EXPERIMENTAL JUSTIFICATION OF METHODS FOR MITIGATION OF ICE ACTIONS ON OFFSHORE STRUCTURES AND FOR ICE LOADS CALCULATION

When designing ice-resistant oil-and-gas production platforms, special attention shall be paid to selection of ice belt shape and embodiment to promote ice loads decrease. Such selection largely depends on maximum thickness values of the level ice acting on the platform. The main goal of the work consists in searching for new ice belt shapes and structural elements that ensure ice loads reduction and decrease of offshore structures material consumption, experimental evaluation of their effectiveness and development of loads calculation method. For this purpose, main specific features of ice failure near offshore structures were analyzed for various ice thicknesses, an attempt to classify ice-breaking devices was made, 3D experimental studies of ice belt small-scale models under thick and thin ice actions were performed. Some effective innovative solutions on thin ice failure are known that consist in installation of pyramidal ice-breaking extensions on the ice belt. In the course of their contacts with the ice, in the area of their ridges (intersection of pyramid sides) stress concentration is observed that causes quick development of ice plastic flow in these areas (at very low loads on the structure), ice plastic deformation constraint in the ice concentration areas and initiation of radial and then circumferential cracks that results in separation of ice fragments (in the shape of sectors) from the ice field. Such solutions are helpful when breaking the thick ice as well; however, with ice thickness growth their effectiveness decreases. Other effective solutions are proposed in the work that incorporate elements arranged near the middle of the ice plate height that stratify the thick ice. It is useful to combine such elements with ice-breaking pyramids adjoined to them that promote forming radial and circumferential cracks in the ice. The work results include recommendations on designing ice belts of steel oil-and-gas production platforms operating under actions of ice of various thickness, as well as the method for calculating ice loads on legs of platforms with new ice-breaking extensions. The results of the work are aimed to creation of profitable robust and reliable oil-and-gas production platforms for the Arctic.