The amount of expansion of fresh water in cooling from 12.6° C (39° F) to 0° 

 C (32° F) is 0.0132 percent; in changing from water at 0°C (32 F) to ice at 0° 

 C, the amount of expansion is approximately 9.05 percent, or 685 times as 

 great. A change of ice structure to denser form takes place when with a 

 temperature lower than -22° C (-8°F), it is subjected to pressures greater than 

 about 200 kilonewtons per square meter (30,000 pounds per square inch). 

 Excessive pressure, with temperatures above -22° C, causes the ice to melt. 

 With the temperature below -22° C, the change to a denser form at high pressure 

 results in shrinkage which relieves pressure. Thus, the probable maximum 

 pressure that can be produced by water freezing in an enclosed space is 

 approximately 200 kilonewtons per square meter (30,000 pounds per square 

 inch) . 



Designs for dams include allowances for ice pressures of as much as 

 657,000 to 730,000 newtons per meter (45,000 to 50,000 pounds per linear 

 foot). The crushing strength of ice is about 2,750 kilonewtons per square 

 meter (400 pounds per square inch). Thrust per meter for various thicknesses 

 of ice is about 43,000 kilograms for 0.5 meter, 86,000 kilograms for 1.0 

 meter, etc. Structures subject to blows from floating ice should be capable 

 of resisting 97,650 to 120,000 kilograms per square meter (10 to 12 tons per 

 square foot, or 139 to 167 pounds per square inch) on the area exposed to the 

 greatest thickness of floating ice. 



Ice also expands when warmed from temperatures below freezing to a 

 temperature of 0°C without melting. Assuming a lake surface free of snow with 

 an average coefficient of expansion of ice between -7 ° C (20° F) and 0°C 

 equaling 0.0000512 m/m- °C , the total expansion of a sheet of ice a kilometer 

 long for a rise in temperature of 10° C (50° F) would be 0.5 meter. 



Normally, shore structures are subject to wave forces comparable in 

 magnitude to the maximum probable pressure that might be developed by an ice 

 sheet. As the maximum wave forces and ice thrust cannot occur at the same 

 time, usually no special allowance is made for overturning stability to resist 

 ice thrust. However, where heavy ice, either in the form of a solid ice sheet 

 or floating ice fields may occur, adequate precautions must be taken to ensure 

 that the structure is secure against sliding on its base. Ice breakers may be 

 required in sheltered water where wave action does not require a heavy 

 structure. 



Floating ice fields when driven by a strong wind or current may exert 

 great pressure on structures by piling up on them in large ice packs. This 

 condition must be given special attention in the design of small isolated 

 structures. However, because of the flexibility of an ice field, pressures 

 probably are not as great as those of a solid ice sheet in a confined area. 



Ice formations at times cause considerable damage on shores in local 

 areas, but their net effects are largely beneficial. Spray from winds and 

 waves freezes on the banks and structures along the shore, covering them with 

 a protective layer of ice. Ice piled on shore by wind and wave action does 

 not, in general, cause serious damage to beaches, bulkheads, or protective 

 riprap, but provides additional protection against severe winter waves. Ice 

 often affects impoundment of littoral drift. Updrift source material is less 

 erodible when frozen, and windrowed ice is a barrier to shoreward-moving wave 

 energy; therefore, the quantity of material reaching an impounding structure 



7-254 



