Study On Bearing Characteristics And The Influencing Factors Of Bearing Capacity Of Steel Pipe Piles Under Inclined Load

With the rapid development of subsea engineering,the development of offshore energy has advanced from the shallow sea to the deep sea.Floating structure is a common structural form in deep sea engineering.Generally,suction pipe pile foundation is used as anchor foundation.Researches on suction piles by domestic and foreign scholars are mostly carried out by small-scale model tests and numerical simulations.The study on the bearing characteristics of steel pipe piles under inclined pull load is still in the initial stage.In order to make the research results more in line with the actual conditions of the engineering,this thesis relies on Shanxi Province's “Hundred People Project”(deep sea structure and foundation,project number: 800101-02030017),using large-scale steel pipe pile models,based on array displacement meter testing technology,the pile was subjected to a laboratory test of the load-bearing characteristics under inclined pull load.Combined with the numerical simulation analysis,the failure characteristics under different working conditions were explored.The effects of different aspect ratios,different loading angles and position of loading on the bearing behavior of steel pipe piles were studied systematically.In the scope of this study,the following main conclusions have been obtained:(1)Through the indoor test of steel pipe piles model under 5 working conditions,this thesis obtained that,under the condition of the same aspect ratio the ability of steel pipe pile to resist inclined pull load decreases as the load angle increases,while under the condition of the same loading angle,the ability of steel pipe piles to resist inclined pull load increases as the aspect ratio increases.According to the damage characteristics,the soil around the steel pipe piles produced different degrees failure under five conditions.The wedge-shaped body was formed on the passive side of the pile and raised at a certain height.There were several cracks on the wedge body,and the subsidence and cracks appeared on the active side of the pile.(2)The Shape Acceleration Array displacement meter technique was applied in this experiment,and the displacement state of the pile body under different loads was monitored in real time,indicating that the displacement of the pile body is composed of translation and rotation under inclined pull load.Under different loading conditions and pile parameters,the ratios of translation and rotation displacements are different.(3)The finite element analysis shows that,the effect of the position of the load on the ultimate bearing capacity is related to the angle of the load.When the load angle is greater or equal to 30°,the effect of the position of the load on the ultimate bearing capacity of the steel pipe pile under the inclined pull load is not affected much.When the loading angle is less than or equal to 15°,the position of the load has a great influence on the ultimate bearing capacity of the steel-pipe pile under the action of diagonal load.When the diagonal load acts at 0.8L from the top of the pile,the ultimate bearing capacity of the steel pipe pile achieves the maximum value.The ultimate bearing capacity of steel pipe piles under inclined pull load increases with the increase of the aspect ratio.The ultimate bearing capacity of steel pipe piles under oblique load decreases with the increase of loading angle.This change is significant when the loading angle is less than or equal to 30°.When the loading angle is greater than 30°,this change becomes gentle.To sum up,when steel pipe piles are used as anchor foundations in the engineering,it is recommended that the mooring position be set at the lower part of the pile as much as possible,and a smaller loading angle should be adopted.In addition,when the conditions are favorable,steel pipe pile with a large aspect ratio are preferred.