thick and unsatisfactory overburden material to reach suitable bearing
material. The primary difference between caissons and pile foundations is
the construction procedures used to penetrate soft or loose overburden
material. Piles are usually driven whereas caissons are usually excavated by
drilling into the ground. In addition, as opposed to driven piles, caissons
may also have their lower ends enlarged by belling if the bearing strata is
sufficiently stable to permit this operation.
4.
FOUNDATION TYPE SELECTION. Consider the following factors in making the
final foundation type selection:
a.
Design the hyperbaric facility to compensate for soils which
could Allow excessive differential settlement after the chamber is completed,
by:
(1) Designing the chamber, its components and supporting
structure, for the estimated differential movements.
(2) Supporting all sensitive components on a common foundation
such as a raft or mat foundation designed to provide adequate stiffness.
(3) Using an extended foundation such as piles or caissons to
reach a soil-bearing strata which is sufficiently stable.
b.
If hydrostatic uplift due to ground water pressures must be
resisted, the facility must have adequate dead weight to resist the uplift or
it must be anchored to an extended foundation which can mobilize sufficient
soil below the facility to resist the uplift. In either case, the dead
weight plus anchorage, If any, should exceed the uplift by an acceptable
margin.
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