Thick back fill
Thick back fill
(OP)
I need to back fill a 50'x50'x12' (deep) pit and build a pre-engineering building. The max load from each column (Total of 8) is 50 kip. I specify the select structure fill as backfill material. Backfill are required to be compacted (95%)every 8". However, I am still afraid that this thick backfill will cause exessive settlement. I do not have a lot of this kind of experience. Is any engineer here can give me any suggestion on how to prevent the settlement in this situation? Thank you very much.





RE: Thick back fill
RE: Thick back fill
RE: Thick back fill
RE: Thick back fill
95 percent of Modified Proctor is a common very conservative requirement. Now let's say your column load is 500 kips. Then you might measure a slight settlement, but still well within usual tolerances.
Another thing, those metal buildings can take all kinds of distortion. Does the manufacturer give any limits to differential settlement?
The main trouble I have seen with them is excessive snow loads popping the bolts, but no catastrophe with some major footing settlements (like 1.5 ft. in 200 ft.).
RE: Thick back fill
RE: Thick back fill
By the way, if I assume the subbase under this thick back fill is strong enough. What kind of bearing capacity I can expect for this 95% compacted select structure fill (NYSDOT spec. item 203.02)? I assume 4000 psf to design footing. Will it be too conservative? I cannot find any info about that.
RE: Thick back fill
Maybe a local geotech might be contacted in the case of a written recommendation requirement.
What comes from here obviously are opinions based upon limited data, but usually from experienced engineers.
RE: Thick back fill
RE: Thick back fill
Can you forecast this in advance? Not likely. DM-7.2 (p. 39) gives some data on the anticipated properties of compacted earth fill and you'll see some typical values of compression that can devleop in various compacted soil materials.
So, I'm not sure it's a non-issue, but it may be. I'm pretty sure it's not a foundation issue, however.
f-d
¡papá gordo ain't no madre flaca!