[Geoqus] Far Field Stresses

[Wouter van der Zee]

Manooch,

 

to incorporate the field stresses, I would use:

 

*initial conditions, type=stress

and

*initial conditions, type=pore pressure 

and 

*initial conditions, type=ratio

 

To keep the stresses in your model, either make your mesh large enough and
hold the outside boundary in 1,2 direction, or use the infinite element as
Jose pointed out. Be aware that you should provide effective stresses, not
total stresses.

 

Please note that from your part of the input file it looks like you want to
calculate time dependent pore pressure (although you call your step
"equilibrium step"). If you want to calculate the equilibrium only them
remove "consolidation, end=PERIOD", it probably makes convergence also more
likely, and you don't have to worry about the permeability of your material.
As soon as you understand your model, you can switch to time-dependent
modeling, and start playing with the permeability (and unit system).

 

Good luck,

 

Wouter

 

  _____  

From: geoqus-bounces+wvanderzee=geomi.com at lists.ruhr-uni-bochum.de
[mailto:geoqus-bounces+wvanderzee=geomi.com at lists.ruhr-uni-bochum.de] On
Behalf Of Manooch Salehabadi
Sent: Tuesday, March 27, 2007 3:52 PM
To: Geoscientific Abaqus User Group
Subject: Far Field Stresses

 

Dear All,

hi and sorry for this simple question , i am just a beginner with ABAQUS.

i am trying to model a bore hole in mohr coulomb media (rock) with plain
strain element CPE8RP, but i do not know how 

to include far field stress in the model?

i have used simple hollow cylindrical model with loading as following to
simulate far field stresses:

 

*Step, name="Equilibrium Step", nlgeom=YES

*Soils, consolidation, end=PERIOD, utol=10., creep=none

100., 14400., 0.144, 14400., 

 

** LOADS

** 

** Name: Far Field Stress Type: Pressure

*Dsload

"Outer Boundary Surface", P, 24.

** Name: Mud Pressure-surface Type: Pressure

*Dsload

"wellbore Face", P, 20.

** 

unit is in MPa , i considered 24 Mpa as far field stress and 20 Mpa as
borehole pressure ,also i have considered

18 Mpa as an initial pore pressure , but i didnot get reasonable results.!

i will be much appreciated for any comments.

Regards

Manooch 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ruhr-uni-bochum.de/pipermail/geoqus/attachments/20070327/1cafeebc/attachment.html>