Define Pore Pressure for Flowknot Calculation

Hi everyone, Is there any way to define water table for flowknot flow calculation by using CAD geometry (let 3DEC calculates hydrostatic pressure from this) ? I want to simulate hydromechanical coupling for slope stability analysis.

I prefer result like this one.

Thanks, in advanced.

1 Like


From my experience, there is no ready-to-use functionality for this application.
The trick would be to use Fish for manually looping through the flowknots, computing their distance from the water table and finally estimating the pore pressure.
I’m pretty sure you can create a geometry object from a CAD import, and luckily the geom.set.raydist(g,vpos,vray) Fish function gives the distance from a geometry object: g would be your water table, vpos the flowknot positions and vray the upward vertical vector (0,0,1). I’m not sure as to what happens when your position is above the geometric set (and hence when no intersection can be found), you might have to first select only the flowknots below the water table.

Good luck with your scripting!


1 Like

Thanks for suggestion!

You can do this much more simply. Just import a geometry (dxf or stl) and use the command BLOCK WATER SET. This will do what you want without FISH. You just need to specify fluid density and gravity before you give this command.

1 Like

I’m not the OP but thanks for the hint, I wasn’t aware of this command!

1 Like

Thanks for your guidance. I have just tried to use block water command, it was good for import water table plane and applied pressure in plane but in jointed flow run with hydromechanical in 3DEC (fast flow), displacement and factor of safety in my model is too low (less than 1). I cross check about this and find that pore pressure in joint plane was not fixed. Do you have any boundary conditions or other suggestion for me to solve this. Thanks, in advanced!

Please send your data file(s) to technical support and we can investigate.

Further question, is there any way to simulate fast flow (fully hydromechanical coupling analysis) by initializing pore pressure from a water table plane from CAD and fixing pore pressure in some way like a balancing recharge and discharge for slope stability analysis? I have tried to simulate this, but my pore pressure loss due to fully HM simulation. Is there any way to prevent pore pressure loss?


1 Like

Dear Jhazzard,
But if I use this command, deformation in joint plane due to hydromechanical response will not occur because pressure is fixed. Is there any way to solve this? Thanks, in advanced.

Well, you can still get deformation due to inflow and outflow (changes in fluid volume), even if the pressure is constant.

1 Like

have you used it any any examples in which I can find in documentation BLOCK WATER SET.?

this command command FLOWKNOT FIX PORE-PRESSURE ?

Simple example is here. Note that FLOWKNOT APPLY P-P is the same as FLOWKNOT INI P-P + FLOWKNOT FIX P-P