All of the determinations were made with samples of ice taken from shore fast ice which had not 

 undergone any movements during the winter. 



Table 64 gives the results of the limit of plasticity of sea ice in flexure, conducted by 

 Arnold- Aliabev. 



TABLE 64. LIMIT OF PLASTICITY OF SEA ICE EST FLEXURE IN KG/CM^ 



Besides the table, Arnold- Aliabev presented the following formula 



W = 4. 7 - 0.96t - 0.31t^, 

 where W-, is the limit of plasticity of ice in kg/cm . 



(1) 



As Arnold-Aliabev indicates, if the deviation due to ice salinity is removed, it is possible to 

 obtain the following formula: 



W -W = 0.155,. - 0.34, 



1 '■ 



where W-^^ is the amount computed according to formula (1), 5 • is the salinity of the ice. 



(2) 



In the theory of resistance of materials it is considered that the effect of local faults- cracks, 

 faults and interlayers of various sorts of sufficiently plastic substance, is reflected in a decrease 

 of strength as well as a decrease in the cross section of the samples being tested. The same 

 allowance can be applied to the salt cells and the air pores included in sea ice. 



Arnold-Aliabev investigated 28 samples of ice from the Gulf of Finland for breakage in which 

 the air content had been determined previously. The results of these tests are presented in 

 figure 62 from which it can be seen that with a decrease in the air content, the limit of plasticity 

 of ice rises considerably, varying from 10 to 25 kg/cm^ at air temperatures from -5° to -7°. 



According to the observations by the above author, the ice of the Barents Sea yielded a limit 

 of plasticity during breaking of only 8 to 12 kg/cm^ with a considerably greater air content (and a 

 higher salinity) at a temperature of -5°. 



Further, Tsurikov, assuming that the bubble spaces are either spherical (which, in his 

 opinion, occurs in ice at low temperatures and porosity) or cylindrical forms (during the summer), 

 derived a formula according to which it is possible to compute the relative decrease in the limit of 

 plasticity of ice during breakage and compression in comparison with the same amounts for old ice. 

 A comparison of the theoretical computations with the actual measurements yielded quite good results. 



190 



