What is the most appropriate way to represent flow barriers such as sheet-pile walls?

I have constructed experimental models wherein I use a single row of low-K elements and a double-wide row of low-K elements. In both cases, these barriers are effective in diverting flow. However, in my model of a real site, I find that versions with single-row, low-K barriers allow particle tracks to pass through as if there was no barrier at all.

Is there any plans to add the ability to create a no-flow boundary like the HFB package in MODFLOW?

Dwaine
Dwaine,

for modeling sheet pile walls, please see the topic
[url=http://www.wasy.de/forum/index.php/topic,114.0.html]http://www.wasy.de/forum/index.php/topic,114.0.html[/url].

Currently there is no intention to implement something like the MODFLOW HFB package. In a finite-difference code, it is mathematically quite easy to implement sheet piles (by inhibiting flow from one cell to the other). As in a finite-element code the elements share the nodes, such a simple implementation is unfortunately not possible, and an implementation would have to create additional nodes to separate both sides, possibly leading to additional geometries of the elements.

Best regards,
Peter
Peter, could you check the link for this post, as it now seems to be deleted?

I am interested in the same question - we are currently thinking of just cutting a "hole" in the mesh, as we have been asked to assume that there no flow through a (square) barrier.

Dr Simon Quinn
Principal Consultant
AMEC

Simon,

Unfortunatley the forum has moved a couple of times since I posted the link - so I won't be able to find the target again. However, for sheet pile walls there are basically two options:
[list type=decimal]
[li]Cut a hole in the mesh. Then the wall will be perfectly impermeable. This is only possible in 2D models or 3D models where the sheet pile wall covers the entire depth of the model.[/li]
[li]Use elements with a low k. If applying this option, make sure that the low-k zone is at least two elements wide if you plan to do particle tracking or a transport simulation. Otherwise particles might not 'see' the low k zone sufficiently due to the fact that particle tracking and transport are based on a nodal (continuous) velocity field. [/li]
[/list]
Many thanks Peter for your quick response, this is what we were thinking.

Best Wishes,
Simon

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