Design And Research Of Integrative Suction Foundation For Tension Leg Platform

Tension leg platform (TLP) is one of the most popular structures in developing deep sea. Its foundation includes two forms, pile foundation and bucket foundation. Compared to pile foundation, bucket foundation is more applicable to TLP in poor geological conditions of deep seabed, because it's particularly appropriate for soft ground of deep sea. However, the current water depth is only from 330 to 350 meters when bucket foundation is applied to TLP, which can't meet the requirement of development of deep sea.To solve this problem, after carefully researching bucket foundation, a new foundation form called integrative suction foundation is designed in this paper, which can be applied to water depth of 1,000 meters for tension leg platform. In this design, the most important part is the compressive water storage compartment, which completely changes the traditional method of using diving pump to generate suction, and utilizes the high pressure to press water into the compartment to generate suction. Then, the bucket foundation will be pressed into soil at preconcerted depth.Based on the environmental conditions of South China Sea and characteristic of high pressure in deep water, this paper chooses one best precept of foundation structure and carries through detailed design for it. First, according to the design, build finite element model, carry on static analysis of the structure, and certificate results by criterions of CCS. Then, calculate overall stability for the foundation, including sinking resistance, breakout force and vertical bearing force, the result of which shows the structure meets the requirement of strength and stability, as well as the performance requirement, and also shows it can be properly used in clay and sand.Integrative suction foundation changes the traditional method of using diving pump to generate suction, which greatly increases the application water depth of suction foundations for tension leg platforms. Moreover, four buckets penetrate at the same time, which not only remarkably shorten the construction period at sea, and significantly reduce the construction cost and operational risk, but also keep the four tensionlegs being parallel. Compared to previous foundation forms, it has obvious advantages and it is feasible in deep water environment with high pressure proved by calculation results. To sum up, integrative suction foundation is a new form of TLP foundations; it has great importance on the development of deep-sea resources of China, particularly for the oil and gas field of South China Sea.