I’m a newer user to PLAXIS 2D Ultimate and I am trying to work through a few modeling errors. The problem I am solving is that I’d like to assess the deformation of a dam for which liquefaction occurs within the foundation soils to understand whether the dam may breach. I’m using a more simplistic model (not the site response/soil behavior approach), but simply assigning a residual strength to a target zone.
My steps are as follows:
- Initial Phase: Set initial stresses using gravity loading without a liquefied alluvium
- Plastic Nil Phase: Remove exess deformations
- FS Check: Compute the FS of normal conditions (mimics LE analysis well).
The problem comes when I try to model plastic deformations with a liquefied zone. In the Liquefaction phases, I change the soil boundary properties of a specific zone to have residual strengths expecting deformation. I also re-set the deformations to zero and I either get a “Load Advancement Procedure” (Upstream Case) or a “Soil Body Collapse (Code 101)” (Downstream Case) error. The pink soil boundary is a liquefiable zone with very low residual strengths. My downstream model is as follows:
The results make sense in that I expect large movements, but I’m not sure soil collapse means that all the movement has occurred or that the mesh can no longer handle the movements.
My upstream model that provides a “load advancement procedure (Code 103 ) error” using typical iteration parameters also makes sense with the LE analysis.
n both cases I would epect the mesh to slump a little more at the downstream toe. My project set up is below.
Anyway, do you have any recommendations on how to adapt the model to better understand the deformation at the toe and remove these two error codes?
Thanks
James
Dear James,
Thank you for all the screenshots. I believe that you are doing quite a challenging project considering you just started with PLAXIS.
The questions you have may require deeper investigation which is why this Forum may not be able to provide you answers to everything you ask. Typically for such complex questions, we use Service Requests for Support so that we can help you further: https://apps.bentley.com/srmanager/ProductSupport
Regardless I can make some comments. You mention that you get two errors, which both point to inspecting Output results to understand where failure occurs. From the screenshots you provided I see a clear failure which can explain why PLAXIS stops the analysis.
I read that you expect the mesh to slump a little more at the downstream toe which based on what I see happens already (scaled up 100 times). You may want to consider adjusting the Numerical control parameters to allow for a few more unloading steps or more iterations to see if it gives you results you can accept.
However, be extra careful and read our Reference manual before changing the suggested default values as you may end up affecting the result.
Considering the deformation and the failure mechanism develop I am not sure you will avoid the Soil body collapse error as there is a soil body collapse in your model.