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12 January 2017
Soil model interface in Anura3D
Dr Alexander Rohe
Dynamic equilibrium liquid
Dynamic equilibrium mixture
Mass balance liquid
Constitutive equation
( )ll l l s l
npkg
r r= Ñ - - +v v v g&
( )1 s s l ln nr r r- + = Ñ × +v v σ g& &
(1 ) vol volls l
Kp n nn
e eé ù= - +ë û& &&
=σ D εg& &g
soil skeleton velocity
liquid velocity
porosity
solid density
liquid density
density of the mixture
liquid pressure
total stress tensor
strain tensor
tangent stiffness tensor
liquid bulk modulus
gravity vector
lvsv
nsr
lrr
pσεD
lKg
MPM is acontinuum-based
method
Governing equations (coupled 2-phase problem)
strain [-]
0
100
200
300
400
500
600
700
0 0.1 0.2 0.3 0.4 0.5 0.6
Relative density = 80%
Relative density = 63%
Relative density = 30%
s1–s2
[kPa
]
0.1 0.2 0.3 0.4 0.5 0.6
advanced material models can depend on:plastic strain, stress and strain rates, density, …
handling the history of state parameters is essential
triaxialconditions
1s
1s
2s2s
Constitutive model
Current constitutive models in Anura3D
• Linear Elasticity• Mohr-Coulomb Elasto-Plasticity• Mohr-Coulomb Elasto-Plasticity (Teunissen)• Mohr-Coulomb Strain-Softening• Mohr-Coulomb Suction Dependent• Isotropic Cone Hardening• Hypoplasticity Sand (Von Wolffersdorff)• Original Cam-Clay (Schofield and Wroth)• Modified Cam-Clay (Burland)• Nor-Sand (Jefferies)• Unsaturated Nor-Sand (Fern)• SANISAND (Dafalias and Manzari)• User-defined soil model (UMAT/VUMAT)
at different levels of:availability,validation,
testing,documentation,
robustness,reliability,
applicability,…
General constitutive model
Approach for user-defined soil model:
• external library (DLL) containing constitutive model
• standardised user-defined soil model interface (UMAT format)
• standardised material parameter input
• can be used in several environments (e.g. Abaqus, Plaxis, Tochnog, …)
Benefits
• standardised software interface (UMAT format)• modular set-up, well-documented• transferable to other (commercial) software products• development is software independent
• validation and testing possibilities• by e.g. using in other software, also single-element test
• straightforward implementation (using Fortran)• no specific Anura3D code knowledge necessary
• straightforward input of material parameters• standard interface in GiD available
• includable in material models database• automated testing and documentation
UMAT/VUMAT interface
www.soilmodels.infoUMAT+VUMAT routines,
open source database of models, documentation
UMAT à used in Abaqus/StandardVUMAT à used in Abaqus/Explicità for differences and interface: Bienen et al., 2014
Full definitions of the UMAT and VUMATrequirements and conventions are detailedin the Abaqus User Subroutines ReferenceManual v6.12 (Dassault Systèmes, 2012)
Example UMAT
Provide DLL for Anura3D
To use the external user-defined soil model, copy the DLLUMAT_mymodel.dll into the calculation directory together with theexecutable of Anura3D and the input files (CPS_001 and GOM)
`
Interface for user-defined soil model
`
`
Input file in ASCII format
automatically generatedwhen selecting “User-defined Soil Model”as “Material model solid” in pre-processor GiD
name of the external DLLcontaining the
user-defined soil model
array of 50 valuesspecifying the material
properties
Triaxial Test Simulation
Linear Elasticity
Triaxial Test Simulation
Mohr-Coulomb
Summary
• user-defined soil model interface available in Anura3D
• develop models in UMAT/VUMAT format
• test and compare UMAT with other (FE) software