Research On Behavior Of Large Diameter Steel Pipe Pile Under Lateral Load

Single pile foundation is widely used in construction industry for its characteristics of simple structure, mature design method, convenient construction and tech- economic advantages. In recent years, with the development of ocean engineering and the building of sea-crossing bridge, especially the rapid emergence of wind energy, pile foundation takes on the tendency of increase in both diameter and penetration, and the emphasis in pile foundation design shifted to effective control of the pile horizontal displacement other than the control of bearing capacity. Considering the development of single pile foundation's type, the method of deciding the horizontal bearing capacity is mainly based on the research results of small diameter or medium-diameter steel piles or reinforced concrete piles, Countries have no specific industry standards relevant for the design of large diameter piles.Therefore, the study of the horizontal bearing capacity of large-diameter pile has important theoretical significance and practical significance. In this paper, the study of the horizontal bearing capacity of large-diameter pile will be the study of the core and carry out research in the following aspects.By reading the literature, analyzing and summarizing research results and the development and application of evolution of the horizontal bearing piles.and also summarizing the problems and future direction of development. Describe the theoretical basis and scope of the m-method, p—y method, limit ground reaction force method, composite stiffness and two-parameter method which can be used to calculate the horizontal bearing capacity of piles,and the corresponding computer program was written which can be used to calibrated with numerical simulation results . And analyze how the ratio of pile diameter to length ratio affect the horizontal bearing capacity. Raise the concept of shell damage effects should be considered when we calculate the horizontal deflection of large-diameter pile. Theoretical methods will be used for practical engineering analysis of pile bearing capacity of horizontally. Focus on the pile diameter to length ratio change on the horizontal impact load model. With one offshore wind power project in Fujian,the author analyzed the horizontal deflection of large-diameter pile using different theoretical approaches. After comparing the calculation results,the author put forward a different theoretical methods used in large diameter horizontal bearing capacity of pile applicability.Traditional methods of calculating and analyzing of large diameter piles can not meet the design and checking. The destruction model of large diameter steel pipe pile should take into account the local buckling failure of the shell. There should also be considered the initial imperfection buckling and post buckling failure . When the horizontal load is smaller, Small-diameter piles (3m or less) can be calculated using m-method with a more accurate method, Large-diameter piles (3m or more) with p-y curve method more appropriately reflects the shaping of soil pile damage and results are in good agreement with the engineering practice. Large-diameter steel pipe piles under horizontal loads will produce local buckling and trends and buckling failure is extremely complex. In this paper, the author proposed the formula to determine the local buckling of the steel pipe pile. In the design, in addition to the horizontal capacity required to meet the requirements of the pile, still need to check the stability of its shell. For different diameter steel pipe piles ,the author made a finite element numerical simulation. And used beam elements and shell elements, respectively, for six groups of simulation analysis of steel pipe pile. The results showed that analysis with beam elements can be more consistent with the calculated results when the pile diameter is smaller .and when the diameter is larger, analysis with shell elements can be more accurate. This study has some theoretical content of value and practical significance of engineering.