Is it possible to model negative pressures in SEEP/W

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MarkBiesheuvel
MarkBiesheuvel Posts: 1
in GeoStudio

Hi All,

I'm working on a model where I need to actively extract water from the bottom of a 10m high sand column by applying suction. The goal is see how the the saturation changes over time.

I've applied a constant pressure head of -5m at the bottom to accelerate the dewatering process. I'm using the Saturated/Unsaturated Material model for sand.

The result is that at the boundary the pore water pressure becomes negative and desaturated (I assume because of the VWC function). As the boundary is on the bottom of 10m of saturated sand, there should be no air available to actually desaturate the soil. However SEEP/W does do this and as a result permeability of the sand close the the boundary reduces significantly. Which leads to an even lower flowrate then when I use a zero pressure BC at the bottom (which does not cause this desaturation effect).

How can I solve this issue, is the SEEP/W capable of handling negative pressures in this manner or is a negative pressure always coupled to a desaturation? Is there a workaround?

Possibly there is a different model I can use for this type of calculation?

Desaturated column.jpg

Thanks,

Mark

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