bassamyam | 1 Nov 18:34 2007


1-Do you mean by tension (positive value) of the confining
stress..? -p'>= is a sign of liquefaction. I do not think so
particulrly when having a value for the chosion.

2-Strictly stating, liquefaction has something to do with the
constitutive behavior (as I explined) : the soil being liquefied
exhibits at a specific loading (static or dynamic) stage a dramatic
softening (different from the classic softening observed; e.g, in
an over consolidated soil) which marks the liquefaction behavior.
Plot the shear stress-strain curve of a point you claim that it
liquifies : do you notice such drop. No (of course). Anyway
liquefaction mechanisum is a complicated subject (better handled by
a microscopic analysis) which is far beyond from being modeled or
even understood by many of us

Hope this help.

If yes the effective confining stress in ABAQUS is given by p'-u=
(where p is the total confining pressure and u is the pore water
pressure; note u is negative in suction zone; p'is positive in
tension and vice versa) so having negative value for

--- In ABAQUS <at>, ahmed mabrouk <ahmed_badr20 <at> ...>
> Hi Maziar
> So this very short time excitation that needs the inertia effect ,
we are talking about a matter of milli seconds? cuz in my problem
its excavation which will take up to 1 day and static liquefaction
should be expected. SO what do you think?
> Thanks
> Ahmed
> Maziar Mahzari <maziarmahzari <at> ...>
wrote: Hi Ahmed,
> In fact liquifaction is increase of pore pressure due to a very
short time excitation (like earthquake) where drainage of water is
not possible. Therefore the inertia effect is of great importance.
The porouse medium equations (see the theory manual of Abaqus) which
are solved by Abaqus do not include the inertia terms as remarked by
Bassam and hence you can't model the process with Abaqus. ADINA
claims it can model the process but I've no experience on it.
> Hope it helps.
> Cheers
> Maziar
> ----- Original Message ----
> From: ahmed mabrouk <ahmed_badr20 <at> ...>
> To: ABAQUS <at>
> Sent: Monday, 29 October, 2007 6:26:32 PM
> Hi Maziar
> what do you mean by you can't do liquifaction analysis by abaqus?
> Maziar Mahzari <maziarmahzari <at>> wrote:
> Hi Dave,
> 1-How detailed do you want to model the driving process?
> 2-Do you want to use a porous medium for soil? If yes, forget
about doing the driving analysis with ABAQUS. You can't have both
inertia effecs (dynamic analysis) and porous medium (like you can't
do liquefaction analysis with ABAQUS).
> 3-What is the type of soil you are considering? cohesive or
> 4-What is your problem with applying loads exactly?
> I may be able to give you some general guidlines becasue this was
my old time hobby.
> cheers
> maziar
> ----- Original Message ----
> From: Dave <dave_nyc63 <at> yahoo. com>
> To: ABAQUS <at> yahoogroups. com
> Sent: Sunday, 28 October, 2007 10:47:48 PM
> Hi everyone,
> I am a geotechnical engineer working at a company in New York
City. I
> am currently working on a pile driving simulation and using
> this work. Since I don't have an advanced knowledge with ABAQUS
and we
> have a deadline to catch up with, I need someone's help on this
> project. My company would like to pay for the tutoring services.
> Currently, I finished the model, however I have some problems
> applying the loads. If you're interested in helping me and make
> extra cash in your spare time, please let me know.
> My contact info is dave_nyc63 <at> yahoo. com and my cell is 561-385-
> Please feel free to call me.
> Thanks for your time.
> Dave
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