MPM-DREDGE PIAP-GA-2012-324522

Next Generation Geo Software: Large deformations and soil-water interaction

Alexander Rohe

16 June 2014 | GeoKlantendag Deltares | Delft, The Netherlands

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Proposition

The material point method (MPM) closes the gap between

soil mechanics and fluid dynamics

…a soil mechanics perspective…

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Development of a (new) advanced method

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FEM: elements become inaccurate / unstable if distorted too much

Material Point Method (MPM)

- can model large deformation

- no problems with mesh distortion

- state variables are traced by material points

- enhancement of FEM (re-using established knowledge)

Benefits of the Material Point Method

deformed mesh (at true scale)

FEM

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Basic numerical approaches

- material does not cross elements

- nodes remain on boundary

- mesh distortion?

- material flows through a fixed mesh

- no mesh distortion

- state parameters?

Lagrangian : mesh deforms as the body deforms SOIL MECHANICS

Eulerian : material flows through a fixed mesh FLUID MECHANICS

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Basic concept of MPM: decoupling material from mesh

Lagrangian Eulerian

initial configuration deformation after resetting the mesh

in each calculation step :

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Basic principle of the Material Point Method

initial position of material points

final position of material points

Eulerian background mesh & Lagrangian material points

material points move through mesh

MPM

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Example of the Material Point Method

total displacements [m]

Example: collapsing soil column

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Validation: Submerged slope failure & liquefaction Simulation of tests in dredging flume (Eastern Scheldt Barrier)

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Experimental setup: natural slope (submerged)

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Experiment: initial vs. final situation

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Results of numerical analysis with MPM

displacements [m]

vertical effective stresses [kPa]

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Final situation: experiment vs. MPM simulation

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Validation: Pile installation Simulation of centrifuge tests

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Pile installation: centrifuge tests

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Pile installation: MPM simulation

horizontal stress during installation

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Pile installation: experiment vs. simulation

installation phase

static load test

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Pile driving – frictional pile (m=0.5), RD = 30.4% (loose)

Volumetric strain Shear strain Displacement

Ux Uy s v

- -2 m

0.4 m

-0.2 m

0.2 m

-0.3

0.3

0.0

5

each step in the animation represents one blow (total 27 blows)

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Examples: Soil – water interaction and phase transition Flow, erosion and breaching

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MPM for soil – water interaction

(source: Wieckowski, 2013)

9

3

3

2.1284 10 Pa

0.8905 10 Pa s

1000 kg/m

m

l

K

water

o o

3

1 MPa

0.3

30 , 0

2850 kg/m

s

s

E

soil

9 2

1.0 mm

0.474

2.57 10 m

sd

n

SEEPAGE FLOW

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MPM for soil – water interaction

BREACHING

(source: Wieckowski, 2013)

9

3

3

2.1284 10 Pa

0.8905 10 Pa s

1000 kg/m

m

l

K

water

o o

3

1 MPa

0.3

30 , 0

2850 kg/m

s

s

E

soil

9 2

1.0 mm

0.474

2.57 10 m

sd

n

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MPM for soil – water interaction

(source: Wieckowski, 2013)

SLOPE EROSION

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Summary and conclusion

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Software tool: Material Point Method

MPM is an advanced tool for analysis of :

• large deformation problems

• 3D dynamic problems (explicit solver)

• multi-phase problems (fully coupled calculation)

• soil-structure interaction problems (no need for interface elements)

• advanced material models (continuum models as in FEM)

MPM is a promising tool for analysis of :

• soil-water interaction problems

• phase transition problems

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Development – generic and applications

sand liquefaction

consolidation

constitutive models (peat)

installation (piles, CPT,..)

borehole stability

sea + land slides

jetting + cutting

scouring / sedimentation

MPM kernel

MPM pre-processing MPM post-

processing

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Joint venture and stakeholders

MPM kernel

MPM pre-processing MPM post-

processing

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Acknowledgement

The research leading to theses results has received funding from the

European Union Seventh Framework Programme (FP7/2007-2013) under

Grant Agreement no. PIAP-GA-2012-324522

This presentation reflects only the author's views. The European Union is not liable for any use that may be made of the information contained herein.

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Questions & Discussion

The material point method (MPM) closes the gap between

soil mechanics and fluid dynamics

…a soil mechanics perspective…