extending wingwall

[ACtrafficengr]

We're in that lucky area that got hit by both Irene and Lee last year. During those two weeks, the downstream end of the wingwall in the photo scoured. For scale, that is a 10' span pipe-arch.

The existing wall was installed by a maintenance supervisor prone to winging it, so I doubt it was truly designed. It has survived at least three 100 year storms, so I can't really argue with success. It's probably pinned to bedrock.

So, the question is how to repair the scour at the end. As you can see from my handle, this is a bit out of my area of expertise, but I am the only PE in the department. I'd appreciate any constructive opinions.

One approach is to remove the spancrete panels, construct an extension to the cast-in-place wall, and reset the panels. Another might be to place a few pieces of rip-rap in the void, chink them with stone fill, and backfill behind that.

This road only carries < 100 vehicles per day, so expensive repairs (or hiring a consultant) probably will not be cost-effective.

Any suggestions?

PS: Our maintenance guys like those spancrete panels because we can get irregulars and blems from a local precaster for next to nothing.

 

[froude]

Extending the CIP wingwall sounds like a good approach.

Could you squeeze some gabion baskets in there? It's hard to tell from just the picture whether GBs would work for sure or not.

 

[gbam]

There area number of solutions that may be an inexpensive option:
Gabion tied to wingwall, grouted riprap, As you stated an extension of the wing. Wire tied riprap, also known at rock & rail is also a cheap alternative.

Rock & Rail uses railroad rails driven into the bed beyond scour depth. Then galvanized welded wire fabric is tied to the rails and back filled with riprap.