Scour - shocking results
Scour - shocking results
(OP)
The bridge has overbank flow forced back in the river channel by the bridge approach embankments. Based on the Live-bed scour in the contracted bridge opening, the maximum scour depth is ... 15 feet.
The D50 is 1.5 mm and the flow rate is almost 10,000 fps passing through an opening of 100 feet.
I know that the equation is conservative according to some reference (Richardson and Davis, 1995) because it assumes a long contraction where uniform flow can develop. I just think that this maximum scour depth is not... reasonable.
Something I should do before sending the results to the Structural Engineer?
The D50 is 1.5 mm and the flow rate is almost 10,000 fps passing through an opening of 100 feet.
I know that the equation is conservative according to some reference (Richardson and Davis, 1995) because it assumes a long contraction where uniform flow can develop. I just think that this maximum scour depth is not... reasonable.
Something I should do before sending the results to the Structural Engineer?





RE: Scour - shocking results
RE: Scour - shocking results
RE: Scour - shocking results
RE: Scour - shocking results
RE: Scour - shocking results
I just thought it was overly conservative but you bring good point by saying that the scour will be filled back in.
I'm just keeping it back before sending it to Structural Engineer. I know that he never faced something like this before.
100 feet!
RE: Scour - shocking results
RE: Scour - shocking results
RE: Scour - shocking results
The embankment scour equations are outrageously conservative. Here we specify embankment scour protection (very successful) and ignore the scour data for embankment scour. Pier and contraction scour we take very seriously, and we assume channel migration and armor piers the same on the overbanks as the channel.
We also have strict rules regarding how much backwater is allowable: 0.14 ft is allowable without having to purchase flood easements. I would expect substantial backwater from cramming 10,000 cfs through a 100-ft wide opening... not to mention the 500-year storm.
RE: Scour - shocking results
We do ignore embankment scour as well.
Just to mention: that flow rate of 10,000 fps is the 500-year storm (well 1.7 x 100-year).