Gabion wall repair - toe reinforcement

[McStorm]

Does anyone have experience with repairing gabion walls that have rusted and failed at the bottom? We have many sites throughout the St. Louis area where the bottoms of the baskets have rusted and opened, even with the coated baskets, because the coating gets knicked during construction or by gravel flowing along the stream, then the road salt takes care of the rest. In some places, the rocks have washed out and now the upper baskets are "hanging", but have not failed. In these locations, we were hoping to repair the toes, but with something other than gabion wire, since it will likely fail again. One idea was to form a concrete toe with a flowable fill, but not sure if that would be permittable or if it would have enough compressive strength to hold the weight from above.

Any help is greatly appreciated!

 

[cvg]

instead of trying to repair holes, one of the easiest ways is to place a layer of wire mesh over the top and connect it with hogrings or lacing wire to the existing wire mesh (at good, un-damaged locations). Rails can also be driven to help support the wall from falling. However, this needs to be done before rust gets too bad or before all the rocks come out. It is difficult to "stuff the rocks back in". You could pressure grout the bottom layer of rock and probably extend the life of the structure considerably as well as strengthen the base. I can't comment on foundation strength, not having seen details of the installation. However, I hope your walls base extends below grade and if so hopefully below the scour elevation.

 

[McStorm]

Thank you, cvg!
Unfortunately, most of the rocks have washed out. The stream has a bedrock bottom, so the baskets do not extend below grade. The wall is approximately 6 to 9 feet high. How would you drive rails? Something thin enough to get through the basket holes, I expect?

 

[cvg]

well, driving rails into bedrock was not something I originally considered. This is typically done in alluvial streams, above the bedrock elevation. You might have to drill in rock anchors.

 

[McStorm]

Here is a photo showing one problem site. I don't know why the upper baskets are still level, but I assume it is due to something anchoring it into the slope. I believe these were built in the 1980's, and there are complaints of failures in 1997, where they did come back and form a concrete toe, but the environmental regulations were not as stringent back then.

We were theorizing that we could isolate the area with sandbags or something less permeable and pump out the water until the grout cures. As you can see, there is not much base flow. The problem would be if there was an unanticipated rain event.

Any other thoughts besides grout/concrete?

Thanks again!

 

[cvg]

I don't see a lot of rust there and the baskets look like they are in pretty good shape. However, I do see some issues with improper lacing, upper right corner is a large enough opening for a rock to go through and lower right looks like something broke the wire. Maybe a log floating down the river snagged and broke it. You might be able to construct a gabion buttress in front of this area to stabilize the wall. Place an additional row of 3x3 along the toe and tie it to the existing. Use double layer of wire since it is at the invert of the river and subject to more erosion and corrosion than the higher layers.

 

[McStorm]

You don't see that the bottom row of baskets is open and all the rocks are gone? Maybe the picture resolution is not good. Here's another one.

 

[cvg]

So there is an entire 3' thick row of baskets completely gone? It wasn't clear in the first photo. If you can install concrete or grouted riprap that may be the best method. Forming may be your biggest challenge.