15 August 2002
5-220.127.116.11.1 Weight. In computing the weight of this block, assume its plan
dimensions to extend beyond the outer rows of piles by a distance of one-half the
typical pile spacing.
5-18.104.22.168.2 Depth. For the depth of block, assume the block bottom is above the pile
tips by a distance of one-half the typical pile spacing. Where spacings are different in
each direction, use the larger of the spacings.
Weight of Water. In computing pressures, use 1025 kg/m3 (64 lb/ft3) for
seawater and 1002 kg/m3 (62.5 lb/ft3) for fresh water.
. Make all buoyancy computations for three
water levels, as follows:
Extreme high water. To check safety against uplift with the maximum
(15 degrees) earth wedge mobilized.
Mean high water. To check safety against uplift with the minimum earth
block and friction mobilized. Refer to section. 5-2 for dead loads and section 5-4 for
Extreme low water. With a ship in dock to determine maximum
downward load on foundation soil or piles.
Variations. Acting against a dock structure, the resultant outside earth
pressure will vary considerably according to pressure and weight conditions inside the
dock. Resultant earth pressures will be different when a dock is full of water, when a
dock is dry but contains a vessel, and when a dock is empty. See DM-7.02
Foundations and Earth Structures for determination of earth pressures.
Water or Ship in Dock. Active pressure is to be used because the
rotation of the wall with respect to the floor is negligible. Do not use surcharge for
computing pressure on drydock walls except where railroad rails on ballast are near the
Dock Empty. Assume partial passive pressure to be operative where
there is structural continuity at the juncture between sidewalls and floor because, with
the dock empty, sidewalls of full hydrostatic docks have a tendency to rotate outward
a uniform increase in resistance to occur throughout the sidewall height, starting from
zero value at the top to an ascertained maximum bottom value. The rate of increase is
based on the condition that the total internal work of the bending stresses throughout
the dock cross section has a minimum value.