A method to define the characteristics of the design storm is proposed to account for cycle-after-cycle loading of soil foundations of gravity submersible ice-resistance platforms. The method is based on the Slepian's model used in the theory of normal distribution of stationary random variables. The definition of the basic characteristics of the design storm is illustrated by practical examples for the conditions of Piltun-Astokhskoye and Lunskoye deposits.


The engineering maintenance of various stages of arrangement and development of offshore oil-gas deposits is accompanied by construction of stationary submersible platforms. The main part of the perspective oil- and gas-oriented offshore zones of Russia is located in the freezing seas with heavy ice regime, severe natural-climatic conditions and weakly developed coastal infrastructure (in the Arctic and Far East seas). Further design developments, perfection of existing calculation methods, experimental verification of design proposals are required. In defining the bearing capacity of soil foundations of offshore ice resistance submersible platforms it is necessary to take into account cyclic character of the applied external natural loads (for example, wave, ice, seismic ones). Under action on the platforms of loads from waves in non-cohesive soils of the foundation during the storm the growth of porous pressure in liquid is observed that leads to reduction of strength characteristics of the soil. The value of this reduction depends on the following factors: characteristics of the design storm - its general duration, rate of growth and decrease of waves height, duration of the sea state, when the statistical characteristics of the waves can be considered stationary; the size of the footing of the base substructure; type of soil of the foundation; draining ability of the soil boundaries; the relationship of the amplitudes of cyclic loads to the values of the dead loads, etc.

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