I am a newbie of Plaxis. I would like to ask about water condition "Global", "Dry", "Head" & "Interpolate" in 3D
When the model with multi-layer excavation 1 by 1, I would like to ask whether my logic in Plaxis correct or not:
Stage 1: Excavation of 1st Layer
Layer 1: Set "dry" and "deactivate"
Layer 2: Set "head" and Zref = 500mm below 1st excavation level
Layer 3: Set "interpolate"
Layer 4: Set "interpolate"
Soil below Layer 4: "Global"
Soil outside sheet pile wall: "Global"
Hope someone can help me.
In general, whether to use the Interpolate or a specific Head value depends mostly on the soil permeabilities and how the soil is expected to react to the lowering of the water level in Layer 2. Therefore, the information on the project is important to be considered.
When using the Phreatic pore pressure calculation type, it is important to always inspect the computed pore pressure field and whether it is as expected in reality.
Another approach would be to run a groundwater flow analysis either by means of a fully coupled flow-deformation or use the steady-state groundwater flow pore pressure calculation allowing for the program to compute the location of the water level based on the permeabilities, the boundary conditions and the presence of a well, for instance.
A simple example from our tutorial manual can be found here: https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/45558/plaxis-2d-tutorial-03-dry-excavation-using-a-tie-back-wall
A lot of information is mentioned in our Reference manual and specifically on the chapter "Assigning water conditions to soil polygons".
After checking our manual if you still have questions, please submit a service request.
Then, one of our support engineers can help you in detail: https://apps.bentley.com/srmanager/ProductSupport
Thank you for your big help!