B

Amplification at 1g base acc


54/87

10 december 2015

Amplification at 1g base acc.

Input at base 1g at 0.4 Hz


55/87


56/87

10 december 2015

WindJack

Spudcan-seabed impact interaction

The WindJack JIP


57/87

06-Feb-14

The WindJack JIP

Soil-Structure Interaction Modelling 59

The WindJack JIP


58/87

06-Feb-14

The WindJack JIP


The WindJack JIP


59/87

06-Feb-14

The WindJack JIP


The WindJack JIP


60/87

06-Feb-14

The WindJack JIP


The WindJack JIP


61/87

06-Feb-14

The WindJack JIP


Forces have to be

corrected for inertia

effects.

Note the force to set

the spudcan in motion

and the force to stop it

again.

The WindJack JIP


62/87

06-Feb-14

The WindJack JIP


Initial analytical spudcan-

seabed interaction model

performance.

Still without hydro-

dynamic effects, inertia

and rate effects.

The WindJack JIP


63/87

06-Feb-14

The WindJack JIP


The WindJack JIP


64/87

06-Feb-14

The WindJack JIP

MPM calculation results



65/87

10 december 2015

Marsrover wheel-soil interaction


66/87

Previous work: Discrete Element Method (DEM)


67/87

Previous work: Discrete Element Method (DEM)

advantage: grousers possible, numerical stability

disadvantages:

• often 2D, unrealistic soil transport (impossible to go sideways)

• parameters for particles difficult to relate to physical quantities

• less suitable for compactive geomaterials (powder like)

70

Example of coupled Eulerian-Lagrangian FEM


68/87

Example of coupled Eulerian Lagrangian FEM

Eulerian soil model and rigid (Lagrangian) wheel.

71

Wheel/soil is half because of symmetry

Flexible wheel modeling


69/87

Flexible wheel modeling

Diameter 25 cm, width 11.2 cm.

grousersshell

Deformable

body

Only half of the wheel is

modeled (symmetry in FEM

model)

Rigid wheel modeling


70/87

Rigid wheel modeling

Diameter 25 cm, width 11.2 cm.

Same features as flexwheel, in rigid body

constraint

Only half of the wheel is

modeled (symmetry in FEM

model)


71/87

Rigid wheel 60% slip


72/87

10 december 2015

Burgum bridge pier protection

Analysis of bridge pier


73/87

Analysis of bridge pier

10 december 2015

Little effect of meshing ……


74/87

Little effect of meshing ……

10 december 2015

Soil parameters


75/87

So pa a ete s

Dr γsat eini E50_ref Eoed_ref Eur_ref G0_ref γ0.7 φ Ψ(*)

% [kN/m3] [-] [kPa] [kPa] [kPa] [kPa] [%] [degr] [degr]

50 17.0 0.60 35000 35000 105000 94000 0.0150 34.3 4.3(2.15)

75 18.0 0.52 50000 50000 150000 111000 0.0125 37.4 7.4

(3.7)

65 17.6 0.55 44000 44000 132000 104200 0.0135 36.1 6.1(3.05)

10 december 2015

Parameters for larger strains


76/87

g

10 december 2015

Interface strength @ sheetpiles


77/87

g @ p

10 december 2015

a part where soil-soil or concrete-

concrete friction is mobilized anda strength reduction factor of 1.0

applies and

a part where soil-steel or

concrete-steel friction is

mobilized where typically a

strength reduction factor of 0.67is applied.

Rinter = (422/1160)*0.67 + ((1160-422)/1160)*1.0 = 0.88

Effect of lower dilatancy


78/87

y

10 december 2015

Still room for optimisation: from 22m to 18m


79/87

p

10 december 2015

Effect of the bridge


80/87

g

10 december 2015


81/87


82/87

10 december 2015

Movement of the bridge


83/87

g

10 december 2015

Results


84/87

10 december 2015


85/87

10 december 2015

Closure – main messages


86/87

10 december 2015

• Train your engineering judgment and learn to trust it.

Simple checks can reveal a lot!

• Select proper soil parameters, consistent with your

engineering problem.

• Verify models by feedback from actual behaviour

(monitoring of structures) and by performing modeltests.

Closure - thanks


87/87

For further info on Deltares or this presentation feel free to contact:

In the Netherlands:Dirk Luger [email protected] M:+31 6 2049 1414

In Dubai:

Geoff Toms [email protected] M:+971 4 337 8353
mailto:[email protected]:[email protected]:[email protected]:[email protected]

Documents

Luger Modeling Soil-structure Interaction