RE: Hydraulic discontinuity during flow analysis

Faseel Khan — Tue, 09 Aug 2022 17:11:54 GMT

As my colleague mentioned that you can do a steady state or a transient groundwater flow analysis in your model. These flow analysis will determine the water table based on the specified hydraulic boundary conditions.

You can set up the head conditions by going to Flow conditions tab and clicking on a line segment, then assigning a head as shown in the following picture. The part above the soil is assigned a dummy soil and is assigned a Dry condition and in the phases this cluster is deactivated. This prevents any erroneous water pressures on the wall. This is explained in the following article:

https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/45788/external-water-pressures-on-structures-above-the-soil-incorrect-in-2d-connect-edition-v20-solved

In the steady state flow analysis the Ignore Suction option can be checked to avoid any suction pressures from generating.

Once the calculation is completed, you can view the output heads. The results will show full saturation and submerged conditions on one side of the wall as specified above.

RE: Hydraulic discontinuity during flow analysis

Vasileios Basas — Wed, 03 Aug 2022 07:43:18 GMT

Hi Edoardo,

Maybe PLAXIS 2D Tutorial #11 (Flow through an embankment) or PLAXIS 3D Tutorial #8 (Rapid drawdown analysis) will give you some helpful information or guidance for your model. It's worth checking them out as they both deal with variable hydraulic conditions.

Defining different water levels on each side of the wall can be done in different ways. For example, you may create a new water level with multiple line segments placed at the desired elevation (see aforementioned Tutorial examples). Note that for Groundwater flow (steady or transient), the intersection points of the water level with the active model boundaries are important. This is because the program calculates flow boundary conditions in terms of a groundwater head corresponding to the water level. The 'internal' part of the water level is not used and will be replaced by the phreatic level resulting from the groundwater flow calculation. Hence, the water level tool is just a convenient tool to create boundary conditions for a flow calculation. Alternatively, you may work by directly assigning water conditions to soil polygons (e.g. Head, User-Defined or Custom Level conditions).

If you still struggle with setting up your model, you can contact our Support group via the Service Request Manager:
apps.bentley.com/.../ProductSupport