Vertical-faced structures will experience large horizontal forces, while inclined faces will tend to reduce
the total force acting on the structure. Static ice forces result from thermal 6xpansion and contraction of
relatively stationary ice sheets. Fractured ice forces arise from broken pack ice driven against a structure.
Uplift and drawdown forces are associated with the adhesion of floating ice sheets to structures.
Water level fluctuations caused by seiches, tides, or reservoir operation can result in significant
damage to pile-supported structures. Water level recession can cause considerable downward loadings
that force the piles deeper into the bottom. Conversely, water surface rises will pull the piles upward. As
this occurs, the soil will collapse beneath the pile tips and will prevent return to their original positions.
A series of such actions can jack the piles completely out of the bottom.
Possible preventative measures include air bubbler systems and pile sleeves, but these must be
evaluated on an individual case basis. Relatively comprehensive summaries of current methods for
evaluating ice forces on structures are given in Neill (1976), Wortley (1978) and the U. S. Army Corps of
Engineers (1980b).
Vandalism and Theft. The final factor is the susceptibility of the structure to vandalism. If this
may be a problem, materials should be selected which cannot easily be cut, carried away, dismantled or
otherwise damaged. For instance, sand-filled fabric bags are easily slashed by knives, small concrete
blocks can be stolen, and wire mesh baskets can be opened with wire cutters and the contents scattered.
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