Bearing capacity of soil below gravity wall

[jeabramian]

Dear All,

I need to verify an old gravity wall. Let's say the left side is dredged just above the toe and the right side is filled with clay. Foundation layer is sand N=35. Watertable is about in the middle of the height on the right side, and the river is taken to be somewhat below the watertable.

There is a prestressed anchor on the right side (A) 30° inclined downwards. On top there are moving cranes on rails (V) and some horizontal loads (H).

When there are no cranes on top, or there are small loads, due to the anchor, the soil pressures at the bottom are higher on the heel side than on the toe.

And in some cases max pressures are higher than the bearing capacity. The worst case is when there are no loads on top, I guess it is because the loads tend to lower the eccentricity. This is very counterintuitive: the lower the loads, the lower the FOS.

I'm calculating the soil pressures including the anchor prestressed load.
I'm calculating the bearing capacity with the generalized Terzhaghi formula where C=0, fi = 30°.

I checked in Braja Das book and says that q= Df.Gamma_sand, with Df being the soil depth at the dredged side (almost zero) and gamma = gamma submerged.
Is this correct?

Am I missing something?

Many thanks in advance.

Jorge

 

[MotorCity]

If you are calculating the bearing capacity based on the assumed values of certain parameters, you might as well skip all of those calculations and just assume a conservative bearing capacity.