Automate the packing process in Plaxis - Plaxis 2D / Plaxis 3D

Automate the packing process in Plaxis


YouTube-tutorial that explain the creation of .bat files for automating the packing of Plaxis-projects. The option of automatically pack your Plaxis 2D or Plaxis 3D files provides both energy and time saving for the user.


The video explains the lines needed in a .bat files and can be applied to all Plaxis files. However different versions of Plaxis as well as the 2D/3D programs needs different file-endings to work. These can be easily checked by looking at the files you want to pack.


Link to video: Packing Plaxis 2D and Plaxis 3D projects

Common mistakes made in Plaxis

There are a lot of mistakes to be made when modelling in Plaxis. A term often adopted is shit in shit out or something similar and it is completely right!

The lack of understanding can result in serious consequences and software like Plaxis is not to blame. Except in rare occasions where the software is actually wrong the answers given will be a direct result of the input/instruction given by the user. This problem is not helped by the simplicity of Plaxis where someone without understanding quite easily could; create, run and obtain results from a model and therefore believe that everything is OK and correct.

It is vary important to check input, assumptions, model and output and more importantly have someone else check. The problematic thing is that even thou everything is checked multiple times by different people, things can get overlooked.

Here are a few things where people tend to make mistakes in Plaxis:

Generating initial conditions with k0-procedure
Engineers often run the k0 without thinking of what the k0 procedure does to generate the initial effective stresses. The k0-procedure is only correct when all the geometry of the ground surface, the ground layers, and the ground water table are horizontal. If this is not the case the k0-procedure will lead to the existence of unbalance forces or non-equilibrium of initial forces.
 

Changing (SUM)M_stage in a faulty manner
In some cases the user can choose to change the Sum M_Stage to a value smaller than 1.0. If the user does this it is important that the user knows what happens. Say that the goal is to run 50% then 25% and then the final 25% the way to do this is to have the M_Stage set to 0.5, 0.5 and 1. 50% in the first stage, 50% of the remaining 50% in the second stage (i.e. 25%) and 1, 100% of the remaining 25%. (This is explained in more detail in the Plaxis Tunnel Webinar. LINK)
 

Switching back and fourth between Mohr-Coulomb and Linear Elastic material
If the switch is made for a material from Mohr-Coulomb material model to Linear Elastic the user needs to pay attention to the input-parameters. These can change between every flip that is made and should be checked so that they correspond to the values that the user wants to use.

Putting Interface Elements where they don't belong
The user should check if the interfaces used actually obtain the results that is sought. For example interfaces on node-to-node anchors and embedded beam rows are sometimes inserted.

Not Checking the undrained shear strength when using Undrained (A)
The shear stress values have to be checked so that they do not violate the undrained shear strength from soil or laboratory tests.

Dilatency angle when modelling with Undrained (A)
Dilatency angle for Undrained (A) should be used with care. Plaxis recommends that the dilatency angle is set to 0 in their manuals. Positive angles may lead to unrealistic values in tensile pore stresses i.e. unrealistic values of  shear strength. Negative angles may lead to unrealistic values in pore pressures and therefore behaviour.

NEW Plaxis Webinar - Embankment on Rigid Inclusions

Interesting webinar focusing on the modelling of rigid inclusions as Embedded beam elements under embankment. The reason for the rigid inclusions are layers of softer materials that have to be reinforced to enable the embankment to be built on top.

This webinar is a good introduction to these kinds of problems with a live demonstration where the full model with embankment and two types of embedded piles are created and run.

The introduction part of the webinar was sufficient to understand the creation of the model and the trick used for the embedded beam row where a small part of the beam is created in the material above the connection-point to overcome the problem with the fixed connection. Instead of the fixed connection, an axisymmetric model is created with the same material for one beam only. The correct skin friction for each beam is extracted and used for the connection-part of the beam in the layer above.

Overall, the Webinar was good and well built with a good combination of introduction/theory and axial modelling. The amount of information however does not enable a non-experienced user to create their own models.

With the amount of Tutorials etc. for Plaxis being so low, it is very good that Plaxis has these webinars.

As soon as the webinar is uploaded, a link will be posted.

Also a teaser for Plaxis 2D 2016 has been uploaded on the official Plaxis channel. Link in the News section