Uplift Pressure
and Buoyancy
Water pressure exerts an uplift force on the underside of a structure
whose base sits below the water table. If the uplift force is greater
than the weight of the structure, the structure will float.
In the drawing below,
W = weight of structure
A = total anchor force
h
=
height of water table above base of structure
.
w
= density of water
uh
w
==
.
uplift water pressure
Uplift pressure increases with pore-water pressure. Monitoring
pore-water pressure during the design stage can help in assessing the
need for anchors to counter buoyancy.
Seepage under a concrete gravity dam can create uplift pressures
that are destabilizing. Monitoring pore-water pressures under the
dam provides input to stability calculations and may indicate the po-
tential for failure and the need for remedial action.
Basic Soil Mechanics
BS-up1.cdr
W
u
Gr ou n d An c h or s
A
h
G ro u n d W at e r L e v el
Rembco Geotechnical Contractors specializes in
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Rembco techniques apply when adding new structures: especially
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