Soil weight on footings (yes or no)?
Soil weight on footings (yes or no)?
(OP)
I'm just wondering what other engineers do for footing design when the governing factor is the allowable bearing pressure. Do you include the weight of the soil that bears directly above the footing or do you ignore it? My company includes it and has included it for years but we did a survey of local engineers and not all of them do, and then they have smaller footings. We saw a part in the code that says the soil/footings is "permissible" to be used in calculating the soil bearing pressure. Does this mean we don't have to include it?
thanks for the feedback.
thanks for the feedback.






RE: Soil weight on footings (yes or no)?
Mike McCann
MMC Engineering
RE: Soil weight on footings (yes or no)?
"net" refers to the loads applied to the footing without regard to the soil weight.
there should be a discussion of this in your geotech textbook if you want to look into this further.
RE: Soil weight on footings (yes or no)?
Galambos, most of the residential homes don't include a soils report, the city gives us an allowable, but I'll check out how the city terms it, Thanks.
RE: Soil weight on footings (yes or no)?
Vanik Abedian,
Kartez Engineering, Inc.
RE: Soil weight on footings (yes or no)?
So you may have 4 feet of dirt over your footing, but the original grade was 3 feet above the footing. In that case you'd include 1 foot of surcharge soil in addition to your footing loads when using net allowable bearing pressures, but you'd neglect the 3 feet since that was "already there".
RE: Soil weight on footings (yes or no)?
RE: Soil weight on footings (yes or no)?
thanks
RE: Soil weight on footings (yes or no)?
RE: Soil weight on footings (yes or no)?
RE: Soil weight on footings (yes or no)?
The philosophy you describe is one that is used by many engineers throughout the world. As for most rules of thumb there are some exceptions to the rule.
1. I have actually encountered soils with a strong layer underlain by a weaker soil layer. It was so much weaker that I had some helical pile contractors refusing to tender in case they broke through to it.
2. The reason why the bearing pressure gets greater as you get deeper is because you are removing the soil over. So if you increase the pressures as indicated, you also have to include all loads from above including the weight of the soil.
RE: Soil weight on footings (yes or no)?