Calculated and measured values of stresses and ice forces under ice compacting leading to the ridging of the ice floes are presented in this paper. The calculated stresses were obtained using the knowledge of the ice strength characteristics. For the ice thickness exceeding 1 m, the ice forces can reach the order of several MN. 1m-1 Some evaluations of the ice forces obtained by calculations based on the mathematical modeling of the ice compacting processes are also presented. The critical values of the calculated stresses are close to the measured stresses, when dimensions of compacting zones are of the order of hundreds of kilometers.
Of all the dynamic processes in the sea ice cover, ice compacting is most dangerous for ships and hydrotechnical structures. Ice compression usually reveals itself in ice fracture of different types and ice ridging, and it is the last stage of the ice cover compacting. The ice-floe drift irregularities due to non-uniformity of the external forces, and the influence of the sea coast are the direct cause of the appearance of stresses in the sea ice. The spatial non uniformity of the ice compacting affects, in its turn, the adverse influence on the drift velocity; it is known that in the compacting sea ice cover, the stresses can be transferred for a substantial distance of the order of hundreds of kilometers. A normative document (Bushuev et al., "Scale of the ice compacting," 1981) takes into account the dynamic state of the ice cover, in which the gradations of 0, 1, 2, 3 numbers are determined on the grounds of the qualitative visual indications. Results of the direct stress measurements in the ice cover were presented earlier, by Sackinger and Nelson (1979), and Comfort and Ritch (1990).