CSP Culvert reconstruction 1

[SMIAH]

A stream flow through 2x48 inches diameter corrugated steel pipes, since 31 years now. Since then and 5 to 6 times a year, there has to be a clean up made in front of them to remove debris and sediment.

They don't have the hydraulic capacity to pass a 2-year peak flow without a significant increase of the WSE upstream (as normal depth exceed the rise of the culvert).

So now, we're planning on a reconstruction with an increase of the diameter (dimension) of the culvert.

First, I was thinking about a concrete box but there is 25 feet of fill over the pipe and a railway over. The first layer of 10 feet under the ground is organic matter. Then a silty clay.

Now thinking about a CSP (Aluminized Type 2) or aluminium pipe.
with a diameter of +/- 10 feet.

I am definately now a fan of CSP - is there another option and should I really exclude the concrete box?

 

[SMIAH]

*not a fan

 

[cvg]

10 feet diameter is somewhat large for a CMP, especially with such high loads. A wider structure such as a concrete box culvert might convey more flow with less of a rise in the upstream WSE. Or try conarch or conspan.

 

[SMIAH]

The soil in place has a low bearing Capacity for a concrete Box.
Well, I am wondering if this is an issue. Will check with the geotechnical engineer.

 

[gbam]

Have you considered a structural steel plate arch? Maybe a concrete precast arch or etc..?

 

[beej67]

I'd call Contech and pick their brains about bottomless arches.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Ryb01]

Hi SMIAH,

Cleaning out a culvert 5 to 6 times a year for removal of debris and sediment sounds like there may be other issues here other than conveyance....will a larger culvert push the debris/sediment problem downstream? Does the downstream ditch/channel/other have capacity? Have you looked into erosion potential downstream? Just pulling straws here.......

 

[SMIAH]

Conveyance is an issue. There's a major increase in WSE and U/S velocity to pass the peak flow through both pipes. Plus, there's a trash rack in front of them.

True that after increasing the culvert dimension, we'll have to take protection measures for erosion downstream.

I'll check Bottomless arch. First, I was thinking about a circular culvert embedded in the ground (10% of height). A 106 inches CSP culvert.

 

[cvg]

a wide, low conduit will result in the least increase in WSE. A multiplate arch or low box culvert would have the lowest profile.

 

[SMIAH]

True, but a culvert with an adequate rise will ensure that the Embedment Depth is adequate for environmental regulation (they're crazy in here) + helping inspection and/or further sediment and debris removal.

Contech arches are pricey, no?

 

[beej67]

My experience with Contech stuff is it's pricey until you look at your other reasonable alternatives. Once you start comparing them to box culverts they start to make sense. Everything's pricey if you want to do it right.

The biggest concern I have with the bottomless arches is foundation scour. Make sure either you take a hard look at that, or your manufacturer does, or your geotech does. Someone needs to look at scour.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[cvg]

multiplate arch is no more expensive than a pipe. Might be cheaper. anything with 25' of fill and a railroad over top will be pricey. A multiplate steel corrugated arch founded on concrete strip footings (with no bottom) might be easier than a 106 inch cmp. No need to worry about compacting the haunches with the multiplate and the strip footings can carry a lot of load. Excavation would probably be less than for your pipe concept.

 

[SMIAH]

Sounds good for Multiplate - Will contact a manufacturer for a price quote.

But scour is an issue too as the bottom material is mainly a silty-clay. Well, the velocities won't be that high for a major event (e.g. 100-year) but enough to be problematic.

Thanks for help!

 

[SMIAH]

For WSE <= Rise and embedment = 10%xRise :

Bottomless Multiplate Arch dimensions = 156" x 81"
compared to CSP (aluminized)dimensions = 106"

 

[Steeleguy]

This option worked for me!

See attached photo

Very cost effective to build!

 

[SMIAH]

What about 25 feet of height fill above and a railroad?

 

[Steeleguy]

These structures are available in arch shapes, an would accomadate the 25' of fill and a train!

 

[SMIAH]

If an engineer want to stamp it

 

[Steeleguy]

Yes sir!
Many will

 

[Steeleguy]

There were large scour pockets on the existing bridge that was removed, Inverted T foundations were designed below the frost line (5' below stream invert). Bearing capacity of the soils were on the order of 1500 psf. Soils engineers and structural engineers designed improved subgrade soil structure, MSE headwall and structure to fit this site, hydraulic engineers designed scour protection.

There were 3 stamps on this project!