Some Tasks of Increasing and Identifying the Reserves of the Bearing Capacity of Anchor Fastenings of Offshore Fixed Platforms

With the development of great depths of the sea and the need to drill deep wells from stationary platforms, the issue of using an anchor fastening design with a large bearing capacity became acute, and for this purpose, a combined type design was proposed. The design feature is that a metal pipe driven into the upper layer of weak soil of the sea bottom, through which a well is drilled to the required depth, forms an ordinary bored pile in the lower part, followed by filling the entire internal cavity with cement mortar to the level of the platform, inside which the platform is installed tubular metal anchor. The purpose of this design was to reduce the length of the anchor fastening in the ground with the same bearing capacity due to additional pouring with cement mortar. At the same time, to assess the bearing capacity of such a structure, a calculation model is used, which consists of the fact that the cement slurry, before hardening, produces lateral pressure on the walls of the wells, similar to hydraulic pressure, and the reaction from the soil is taken equal to this pressure, and it remains unchanged in magnitude even when the cement slurry hardens. As for the bearing capacity of the butt, the solution of the problem obtained for a round stamp pressed into an elastic–plastic body is used for it. Taking into account also the bearing capacity of the clogged part of the structure, calculation formulas were obtained to determine the bearing capacity of the combined anchor fastening. According to the regulations on environmental protection, drilling works are carried out with seawater and a solution made from natural clay, the resulting slurry does not contain harmful toxic substances and it is allowed to be thrown to the bottom of the sea as it does not pollute the environment. Pouring this solution to the bottom of the sea does not violate the requirements of the legislation on protecting the economic importance of water bodies and the natural local conditions inhabited by living organisms from an ecological point of view.