Sizing Rip-Rap apron at Blow-off
Sizing Rip-Rap apron at Blow-off
(OP)
I need to size a rip-rap apron for a 10" blow-off for an 18 water transmission line. The flow at the blow-off is 3.7 cfs, which calculates to around 8 fps, but the line has 120 psi of static pressure. I can't use a gravity flow calculation because of the static line pressure.





RE: Sizing Rip-Rap apron at Blow-off
That's a lot of water.
I don't know of any calculation that would support this but, I suggest you use the biggest rip rap available. In the northeast, it is commonly called "crusher run."
Also, you'd better be aware of where the water is headed, even after you have dissipated the velocity.
RE: Sizing Rip-Rap apron at Blow-off
RE: Sizing Rip-Rap apron at Blow-off
Rip Rap sizing is based on velocity, and based on the characteristics of the receiving body of water. (tailwater condition / etc) It will vary by location. In Georgia, we use this:
http://www.gaepd.org/Documents/esc_manual.html
Page 6-181.
If you want to get fancy, use this:
http://
You know your velocity, work from there.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com