Table from Foundation Analysis and Design by Joseph Bowles

[countyreviewer]

I looked up a soil classification for an area as "SM" Indianola Sandy Load. The talbes I can find say the bearing capacity is 2000 lbs, but I had another engineer say that the Foundation Analysis and Design book by Bowles states 3000 lbs. Does anyone have a copy they can look up and verify. Don't want to assume the wrong capacity.

 

[oldestguy]

I don't have Joe's book, but I suspect you are misinterpreting something to be able to pick the bearing capacity based on a soil textural classification only.

 

[countyreviewer]

Is there a table I can look up that would better state the bearing capacity for SM soil class?

 

[fegenbush]

Table 4-8 (p. 274) of the book gives presumptive bearing capacities from indicated building codes. Depending on the code you reference in that table, Sand, compact and silty can give from 2,000 psf to 3,000 psf. When in doubt, assume low capacity.

 

[countyreviewer]

Thank you! The engineer had a 6 stack, 2x2x4 ecology block wall, and I was concerned that the soil bearing capacity was only 2000 and the blocks would be too heavy based on the spread. Even at 3000 lbs the factor of safety is low 1.5 if I assume each block weighs about 2700 lbs.

 

[msquared48]

Countyreviewer:

At 150 pcf for the concrete, 1' X 2' X 6 X 150pcf = 1800psf, well below the minimum of 2000 psf. There should be no bearing problem here, except if you are adding overturning pressures, much of which, could be dissipated with a wall batter of 1:6 or so.

Mike McCann
MMC Engineering