characteristics of the soils, and complex geologic structure of the foundation. The main goals of calculating the coaction of the IFP and its foundation during construction and operation are to provide stability of the platform and strength of its foundation; to satisfy the criteria with respect to settlements, horizontal displacements, and tilting of the platform; to prevent impermissible erosion of the foundation soil; to provide conditions for erecting the platform on the ground and joining it to the foundation. In accordance with [5, 6], the calculation is made with respect to two groups of limit states to ensure technical safety and reliability of the IFP. The first group includes calculations of the strength of structural members of the platform and bearing capacity of the foundation soil. In particular, the bearing capacity of the foundation as a whole under the effect of the most dangerous load combinations is determined, the resistance of the foundation to crushing of projecting parts in the bottom of the platform when installing it in place is calculated, the resistance of the soil to shearing of the platform along its bottom under the usual and unusual load combinations is determined, and the local resistance of the foundation soil to erosion and other local actions when installing and operating the platform is estimatedl The second group includes calculations of IFPs, including estimates of short- and long-term settlements and tilts, displacements under the effect of long-acting and multiple loads, and the dynamic reaction of the platform--foundation system to wave and ice effects. It should be taken into account that during construction and operation of IFPs the characteristics of the foundation soils change under the effect of a number of factors (loads, time, temperature, etc.), and the factors themselves also undergo changes. In connection with this, the obtainment of initial data for designing IFPs is extremely important and requires reflection in the standards. Initial Data. The most important problems that did not find due elucidation in [6] but that are the basic ones for obtaining correct calculation results are problems of obtaining objective initial data: assessment of the engineering-geologic conditions of the site of installing the platform, determination of the design characteristics of the engineering-geologic elements of the foundation and its design schematization, determination of the magnitudes and combinations of loads and actions. Experience in calculated substantiation of the stability of platforms and evaluation of the stress--strain state of their foundations indicates the fundamental significance of the indicated problems, which proved to be the most acute and determined the design of the structure--foundation system.