Experimental study of tsunami-type waves impact on soil near foundation of offshore gravitational-type platforms

摘要

The need to study the problem of seabed local scour near offshore platforms has arisen in Russian Federation in connection with the activation of oil and gas production from fields located in coastal areas of seas (in accordance with the Energy Strategy for the period up to 2030, approved by the Government of the Russian Federation on November 13, 2009, No1715-p). Operation of offshore platforms is characterized by a number of features: shallow water areas; severe storm conditions; large transverse dimensions of structures that cause waves diffraction; the variety of used structure forms; the way of platform mounting on the seabed. During platform operation in the shallow waters, its basement soil is under an intense impact of sea waves, currents, as well as jets from engine of coming and berthing ships. The structure disturbs the natural wave flow. Near the platform, flow velocity increases, there are vortexes breakaway from platform corner edges. Scour holes appear and progress near platform foundation. Their location and measure depend on the parameters of external impacts, on the water depth, on the shape and dimensions of the foundation block. Scour holes reduce the overall stability of the structure. Their effect on the structure operation depends on the location and the type of supports (gravity-based or pile). With the scouring beginning, its may progress and lead to soil base washing-out from under the structure foundation. It can cause harmful conditions for normal operation of the structure.