In a still more rough approximation, it can be considered that for the salty ice of the white 

 arctic and far eastern seas, 



/2s = 1 .6 ho; 



for the slightly saline ice of the Gulf of Finland, the Sea of Azov and the northern part of the 

 Caspian Sea 



hs = \.3 ho. 

 Now combining the approximate formulas we obtain 



/J,s = (l+0.1S,)10]/^^, 



= ^' 1 — ^ 1 



^" 100 10 (I + 0.1S;)2 ' 



(12) 



(13) 



(14) 

 (15) 



where h-j.^ is the thickness of the ice at temperature t and salinity 5 ., supporting a load p. p , is 

 the wei^t of the concentrated load in tons which can be supported by the ice, at temperature t and 

 with salinity 6"^, h is the thickness in cm of fresh ice, whose temperature was -9°, 5" . is the 

 salinity of the ice, and t is the temperature of the ice. 



K the temperature of the ice is -15°, the salinity 5 o/oo and the thickness 50 cm, accordlr^ 

 to formula (15) we find that the load is about 21 m. 



LITERATURE: 76, 91. 



Section 79. Flexure of Ice Under Load 



As has already been noted, ice has plasticity under comparatively small loads, bends and 

 changes its form, but does not break. 



One can walk on fresh Ice 4 to 5 cm thick and sea ice 5 to 6 cm thick at which time the surface 

 of the ice is springy underfoot. An impression is created that one is walking over tightly stretched 

 hide. A blow on such a surface, if the ice is not broken by it, causes the formation of concentric 

 waves on the surface of young ice. * 



The flexure of ice can also be observed during tidal fluctuations of the sea level along the 

 shores, and especially near cliffs rising out of the water. The phenomenon is expressed in the 

 form of a concave surface during outgoing tide and a convex surface during incoming tide and the 

 ice far from shore, bending in conformity with the incoming tidal wave, does not crack. 



The flexure of ice is most clearly shown under the weight of loads placed upon it. Figure 63 

 shows (according to Bernstein) the sagging of ice under a railroad car on tracks laid on river ice. 



*It has often been observed that when a sea wave enters a gulf or bay covered with thin, young 

 ice, it is propagated in the form of a swell for some distance into the bay and ice 10 cm thick bends 

 in the form of the sweU. 



193 



