Investigation of jetting system of the spudcan to ease extraction in clayey soils

An offshore wind turbine in shallow water is installed by a self-elevated mobile unit that is usually referred to as a jack-up barge or jack-up vessel. The jack-up vessel consists of a buoyant platform together with independent legs that can position the vessel above the water, thereby reducing external loadings for a safe operation condition. The retrieval process for the jack-up legs can be very difficult due to the high extraction resistance caused by soft soil. In soft clay, high suction force can develop around the spudcan attached at the end of the jack-up legs. Therefore, a jetting system is required to break the suction in order to pull out the legs. It is important to design the jetting system with an optimized piping arrangement to allow the easy operation. Various factors must be considered in the design of the jetting piping system since the level of embedment, type of soil, and pipe sizes and locations can affect the performance of the system. In this paper, we present the characteristics of west coast geological features by subsea geological survey and the design of jetting system that was analyzed using pipe flow analysis program.