Relationship between cohesion and allowable bearing pressure
Relationship between cohesion and allowable bearing pressure
(OP)
I don't know if anyone out there is able to help.
I'm sitting some professional examinations here in the UK shortly, and have got hold of some typical past exam papers to attempt as part of my preparation.
I have noted in some of these papers that if the ground conditions comprise clays etc that values of effective cohesion are given.
Is anyone aware of an empirical method of converting this to an allowable bearing pressure I can use for preliminary deisgn?
If so, any references I can make use of for the exam would be much appreciated.
Regards VB
I'm sitting some professional examinations here in the UK shortly, and have got hold of some typical past exam papers to attempt as part of my preparation.
I have noted in some of these papers that if the ground conditions comprise clays etc that values of effective cohesion are given.
Is anyone aware of an empirical method of converting this to an allowable bearing pressure I can use for preliminary deisgn?
If so, any references I can make use of for the exam would be much appreciated.
Regards VB





RE: Relationship between cohesion and allowable bearing pressure
Terzaghi's method works just fine if you assume undrained conditions and phi=0 degrees.
Usually, the coefficients of Nc, Nq and Ng are those developed by Meyerhof and Vesic, or some combination thereof.
When undrained conditions are assumed, Nq=1, Nc=5.14, and Ng=0.
q(all) = (c*Nc + q*Nq) / FS
where the second "q" = gamma'*Df
For shallow footings, FS is usually taken as 3.0.
You may wish to add a soil mechanics text to your prep materials, as this method is about as basic as it gets. (Don't ask me about structural engineering - I'd need quite some time to review and refresh)
Jeff
RE: Relationship between cohesion and allowable bearing pressure
I just wanted to clarify - for the second 'q' = gamma * Df
I assume gamma is the density of founding material, and Df = depth of foundation?
Regards
VB
RE: Relationship between cohesion and allowable bearing pressure
you should use gamma' - the effective unit weight (not strictly the same thing as density) of the soil above the foundation bearing depth.
Jeff
RE: Relationship between cohesion and allowable bearing pressure
Regards
VB
RE: Relationship between cohesion and allowable bearing pressure
RE: Relationship between cohesion and allowable bearing pressure
f-d
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