| Summary: | 碩士 === 國立中興大學 === 水土保持學系所 === 104 === This study use the actual measurement data of the wind farm at Chang-Hua coast of western Taiwan, then under the simulation by three-dimensional (3-D) finite element program Plaxis 3-D. This study investigates the dynamics reactions and mechanical behaviors of pile foundation installed on the seabed of wind farm near Chan-Hua coast of western Taiwan for the supporting structure of offshore wind turbine.
Firstly, using the boring logs, SPT-N values, and laboratory tests of undisturbed samples from the wind farm, one can estimate the required material model paramters of soil strata for numerical model. In addition, consulting the commonly used interanational design criteria and recent case histories, one can preliminarily determine the combined design loading and pile geometries which are appropriate for the environments of wind farm selected for the installation of offshore turbine. Secondly, numerical analyses were performed on lateral loading tests of monopile in laboratory and the shaking table of monopile, then compare the results between the simulation and measurement of the tests were made to calibrate the required soil/pile material model parameters. The comparisons show that the simulations of H~h curves, lateral displacement, bending moment distribution of pile shaft, and the acceleration of the pile head are in excellent agreement with the measurements. In addition, the numerical results indicate the utilizatons of Mohr-Coulumn soil model, Hardening soil model with small strain and embedded pile structural element enable a satisfactory simulation of the soil/pile interaction behaviors when subjected to the lateral loading and the acceleration loading.
Subsequently, 3-D numerical models of monopile for offshore turbine were constructed to simulate the soil/pile interaction behaviors subjected to various combined loadings. In numerical model, various pile length L, wind loading Fwind and wave loading Fwave were selected as design parameters to inspect their effects on the dynamic reactions and deformation behaviors of pile foundation. For different design parameters, which includes three pile lengths (L=30, 40, and 50 m) various depth~displacement curves, the various bending moment of pile curve, the acceleration curve and the displacement duration curve of pile head. In addition, a dynamic simulation was carried out on a monopile whne subjected to earthquake loading to inspect the soil/pile interaction responses.
Based on the numerical results, several conclusions can be made:(1) In the process of the simulation on a monopile with vertical static loading and lateral cyclic loading, the influence area of the strata will be larger along with the larger loading. And the mega deformations will appear at the upper strata area.(2) There is nearly no impact on the pile displacement by changing the pile length.(3) As the wind loading constantly getting larger, the displacement and bending moment of pile will become larger. The pile will be easily to meet the tensile failure, and the position of the maximum bending moment will be at the depth L /5 ~ L /3.(4) when the wave loading getting bigger, the displacement and bending moment of pile will become larger. The position of the maximum bending moment will be at the depth 2 L/5 ~2 L/3.(5) During the earthquake simulations, the position range of pile bending moment is between the depth 2 L/5 ~3 L/5.
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