Pore Pressure results interpretation

[soildynamics]

Hi
I am finding difficulty to interpret some data I got from my analyses .The problem is subjecting the saturated soil to consolidation load in the plane (2D)
I got both pore pressure and effective stress increasing at the same time which is driving me crazy.. can this happens in reality. I have attached the graphs of void ratio, effective stress and pore pressure for the same points under the link. I am 99% sure that there is nothing wrong with my analyses Please take a look
and tell me how do you justify what is happening

http://download.yousendit.com/8A535A54322EE28B

Please comment
Thanks

 

[howardoark]

Your link expired.

In a saturated soil, all of the consolidation load would be taken out as increased pore pressure. The effective stress wouldn't change. As the excess pore pressure dissipaited, the effective stress would rise. That seems consistent with the description of your data.

 

[dgillette]

howardoark - Is that necessarily true in 2D loading where some of the added loading may be taken by shear stresses that are not uniform throughout? It is true in 1D (oedometer) loading, according to theory and experiment, but if there are some elements getting shear loading, they might dilate slightly and show some increase in eff stress even before dissipation of EPWP.

soildynamics - I'm curious whether you get the same effect with a uniform surface load (simulating 1D loading) in your 2D program. (PLAXIS? FLAC?) That would be a good test of your numerical model to try to see if it fits with what you'd expect. Does your constitutive model allow for dilation?

DRG

 

[soildynamics]

Thanks dgillette
I believe 2 D and 3 D have the same behavior trend (governed by Biot theory ) that is very different from 1D (governed by Terezaghi method).
My model doesnot allow for dilation because I am putting Dilation angle=0.
I interpret the simultaneous increase of pore pressure and effective stress as follows: the load is applied in a ramped manner over the analysis time, however, at the observed point the rate of the transfer of the total stress is higher than the rate of pore pressure dissipation therefore the load transferred at that point will be carried by both the effective stress and the pore pressure; i.e both will increase with the progress of time
Please comment if you have any on this explanation.