[Geoqus] Plasticity Convergence problem

[hiva at engr.mun.ca]

Hi everyone,

I am working on 3D model pipe-soil interaction. The soil is dense sand and
I am modeling the hardening-softening behaviour of the sand by making a
friction angle, dilation angle and cohesion of the soil as a function of
magnitude of plastic strain. (The constitutive model is Mohr-Coulomb)

Based on available tests I obtained the hardening rule of this dense sand
but unfortunately for this set of parameters the convergence is not
achievable.

This is the error:
SUBSPACE MOHR-COULOMB PLASTICITY DID NOT CONVERGE FOR ELEMENT SOIL-1


By doing  sensitivity analyses, I understand that the convergence had a
direct relation with cohesion and dilation angle and has a reverse
relation with soil young modulus and friction angle.

On the other hand if I want to get convergence I need to do one or the
combination of these: 1-increase the soil cohesion 2-increase the soil
dilation angle 3-decrease the soil friction angle 4- decrease the soil
young modulus.

Does anyone have explanation for this? Why there is such a relation
between my model convergence and mentioned parameters?

I appreciate any help.

Thanks,
Hiva


-- 
Hiva Mahdavi
PhD Candidate
C-CORE
Captain Robert A. Bartlett Building
Morrissey Road
St. John's, NL
Canada A1B 3X5
Tel: 1-709-737-4378 (office)
Email: hiva at engr.mun.ca