Zero water pressure but Permeable

RE: Zero water pressure but Permeable

치훈 송 — Thu, 20 May 2021 09:40:33 GMT

Thanks for your kind advce!

RE: Zero water pressure but Permeable

Dennis Waterman — Thu, 20 May 2021 09:31:06 GMT

Hi,

As you say, it's physically impossible and so it's not possible to calculate that with a groundwater flow analysis because it's not possible to have water seeping into the rock layer without getting pore pressures in the rock layer.
Hence, you either have seepage with pore pressures, or using the Phreatic option and set the rock layer dry to avoid having water pressures against the retaining wall.

With kind regards,

Dennis Waterman

RE: Zero water pressure but Permeable

치훈 송 — Thu, 20 May 2021 09:10:10 GMT

Hi,

I reviewed an excavation with retaining wall under the condition that no water pressure arises in a rock layer, which means that rock layer is "dry".(phreatic level is on the ground surface). "Pore pressure calculation type" was "Preatic" and I made water tables at each phase respectively. I got the water levels of each phase from the analysis by SEEP/W(Geostudio).

Now, I want to review this excavation with pore pressure calculated in PLAXIS. So I will select "Steady state groundwater flow" for the Pore pressure calculation type.

I want to consider seepage in rock layer when calculating change of ground water level during the excavation but I don't want to consider water pressure on the retaining wall in rock layer.

This is contradicting practically but this is what I want to do. I don't know whether this could be modeled in Plaxis, if it is possible, could you please advise?

Thank you so much!!

RE: Zero water pressure but Permeable

Dennis Waterman — Thu, 20 May 2021 08:25:18 GMT

Hi,

How would you physically consider a layer of soil that is dry, but thus have seepage into that layer? If there is seepage into that layer then the layer won't remain dry?
Could you give some explanation on what you exactly are trying to model, so that we can see what would be the solution to do so?

With kind regards,

Dennis Waterman