Accounting for countersinking in culverts in HY8

[Jajosk]

I need to determine the diameter of a proposed culvert for a given roadside ditch. In HY-8, how do I account for counter-sinking of culverts below stream bed:
a) inlet to 40% of diameter,
b) outlet to 20% of diameter

Thanks

 

[cvg]

do you mean a drop inlet? or buried invert?

 

[Jajosk]

The kind of depression I mean is one used for fish passage. Such as this one -

http://www.fws.gov/midwest/ashland/images/FY08/08_Dec_13_w.jpg

I believe it is a "buried inlet". Would that be correct? Thanks

 

[Jajosk]

Also, out of curiosity - does sinking the barrel as shown in the link I have in my last post do something for culvert anchoring (i.e., uplift force @ inlet), or is the surcharge weight insignificant?
Speaking of anchoring, is there any standard drawing for just a toe plate anchoring for culvert ends (not as part of a headwall arrangement)?

 

[ACtrafficengr]

Do you have the latest version of HY-8? In 7.2, it's called "embedment depth."

It's measured in inches, and assumed to be constant, not more at the inlet than outlet like you mentioned. Maybe you could check for inlet control at 40%, and outlet control at 20%, and use the worst case.

 

[ACtrafficengr]

At 100 lb/ft^3 or more, I'd assume you'd get a lot of ballast from the fill.

On the other hand, my state has had four 100-year events in 16 years. Maybe you should assume a storm has blown all the fill out as a worst case.

NYSDOT has a sheet showing toeplate extensions on end sections. Does this help?

https://www.dot.ny.gov/main/busines...ings/standard-sheets-us-repository/603-02.pdf

 

[cvg]

the photo in the link seems to show little or no cover over the culvert. without headwalls, pre-fab end sections or anchors, the culvert is at risk of movement during a large flood. this is a poor design to copy. I agree that during a large flow, the material in the bottom of the pipe will be scoured out due to high velocities in the culvert and you will have no ballast.