MSE Wall in water

[Road Guy]

Has anyone seen a MSE (Mechanically Stabalized Earth Wall) in / near water?

I've never seen one but I've got a bonehead consultant telling me there used all the time (In South Carolina) ??

IMO you would have to place the panels so far below the scour line the cost are going to be outrageous..

 

[FLBuff PE]

We design and recommend them, but I don't have experience with them underwater. Are we talking fully submerged? If so, what's the point?

 

[Road Guy]

not fully submered but they want to use them as an end bent about 10' from the edge of a rather large creek with a history of regular flooding.

Its only a ped bridge but they have a 200' span over the creek and IMO they are just half assing it by putting in a MSE abutments so that it ends up being contractor design abutment...

I want them to do an intermediate pile bent with concrete cap and then adjust the span lengths to set the actual end bent out of the flood zone....

 

[FLBuff PE]

I could see an MSE wall working in that situation, but you would need to make sure that scouring doesn't undercut the wall. The O&M, depending on flood frequency, could be pretty high, what with having to replace eroded sediment and what-not. Your design may cost more up front (although MSE's aren't cheap either), but the long-term cost would likely be less.

 

[Dexman PE]

We've got a couple here on my project, and Im the wall project engineer. Granted each of these walls are in low-risk scour areas. We use a CIP wall with caisson foundations for the high risk areas.

Things you have to consider when using them is scour and flooding/draindown. The footing and bottom of wall is at least 2' below the bottom of creek elevation. Several weep holes and a good underdrain system need to be in place. The backfill material has to be a very well draining gravel (we use a #5 ballast rock).

The underdrain system is necessary to prevent underground ponding for when the water level gets high enough to infiltrate the backfill. The water needs a way back out. And the free flowing backfill material helps with tuis too.

 

[Road Guy]

heres part of my problem with there lack of common sense thinking..

this ped bridge is less than 100 feet away from a regional detention facility built due to extreme flooding that occurs in this area, its actually immediately downstream of the new dam that was built, which is only designed to control a higher than average rain event, so this area is prone..

Ive already told them to 86 there design, I would imagine you would have to have this thing 30' into the groun (20' above) and its just not practical to get below the scour line..

dont get me wrong I really like MSE walls, even in areas that have less than perfect soils they work well, it just doesnt make sense here.. me not being a bridge guy an all..

 

[Dexman PE]

Yep, it'd be a CIP wall for me, most likely with caissons.

Another option depending on existing grading conditions (if you have the ability for a top-down construction), would be a soil nail wall with a MSE panel finish. Its constructed like a soil nail wall (nails, shotcrete, etc), but then instead of a finish shotcrete layer, you stand up MSE panels in front (8" gap between back of panel and face of SN wall), then fill he 8" gap with 4500 psi concrete.

Wall looks like a MSE, is armored like a tank, and has the structural integrity of a soil nail wall. Cost is actually comparable to a 10' CIP spreadfooter wall (no caissons). You just need to make sure the channel through there is armored to prevent undermining, or extend the wall below scourline.

Another idea to bypass the below scourline issue is to install grouted rip-rap along the front face of wall (also with weepholes).

 

[Guest]

Vendita Viagra Slovenia Laurgy Cialis suigue Drug Interactions With Zithromax object purchase cialis ribJaini Amoxicillin Moblie Al