Hello!
Im calculating settlement with Mohr Coulumb - Drained, and trying to recreate the following settlement behaviour:
I tried creating 2 different E-modulus by seperating the calculation into 2 phases:First phase with a material with a higher ESecond phase with a material with a lower E
But the result was wierd, I only got a few millimiters of extra settlement in the second phase even tho I chose a really low E.
I also tried (using the same material for both phases) but using "calculation type: Consolidation (19 days)" for phase 1.But the settlement was about 50% lower than "plastic calculation type" and the settlement behaviour looked diferent, heaving at the surface compared to just using plastic calculation:
I tried laborating more with just consolidation, tried different permeabilitys in the soil - which didnt effect the result much (Wierd)??), and I also tried changing the consolidation time, 10 and 1000 days. Then something also wierd happend:
The curves looked identically with the only difference that the x-axis-values was different. I was expecting the curve to have a different shape when using 1000 days. Also, the settlement was a little bit lower when using 1000 days, which is also wierd??But back to my original question, does anyone know how to model the soil behaviour to look more alike to my first graph?
Kind regards
Albin
Dear Albin,
Please check our Wiki article that explains why a Reduction of stiffness does not lead to a change in displacements
In general, you can try using some more advanced soil constitutive models for more accurate soil behaviour, such as the Hardening Soil. However, based on the type of material you have and the properties available you need to choose which one best fits.
You can check all the details of the models offered by PLAXIS in our Material Models manual: Manuals - PLAXIS
As to the plot, it seems that some extremely large steps are considered for both cases. I would recommend some further testing in which you could adjust the default iter parameters and Time step determination to Manual and reduce the First time step of the analysis.
If you need any further assistance, feel free to submit a Service Request. Then, one of our support engineers can help you in detail: https://apps.bentley.com/srmanager/ProductSupport
I got the curve like this using MC model (logarithm of time) at the top point not the center of the clay (curve representing of the clay provided below).
The above is obtained from the top point (0, -0.5) but when considering the center of the clay layer (0,-3.5) which exactly represents the log time curve.
Log time curve
Time curve