MSE Wall Settlement

[BigH]

Just wondering what kind of settlements of MSE walls (separate geogrid walls from "strip" style walls) my colleagues have experienced. Typical and maximum or top three or four maximum.

 

[emmgjld]

I am dealing with an Architectural/Landscaping/Drainage/General Contractor nightmare, about 1 year old.

The differential settlement for walls ranging from 6' to 16' high appears to be 2" in less than 20' and the total settlement may be approaching 6" in some areas. The end of settlement is probably not near. I think only 1 segment of wall is or will be in danger of failure, due to atrocious drainage.

Actually, I am sometimes amazed as to how much abuse these structures can withstand.

 

[fndn]

I Was able to locate the following link:

http://www.rcaanews.org/dowl-1.htmI

I Have not yet had the pleasure with MSE wall design-so can't add any more information.

 

[BigH]

Thought I might get more responses. You see, the RE Walls (yes, the patented system) on our project have undergone some 750 to 850mm of total settlement to date. We've built in stages - the first stage of 4m led to about 250mm or so (remember there is some preconsolidation - even if only "quasi") and then some 400 for the next 4 m and 200mm or so for the next metre. We had to stop taking measurements to put in the base course and asphalt layers. The foundations were provided with vertical wick drains at 1.5m square spacing and stage loading as the shear strength initially was only in the order of 20kPa.
Anyone else have something similar??

 

[jdonville]

BigH,

It shouldn't matter what wall system you use - the foundation soils will consolidate under the applied load just the same. The advantage with MSE is that your differential settlements can be up to 1/100. You could probably get away with more differential if you first construced a wire-faced wall and put the panels on after the majority of settlement had occurred.

I don't know what kind of soil profile you're dealing with here (I'm guessing a single thick, soft, compressible layer with almost 3 ft. of settlements), but we usually calculate settlements due to embankment loads (using Schmertmann or EMBANK) and advise our clients that the expected range of settlements will vary from the calculated number by up to 30% plus or minus for local soils.

I imagine that you could have installed discreet (as opposed to discrete) marks on the facings to act as monitoring points for at least vertical movements of the wall referenced to some elevation datum located far enough away from the wall to be out of the zone of settlement.

Jeff


Jeffrey T. Donville, PE
TTL Associates, Inc.

http://www.ttlassoc.com

 

[BigH]

Hadn't thought of the wire-fenced idea although I did use it once in Vancouver in a temp excavation. We couldn't construct the wall without stage loading. I just thought that 800mm of settlement was a bit on the high side and wanted to know if any others had similar settlements on their walls before. I understand that no many walls world-wide have undergone such settlement. For monitoring, we had settlement plates installed (for the stage construction purposes) and also had marks installed on facing panel to monitor. The tricky part was setting the final panel height - estimating how much more settlement would occur before the friction slab was constructed. We used slip joints every 50 m or so to handle, to a degree, differential. The walls held up remarkably well during the stage loading and large settlements - kept their verticality.

 

[MSEMan]

I've designed an MSE abutment (approx. 12.5m width) that we had to allow for 750mm differential settlement. The bridge was to allow farm access across a new Motorway and was a 56m span bow (steel) girder design. The design provided a deck with very low torsional stiffness so that differnetial settlements wouldn't distress the supersturcture. The existing ground was mine tailings and there was concern that should the old mine works become charged with water the drawdown might create quite severe localised settlements.

Well it did happen following a period of high rainfall - the actual total settlements were more on the order of 700mm total but only 350mm differential but accompanied by about 200mm of transeverse differential such that the bridge was shunted along the sliding bearing in a skew direction. The pinned end of the bridge was over the settlement area. The abutments behaved beautifully and the only problem was spalling of the concrete panels where they rotated into the asphalt verge.

The bridge was reset on its bearings