Monolithic Pad Footing Bearing Capacity

[1SEngineer]

I'd like to calculate the maximum capacity of a monolithic pad footing including the sloped sides and any acceptable portion of the slab on grade.

Specs:
4'x4'x16" deep
sloped sides are 45 degrees
4" slab on grade

I typically wouldn't consider using the sloped sides or the slab on grade, but I was curious to know how much a footing such as this can actually support. I normally would only use the 4'x4' area of 16 sq.ft.

I believe that the Hansen method is appropriate for this calculation.?

Thanks

 

[1SEngineer]

I neglected to mention soil properties.

c = 0
phi = 32 degrees
weight = 115 psf

Typical soil allowable bearing cpacity = 2500 psf

 

[csd72]

Maybe it is in here:

http://wirereinforcementinstitute.org/pages/pubs/pdf/TF 700-R-03.pdf

csd

 

[civilperson]

Is this a soil problem or a footing problem? The soil allowable bearing capacity is usually governed by settlement concerns rather than a shear failure in the soil. The height of the backfill above the bottom of the footing effects the shear failure stress and thus the slab on grade would contribute to shear resistance. Normal practice is to use the design soil level as level with the bottom of the footing for conservative calculations. The strength of the slab in flexure when the footing reacts downward is the limiting case of trying to use the slab as a foundation element.

 

[BigH]

civilperson - I think it is a student problem - but hope I am wrong.

 

[UcfSE]

I don't think you can reliably count on the contribution of the sloped portion and the slab. Both would have to be analyzed and reinforced. This would be difficult to enforce in the field since it is an unusual detail.

 

[1SEngineer]

This is a hypothetical problem.

I am curious to know what the soil bearing capacity would be.

I know it isn't common practice to use the sloped sides or the slab...but what if one wanted to?