CMU Retaining Wall leaning forward 1

[nmdeveloper]

I'm investigating a wall that is approximately 300' long and 10' high. the wall is leaning out away from the retaining side by 1/2" - 2 1/4" inches. The contractor is claiming that 2" out of plumb in 10' vertical is an acceptable industry standard (this is in New Mexico, bear with me) my position is that there is no allowable tolerance for being out of plumb. I'm having a hard tme finding anything published that states one way or the other. Beyond common sense, does anyone know of a resource to answer this?

 

[hokie66]

I don't know of any such tolerance. I assume as you are talking to the contractor who built it that this is a relatively new wall, and if that is the case, he is just trying to avoid responsibility.

My guess is that either the footing is too small or the reinforcement is not in the right place. Either way, the leaning will probably get worse.

 

[cvg]

how about federal uniform guide specs? see the attachment

 

[civilperson]

1" of rotation is normal, necessary and planned for by battering the face. 2" is probaly OK if no further movement occurs, (unlikely).

 

[hokie66]

cvg's reference would give about 1/4" tolerance, but I think that is for built out of plumb, not rotation.

civilperson is correct in that the face should have been battered, but it is seldom done with CMU walls. If this movement has occurred in a short period of time, it is beyond normal.

 

[cvg]

sounds like the contractor is still on the hook for this so either it was built out of plumb or started leaning shortly after it was constructed. For the second case, it may have been designed incorrectly. Either way, I think the tolerances would still apply during the contractors warranty period.

 

[hokie66]

Designed incorrectly or built incorrectly. If the contractor built it to a poor design which wasn't of his doing, he is not responsible. If he built it poorly, he is.

 

[msucog]

i'm fairly certain that aci and/or ibc (not sure which one) mention construction tolerances. i suppose the trick would be figuring out if it was built out of whack and hasn't moved at all OR if it was built perfect and is now moving OR was built a little out of whack and is moving. i suggest you take measurements (from top to near bottom) with a plumbbob at intervals along the wall and record the data. come back at some time later at the same locations and see if it moves. if you know how old the wall is then you might be able to ballpark when the readings will provide indication that the thing is still moving (if it is indeed moving). you might also revisit the paper trail of inspection reports (footing, rebar, drainage materials, backfill materials, etc), foundation reports, design dimensions, etc.

realistically (for construction tolerances...not movement) from my perspective, a "good" wall is within a 1/2" or less and an "kinda sorta okay" wall is 1" or less for a 10' height. however, i have seen fairly strict construction tolerances from the EOR for CIP retaining walls.

and never take a contractor's word for anything...whether you actually know the answer or not...

 

[hokie66]

Just for what it's worth I recently investigated a similar situation and found the reinforcing in the wrong face of the wall.

 

[cvg]

hokie66 - we also investigated the same situation with the rebar in the compression face not the tension face for a bulging concrete retaining wall. Other construction oddities included foundation steel only tied into the wall every 7 feet. However, it was built 95 years ago and still standing. We will probably leave in place and buttress it...

 

[hokie66]

cvg, yes, there are a lot of walls which serve perfectly well in spite of poor construction. Some unreinforced brick walls actually do well for a long time, but then start to lean. Sometimes there is no justice.

 

[nmdeveloper]

Thanks everybody for responding so quick, I found that several states publish their construction specs for public works online. The consensus seems to be 1/2" - 3/4" out of plumb in 10' vertical is acceptable. cvg and hokie66 are both correct, we did find that the reinforcing was on the wrong side of the wall.

 

[hokie66]

In which case, the wall will eventually fall over. There are only two options: pull the wall down and start over, or drill through the wall in the top part and install tiebacks. Well, there are other options, but these two would probably be the ones you want to consider.

 

[Hagops]

Has anyone checked the type of backfill that was used behind the wall,and the method that it was placed?? The moisture content of the material could create "bulking" of the soil if it is placed "dry" and then gets saturated.

 

[ruready]

Is it leaning or did the wall rotate? Most out of plumb issues have nothing to do with the masonry but the footing settling, compaction issues... At least thats what our issues have been

 

[Riggly]

I see that you already found a very likely cause of the problem, and I think we can all learn from this scenario- specify the tolerance in the specs. In this case you could easily refer to the specs which the Contractor would have to adhear to. Personally, if I see a wall CMU wall rotated 2 1/4" inches in 10ft, I would be very concerned. I notice one case with a MSE wall that the wall started tipping forward after the contractor was operating a crane close to the edge of the wall.

 

[MSEMan]

C'mon guys - back to basics:

It doesn't matter in which face the wall is reinforced, that could not explain a lean in the wall, maybe cracking, but not a lean. The wall is rotating, apparently about the toe, so it is a global failure rather than (or additionally to)a structural one. My first guess would be that the fill used behind the wall is significantly weaker, or more poorly drained, than assumed in the design. My second guess would be that the foundation soils are weaker than assumed and aren't strong enough to support the toe pressures.

 

[hokie66]

MSEMan,

This question has been asked and answered.

Back to basics indeed. If the reinforcement is in the wrong face, as the OP has found is the case, the wall certainly will lean.

 

[Riggly]

MSEMan, It is very possible for a CMU wall to lean forward on good soil. From a structural perpective, this type of wall may be considered flexible at the connection to the base, and with the reinforcement on the wrong face of the wall, the wall would even be more susceptible to that type of defect.

 

[apsix]

"this type of wall may be considered flexible at the connection to the base"

I find it difficult to design with this assumption.
I always assume a cantilevered wall has a fixed connection to the base.

I know the question has been dealt with, but I wouldn't be suprised at 0.5" movement at the top of a 10' wall.