riprap design for pump station discharge basin apron

[pinkpig]

any good equation for estimating riprap size around pump station discharge basin apron? The discharge basin itself is concrete one, and from there the discharged water will be spilled out to riprap apron/chute.

I guesss I can not use the river bank revetment protection equation since there will be a lot of turbulence flow involed in my case.

thanks.

 

[gbam]

pinkpig check FHWA's HEC14/HEC15, or you can base it on the shear stress and velocity. What mnagnitude of discharge are we talking about, outflow velocity and depth?

 

[pinkpig]

Thanks for your reply, gbam.

HEC-14 or 15 are good references, but are they suitable for Pump Station discharge apron? here I can see a little bit complexed conditions: turbulence, pressurized flow to open channel flow,...

I am new to Pump Station design, anyway, in my case, the discharge is 800 cfs. What do you guys do usually for this type of design?

 

[beej67]

You want to design it based around velocity, not flow rate. Use good ole college fluid mechs to determine your velocity. If you've got high velocity discharge out of a pressurized pipe, I suggest a concrete splash pad be your first point of contact, then riprap around the edges. If you don't feel like mucking through all of the above listed HEC documents, some state erosion control guides have nomagraphs you can use. Check with your state.

ex:

http://www.gaepd.org/Documents/esc_manual.html

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[cvg]

800 cfs pumped discharge?!!! sounds high to me. could that be 800 gpm?

you need an energy dissipater, not a splash pad. suggest an impact type stilling basin. riprap would be at the end of the stilling basin.

 

[beej67]

Oh wow, I sure misread that. 800 cfs is the kind of flow I'd expect at the 100 year storm under a small to medium sized bridge. He must mean 800 gpm.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com