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Limestone Rock Outfall

Limestone Rock Outfall

(OP)
We have a situation where we are designing an underground (roadway on top of it) limestone rock outfall (150'L x 20'W x 4'D) that will transfer water from a pond for treatment. At the end of the rock outfall we will have a culvert to discharge flows downstream. The culvert is easy enough to model but would anyone know how to calculate flows through the limestone rock outfall?

Thanks

RE: Limestone Rock Outfall

If you're talking about lateral flow through porous media, the usual darcy math breaks down once your media is bigger than sand. If you're talking about flow over the stone, as in a stone lined channel, then the treatment usually involves Manning's equation. If you're talking about discharge from a culvert into a riprap apron, and then subsequent flow over the rocks to dissipate velocity, there are some good nomagraphs for that.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

RE: Limestone Rock Outfall

(OP)
No this is strictly lateral flow through porous media. Even 35 year experts at our company are getting stumped by this.

RE: Limestone Rock Outfall

A google search for "flow through rockfill" yields promising results in some books and papers.

RE: Limestone Rock Outfall

Quote:

No this is strictly lateral flow through porous media. Even 35 year experts at our company are getting stumped by this.

If you find an answer, post it here. I've never seen a great treatment of the subject in the academic literature. It's a tough problem. It would need to be studied in the lab, because the assumptions for darcy flow in porous media break down.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

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