Headwall/Wingwall scour protection 3

[DenverStruct]

If a project requires a toe wall at the end of culvert wingwall, do you think this wall needs to be connected to the slab? Do you think you can just install this toe wall (precast), backfill both sides of the wall, then install precast structure above it? The joint will be connected with ramnek joint sealer. There is really no force on this toe wall. What do you guys think?

 

[JoelTXCive]

I'm interested to hear what others say, but my thought is that you want a positive connection of some sort.

If scour does become a problem and the toe wall is not connected, then it will be more likely to shift, or settle. The toe wall would have to be reset somehow during repairs.

Having it attached gives an opportunity to see scour problems and get some replacement backfill placed. All you would need is backfill though versus having to mess with resetting the toewall.

 

[TehMightyEngineer]

No, you need it to be connected. However, you don't need to connect it as crazily as many DOTs seem to think you do (Really? #8 bars with 18 inches embedment at 12" o.c.?).

The biggest risk I see is the bottom of the culvert end section is a large surface while the toewall is much more narrow; the culvert could easily push the toewall into the soil and then get pushed back upward leaving a gap. This gap would allow potential scour of the culvert end at the turbulent entrance and exit of box culvert under full flow.

So, I've always designed the toewalls to be shipped loose and then installed with rebar dowels and epoxy into sleeved holes in the bottom slab of the box, sufficient for minor lateral loads (box culvert shifting, thermal stresses, etc.) and sufficient to suspend the entire toewall and keep the joint closed.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[TehMightyEngineer]

Here is an example of the toe wall detail we use; doesn't usually have any complaints from the shop personnel or the contractors.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[DenverStruct]

Ian, thanks so much. My questions are:
1. Do you pour that toe wall right side up?
2. How do you embed the dowels to the top of the toe wall?
3. How do you line up the dowels to the pvc?

Thanks Ian, I always try to make the production easier.

 

[cvg]

absolutely connected

There is really no force on this toe wall. What do you guys think?

if the channel scours or degrades 3 feet deep, than that wall may just fall over due to the earth and water pressure force

 

[DenverStruct]

Correct, but technically there would not be scour since you have the wall?

 

[TehMightyEngineer]

Correct, but technically there would not be scour since you have the wall?

Not entirely. Scour is due to multiple factors, piping of the soil would definitely be stopped; however my understanding is the majority of scour is predominantly due to turbulence at the entrance and exit of the culvert during high water flow events.

Ian, thanks so much. My questions are:
1. Do you pour that toe wall right side up?
2. How do you embed the dowels to the top of the toe wall?
3. How do you line up the dowels to the pvc?

1. Yes
2. Post-installed into the toe-wall concrete with epoxy after setting the culvert on top of it.
3. See above.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[cvg]

a local scour hole can develop due to high exit velocity and turbulence. However, bed degradation could also occur, lowering the bed by transporting bed material downstream. that could cause a permanent lowering of the bed downstream of a culvert.

 

[oldestguy]

How'd ya pick that depth? I usually make it equal to the rise of surface during high flows. Same goes for wing walls.

 

[DenverStruct]

Ian, I am always worried detailing something like that in the field. You need really long drill. Plus it is difficult to apply the epoxy?

 

[ACtrafficengr]

During a severe storm, we had an unconnected outlet cutoff wall dragged about 15 feet downstream by the force of the water. I wish I had the picture to show you.

 

[DenverStruct]

It looks like this company does not connect their toe wall.

http://www.michiecorp.com/wp-content/uploads/2014/05/duo-cell-culverts-new-hampshire-800x400.jpg

 

[jayrod12]

Those equally spaced holes at the edge of the culvert look like they could've been used for a post-installed connection.

 

[cvg]

DenverStruct (Structural)(OP)2 May 18 14:39
It looks like this company does not connect their toe wall.

in the last 33 years of working in the water resources field, have never seen a culvert cutoff wall that was not connected nor have I designed one that was. I rarely see pre-cast culverts, most contractors I have worked with prefer to build cast in place. Typical details for box culverts are generally from the state DOT and those details all have a cutoff wall that is structurally connected (and more than 3 feet deep), like this:

 

[DenverStruct]

I wonder if you can replace the cut off wall into an L or T shape. Do you think the DOT will go for that? Then the culvert will just sit on the top of it.

I think for now I just specify a C.I.P. toe wall connected to the precast.

 

[oldestguy]

CVG: Your section A-A shows no footing. However the plan view seems to have one there. I suspect a footing will at least provide a place to set the forms. 6 foot depth looks pretty good.

 

[cvg]

OG
footing may be optional depending on site conditions. If you can get a vertical trench wall to hold, than the concrete is poured without forms or backfill and no footing necessary, however, if the ground is caving, than you need to shore or lay back the trench and a small footing could be constructed and then wall forms set. this would obviously take longer and more expensive.

 

[oldestguy]

I used to be in the WDOT and later with a consultant doing state department jobs. I found too many engineers going strictly by the book out there,which may be good. However, common sense, especially with younger field engineers, was rare. So give them a set of plans like this and you can have problems. Many a contractor has had to get us out there to settle things, and usually they were right.