The Analysis Of Driven Riser Capacity Changed With Time

With the development of offshore oil, the technical requirement of the offshore platform becomes higher. Before the implement of offshore platform, a jumbo size steel pipe must be driven into clay first. This kind of steel pipe called riser, used for insulating sea water so as to form the canal of drill fluid and bearing the load of platform and wellhead equipment. In a word, the bearing capacity of riser badly affects the stability of the offshore platform. Many projects have shown that the bearing capacity of riser was not invariable after driven, but increasing with time. For the above, this paper will analysis the initial excess pore water pressure caused by riser driven into saturated clay, the dissipation of excess pore water pressure and consolidation of soil, so as to research the rule of the bearing capacity of riser with time.Firstly, the initial excess pore water pressure due to riser driven into saturated clay is researched. Based on the documents we have, the area of soil affected by the riser driven into saturated clay is given. Over analyzing the data of the initial excess pore pressure from the foreign driven pile experiments, the distribution of the initial excess pore water pressure due to riser driving is analyzed.Secondly, the dissipation of excess pore water pressure and consolidation of soil is researched. Based on the Biot consolidation theory, the engineering software FLAC is used to simulate the scatter process of the excess pore water pressure.Finally, the bearing capacity of riser with time is researched. Using the engineering software FLAC, the bearing capacity of riser is analyzed. Over setting flow time, the bearing capacity of riser can be confirmed at different time, from which we can get the rule of riser capacity changed with time. Moreover, the factors which affect the riser capacity with time are analyzed too.