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Cutoff Wall In Concrete Transition

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It's been a loooong time since I have dealt with box culverts, but from what 
I remember, a cutoff wall at the outlet is absolutely necessary.  In addition 
to the box culvert constricting flow, and thus requiring the flow to be 
faster thru the culvert to move the same amount of water, the concrete invert 
is always smoother than the natural channel upstream.  When the water exits 
the culvert, it will pick up material at the end of the invert and move it 
downstream.  Without a cutoff wall, the culvert invert will be undermined, 
and without support, it will eventually fail.

The cutoff wall at the downstream end should be at least a metre deep; at the 
upstream end, about half that.


A. Roger Turk, P.E.(Structural)
Tucson, Arizona


. > Fellow Engineers

. > a week ago i had posted a question on the LIST about the afore mentioned 
. > subject, unfortunately i am yet to see any response on the same. Iam 
. > posting this question  again with a hope some expert will find time to 
. > respond appropriately. 

. > " iam designing & detailing a buried concrete box channel for storm water
. > drainage. It has a concrete transition both at inlet & outlet. From my 
. > experience i know every concrete transition should have a cutoff wall at 
. > the end. There is a resistance from some quarter for putting a cutoff 
. > wall in the shop drawing. According to them its not necessary. i seek 
. > opinion of the experts, on design of hydraulic structures, on this issue. 
. > Is cutoff wall necessary or not in a concrete transition for a cross 
. > drainage structure?" Thank you all in advance.

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