Longterm Settlement of Uncontrolled (dumped) Fill
Longterm Settlement of Uncontrolled (dumped) Fill
(OP)
I am working with a residential strip footing and a crawlspace foundation wall that is partially supported by competent lean clay soil and partially supported by uncontrolled fill. The fill consists of granular material up to approx. 1" to clay soil and all sizes in between. Fill is generally noncohesive but has some clay in it. I know that longterm settlement is going to be a problem as finer particles migrate into void space even after primary consolidation but I can't find an accepted reference that establishes the potential. Can anyone suggest an accepted reference that establishes the longterm settlement potential of uncontrolled fill.
Thanks,
Thanks,
RE: Longterm Settlement of Uncontrolled (dumped) Fill
Jeff
RE: Longterm Settlement of Uncontrolled (dumped) Fill
Water was a factor here, but everything else in the soil else similar.
On another works I saw about 2" inches settlement on pavement about a year later; however was localized, and due to junk produced by the works outrightly covered by the fill.
Substitution to sound soil was the solution in this, and may be the case in yours, or else make a very stiff foundation or whatever ensures no problem will appear.
RE: Longterm Settlement of Uncontrolled (dumped) Fill
The usual routine for this sort of thing is to dig out the fill and replace it with compacted fill. Or, lower footings to competent ground, or other way to avoid using the fill.
I seriously doubt anyone here will give a recommendation, short of assuming the bearing is very very low and using a very wide footing, but even then, the fill may settle of its own bringing the footing down with it.
RE: Longterm Settlement of Uncontrolled (dumped) Fill
Mike McCann
MMC Engineering
RE: Longterm Settlement of Uncontrolled (dumped) Fill
f-d
¡papá gordo ain't no madre flaca!
RE: Longterm Settlement of Uncontrolled (dumped) Fill
i would however feel quite comfortable in rejecting it and replacing with a controlled fill.
RE: Longterm Settlement of Uncontrolled (dumped) Fill
Thanks jdonville, I checked in the NavFac manuals and find some info to the effect that small movements, even in engineered fills, can be expected for 15 to 20 years.
Again, thanks to everyone, any source that you can point out would be appreciated.
GG
RE: Longterm Settlement of Uncontrolled (dumped) Fill
RE: Longterm Settlement of Uncontrolled (dumped) Fill
If there were cinders or wood products there, that would be different.
Are any of the cracks recent? Dust in them? spiderwebs? Painted?
Occupant reporting any recent noise or noticing change?
RE: Longterm Settlement of Uncontrolled (dumped) Fill
ISBN 1 86081 509 X, pubished in the uk by EMAP, and you can e-mail them at crc-at-construct-dot-emap dot-co-dot-uk.
For a similar situation, check out case study 8, where after 12 years a pump failed, water level rose by 15m and 0.50m of settlement occured near instantly (geotechnically very quickly, well over a couple of months at least).
RE: Longterm Settlement of Uncontrolled (dumped) Fill
iandig, I see the publication for download at BRE Bookshop, do you know if it is available for download anywhere else. I haven't had any luck emailing them regarding US funds.
GG
RE: Longterm Settlement of Uncontrolled (dumped) Fill
RE: Longterm Settlement of Uncontrolled (dumped) Fill
I just checked and found it!
RE: Longterm Settlement of Uncontrolled (dumped) Fill
Perhaps another approach. If the structure has already settled (and presumably caused distress to the structure), why not temporarily transfer the foundation loads to jacks to support the structure, and add water. Sure, you'll have to monitor the foundations and adjust the jacks to accommodate the settlement. And do this until settlement stops. Just a thought!
RE: Longterm Settlement of Uncontrolled (dumped) Fill
RE: Longterm Settlement of Uncontrolled (dumped) Fill
Once you have the density results back you can estimate the degree of compaction and the potential settlement left for the soils. I would suggest a compaction result of 95% will be equal to 0 future settlement. Use 95% as your reference settlement estimator. If you get say a result of 90% compaction I would suggest you could estimate for 5% of settlement is still left to occur. (ie 5% of total fill depth = settlement)
The advantage of a compaction test is it will give you a definite answer to the compaction state of the fill near the footing and if the density ratio is less than 95% it will tell you the site is liable to still undergo future settlements.
The compaction/density test as a settlement calculator will get less reliable as the depth of fill increases and you get uneven consolidation through the fill. In this case you would do a number of density tests all the way down the fill depth to arrive at a more accurate settlement calculation.