Bearing Pressure versus Contact Pressure

[NBRY1]

Is bearing pressure the same as contact pressure?
Are these terms/concepts separated by soil structure interaction?

For example, if I have a box that is 10ft x 10ft in plan, 1-ft height fill with water, bearing pressure exerted will be 62.4 psf.
But because the ground responds uniquely, the actual contact pressures may vary.....although commonly assumed to be uniform.

 

[MotorCity]

Yes. You can't have bearing without contact. The contact/bearing pressure could vary or be uniform depending on load and soil properties.

 

[NBRY1]

My point is that bearing pressure is load/area of application.......so is uniform because that is how it is defined q = P/A.
Contact pressure is certainly not uniform...usually.

So, I disagree, I say they are different in that regard, but the same in quantity.
Integral of contact pressure should be same in quantity as bearing pressure.
Is that correct perspective or am I overthinking?

 

[MotorCity]

Agree to disagree. Bearing pressure is not always uniform. Your equation above leaves out the Mc/I term of the basic bearing pressure equation. If the geotech gives me an allowable bearing pressure of 3000 psf and I have an eccentrically loaded foundation where the pressure varies from 2000 psf on one end, to 1000 psf at the other end, by your definition, I could not use the allowable bearing pressure to evaluate my foundation simply because its not uniform.

It comes down to semantics. Either term could be used interchangeably and the context would be understood.

 

[NBRY1]

According to your example, the bearing pressure would have triangular distribution, but that would not
be the same as the contact pressure, which is exactly my point.

 

[le99]

There is a difference between the terms, albeit small.

"Bear" means "press on", so bearing pressure refers to the pressure in between two surfaces while one is pressed onto/against the other. "Contact pressure" refers to the pressure on a surface that gets in contact/touch with another. In a sense, the former term strongly associates "pressure" with "deformation", and in the latter term, the association is weak.

 

[BigH]

Does rigid rigid foundation vs flexible foundation have any influence on contact pressures at the base of the foundation? Cohesive vs cohesionless? Just a thought . . .