Reno Mattress
Reno Mattress
(OP)
For a trapezoidal channel with a flow of 1050 cfs and a velocity of 8 fps what is the minimum bank slope for a reno mattress
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RE: Reno Mattress
RE: Reno Mattress
where v=velocity,
n= Manning's roughness coefficient (0.018 for concrete)
R= A/P
A= Area of flow
P= Wetted perimeter
So you see it depends upon the shape of the cross section also.
RE: Reno Mattress
You should be able to install the mat at 1:1, I wouldn't go steeper.
8 fps is fine if the thickness is over 6". In PA, USA you can use Reno mats up to 18 fps, but watch shear stress = 62.4 x flow depth x bed slope. It must be 8.35 lb/sf or less, and at that flow rate, shear will probably limit design.
RE: Reno Mattress
Another alternative to reno mats is 3x3xL gabions or just dumped/grouted riprap. Typically the mats are more expensive than grouting riprap.
RE: Reno Mattress
Thanks
RE: Reno Mattress
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RE: Reno Mattress
If you want steeper, construct a bank using stacked gabions. Stack them either at a slope or offset each layer to form steps. Maccaferri provides a wealth of design information and examples. Ask your local supplier for the literature.
RE: Reno Mattress
If the question is what are the slope limitations for reno mattress, are we talking about channel sideslope or bed slope? I think the channel sideslopes are not as much an issue as the channel bed slope. You're more likely to have problems with shear stress on the bed than on the sideslopes. I've used reno mattress and gabions a lot for landfill downchutes and was surprised recently when a manufacturer told me about the limiting bed slopes for these systems. I recall they were uncomfortable with even a 4H:1V bed slope. Companies like Maccaferri have good tech support and may be able to offer assistance.
One final thought- there are alternatives out there like fabric-formed concrete and concrete-filled geoweb.