Mats Karlsson

Implementation of a Modified Anisotropic Creep Model with

Structure for Soft Soils with the use of Physics Builder

Mats Karlsson

Mats Karlsson

Outline

• Introduction

• Creep/settlement in soft soils?

• MAC-s model

• Physics builder

• Implementation

• GUI, input etc

• Validation of material model

• Simulations

• Example of real case

Mats Karlsson

Building on Soft soils

Mats Karlsson

Soft soil behaviourTriaxial system

Oedometer

Mats Karlsson

Modified Anisotropic Creep model with structure

(MAC-s)

MAC-s (reference surface NCS)Based on Grimstad (2009), Karstunen et.al (2005)

”Creep potential surface”

Mats Karlsson

MAC-s model

• Graphical representation of the model

Mats Karlsson

MAC-s model

• Visco-plastic (rate)

multiplier

Rotation of surfaces

Effect of structure

Change in size

Mats Karlsson

Implementation

Why?

• Make it easy to share

• Valid for all relevant

dimensions

• General for any case

• Easy to adopt and change

the equations

COMSOL

Solid Mechanics Linear Elastic Model

Creep node calling MAC-s model user defined model

External stressExcess pore pressure

from Darcy´s law

External stress

Initial stress from other solid

mechanics node

Mats Karlsson

Implementation

Initial stress calculated from another

solid mechanics node (external stress input)

Excess pore pressure calculated in Darcy Law node

(external stress pore pressure input)

-dl.rho*(d(solid.evol,TIME))

Permeability etc

Mats Karlsson

Implementation

Mats Karlsson

Implementation

Mats Karlsson

Simulations

Undrained triaxial test - compression

Mats Karlsson

Simulations – triaxial tests

Mats Karlsson

Simulations – Oedometer test

0

5

10

15

20

25

0 50 100 150 200 250

Axia

l str

ain

(%

)

Effective vertical stress (kPa)

Lab 10m

FE 10m

Mats Karlsson

Real case – Road embankment

Lime-Cement Column reinforcement

Mats Karlsson

Thank you

for

your attention