Mechanical Properties And Parameter Sensitivity Analysis Of Steel Pipe Pile Cofferdam In Complex Marine Environment

With the increasing of number of sea-crossing and river crossing bridges in our country,the construction of bridge foundation in the deep water is inevitable.In order to ensure the safe construction of pile cap,it is necessary to build temporary cofferdams to ensure that the construction can be carried out in a waterless environment,so as to facilitate the excavation of foundation pit and construction of structures.The application of steel tube pile cofferdam in the foundation construction of bridge in deep water is late in China.The steel tube pile cofferdam has the advantages of fast construction speed and large section stiffness,which can be applied to various complex strata and has broad application prospect.Most of the research on steel pipe pile cofferdam is the calculation and analysis,lack of research on the whole construction process of steel pipe pile cofferdam.In this paper,through the numerical simulation software Ansys Fluent and Ansys Workbench,typical working conditions in the actual project are selected to conduct full-scale analysis of single steel pipe pile working conditions,multiple steel pipe pile working conditions and overall cofferdam working conditions that may be encountered in the construction process of steel pipe pile cofferdam.The main contents are as follows:(1).Combined with the existing experimental and numerical simulation data,the correctness and rationality of a series of calculation parameters such as the grid size of the numerical model,the turbulence model and the decoupling mode of the governing equation are verified,and the numerical calculation method suitable for high Reynolds number three-dimensional two-phase flow around the flow is studied.(2).The flow around the single pile and fluid-structure coupling were studied under the condition of the first steel pipe pile being inserted into the steel pipe cofferdam,and the variation laws of water flow load and structural dynamic response of steel pipe piles with the different velocity,outer diameter and wall thickness are analyzed.(3).The three-dimensional flow around the cylinder and the structural dynamic response of multiple steel pipe piles inserted into the steel pipe cofferdam are studied,the stress characteristics,three-dimensional flow field and dynamic response of steel pipe piles under different arrangement modes and different number of pipes were analyzed in detail,and the effects of different number of pipe and arrangement modes on the stress,flow field and structural dynamic response of steel pipe piles are summarized.(4).Study the three-dimensional flow around the steel pipe pile cofferdam under the overall working condition and the dynamic response of each component of the cofferdam,and carry out parametric analysis on different steel pipe pile sizes,concrete thickness of the bottom sealing and elevation of enclosing purlin,so as to provide an optimization scheme for the design of steel pipe pile cofferdam.Through the research,the flow load variation law and structural response results of steel pipe piles with different flow rates,diameters and wall thicknesses were obtained under the condition of single steel pipe pile;The results of flow force load law,flow field change and structural response of multiple steel pipe piles under different arrangement and number conditions are obtained,and the solutions to reduce the load of steel pipe piles under different conditions are provided.The structural response results of each component of the steel pipe pile cofferdam during the cofferdam forming are obtained,and the parametric analysis is carried out,and the optimization scheme is provided for the practical design.The research results can provide reference for parameter selection and structure design of steel pipe pile cofferdam in the construction of bridge in deep water.