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The results from 3 years of comprehensive field investigations on first-year ice ridges in the Arctic are presented in this paper. The scopes of these investigations were to fill existing knowledge gaps on ice ridges, gain understanding on ridge characteristics and study internal properties of ice. The ability of developing reliable simulations and load predictions for ridge-structure interactions is the final principal purpose, but beyond the scope of this paper. The presented data comprise ridge geometry, ice block dimensions from ridge sails, ice structure in the ridge and values on the ridge porosity and the degree of consolidation. The total ridge thickness conformed to other ridges studied in the same regions. The consolidated layer thickness was on average 2-3 times the level ice thickness. Minimum 33% and in average 90% of the ridge keel area was consolidated. The distribution of ice block sizes and block shapes within a ridge appears to be predictable. A new approach for deriving a possible ridging scenario and ridge age is presented. Different steps of the ridge building process were identified, which are in good agreement with earlier simulated ridging events. After formation of very thin lead ice between two floes deformation occurs through rafting and ridging until closure of the lead. Subsequently the adjacent level ice floe fractures proceeding ridge formation until ridging forces exceed driving forces. A time span of 10 days could be assessed for a possible ridge formation date, estimating the ridge age of the studied ridge located east of Edgeøya at 78° N to be 7 to 8 weeks.

The present paper deals with interaction between an ice sheet and fixed, conical structures. The ice sheet as well as the structure is discretizied by finite elements. The interaction between the ice sheet and the conical structure is simulated using a special contact algorithm which makes it possible to follow the gradually developing contact between the ice sheet and structure. As the configuration of the ice sheet changes during the interaction process, the buoyancy forces changes accordingly. This process is traced by introducing a continuous nonlinear foundation model to include the effects of buoyancy forces and specific weight of the ice. The mechanical behavior of ice is approximated using two different constitutive models. In the first material model the ice is treated as an isotropic, brittle material, while in the second model the ice is considered being a transversal isotropic, brittle material. When the state of stress at a material point in the ice reaches the failure surface, cracking or crushing is said to occur. After cracking or crushing, the post peak behavior of the ice is approximated as a rigid plastic material. The results obtained during the finite element simulations are compared with analytical methods for calculation of ice sheet forces on conical structures.

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