chrislaope
Structural
- Sep 15, 2010
- 89
Hi, everyone,
I am involved in a challenging project and need your help please:
A customer has an existing grain bin foundation and he wants to put a new grain bin as high as possible. So I am asked to determine what is the maximum vertical pressure we allow to apply on this foundation. After Analysis, the foundation structure itself is not an issue, but the soil bearing capacity is a big question, the customer now can only find the soil boring test data (done 14 years ago) and I summarized these soil boring data in attached document. No complete soil test report was found (which will usually contain soil engineer’s analysis and the allowable soil bearing capacity recommended by the soil engineer).
My worry is:
From the soil boring test data (see attached document), top 12 feet soil layer has an allowable soil bearing capacity of around 3000psf (I am using Fig 8.10, relation between standard penetration resistance and allowable bearing pressure, in R.F.Craig’s Soil Mechanics TextBook and the raft case), but beginning from 12’ depth, the next 40’ thickness soil layer has nearly no structural strength at all (standard penetration resistance is only 1 to 2 blows/per foot). Because the foundation diameter is 64’, so according to soil mechanics, the pressure at 12’ depth will still has 0.9P (P is the pressure at bottom surface of foundation. Therefore I am worried that if P=3000psf will make the whole 64’ diameter foundation punch through top 12’ soil layer and sink completely into earth (because the next layer has no strength at all).
So my question is: based on attached soil boring test information, what allowable soil bearing capacity can assigned to this soil?
Thanks for your help.
I am involved in a challenging project and need your help please:
A customer has an existing grain bin foundation and he wants to put a new grain bin as high as possible. So I am asked to determine what is the maximum vertical pressure we allow to apply on this foundation. After Analysis, the foundation structure itself is not an issue, but the soil bearing capacity is a big question, the customer now can only find the soil boring test data (done 14 years ago) and I summarized these soil boring data in attached document. No complete soil test report was found (which will usually contain soil engineer’s analysis and the allowable soil bearing capacity recommended by the soil engineer).
My worry is:
From the soil boring test data (see attached document), top 12 feet soil layer has an allowable soil bearing capacity of around 3000psf (I am using Fig 8.10, relation between standard penetration resistance and allowable bearing pressure, in R.F.Craig’s Soil Mechanics TextBook and the raft case), but beginning from 12’ depth, the next 40’ thickness soil layer has nearly no structural strength at all (standard penetration resistance is only 1 to 2 blows/per foot). Because the foundation diameter is 64’, so according to soil mechanics, the pressure at 12’ depth will still has 0.9P (P is the pressure at bottom surface of foundation. Therefore I am worried that if P=3000psf will make the whole 64’ diameter foundation punch through top 12’ soil layer and sink completely into earth (because the next layer has no strength at all).
So my question is: based on attached soil boring test information, what allowable soil bearing capacity can assigned to this soil?
Thanks for your help.