我國近期積極開發離岸風力發電，目前商轉之離岸風機多以大口徑單樁為主要支撐結構。於開發前期，開發商一般僅對海床土壤進行少量鑽探作業，因此，進行基礎概念設計時，須考量地工設計參數不確定性對大口徑單樁基礎穩定性的影響。
本研究以蒙地卡羅法考量土壤參數不確定性對大口徑單樁結構的影響，以Peck(1953)工程土壤分類方法，依標準灌入試驗SPT-N值，將現有公開之離岸風場鑽探資料分類為16種工程土壤，由統計方法(包含K-S test、Q-Q plot及直方圖)判斷各土壤種類適用之機率密度函數，依照不同的機率密度函數的條件，生成多筆亂數模擬土壤參數之變異性。經由建立SPT-N與地工參數之推估關係式，給定土壤強度參數，完成地工參數隨機給定模型。本研究參考黃昱睿(2018)建立離岸風機大口徑單樁基礎有限元素數值模型之方法，由地工設計參數隨機給定模型給予數值模型土壤強度參數，分析一千組隨機案例。為縮短分析時間及減少人力成本，本研究建立樁土互致行為自動化分析模組，此模組可由地工參數隨機給定模型中之材料組合，更新數值模型中的土壤地工設計參數。樁土互致行為自動化分析模組可自動化計算更新材料參數後的數值模型，並儲存檔案。計算完預定分析組數後，可自動輸出大口徑單樁基礎之樁頭位移量，並且計算各分析案例之樁身旋轉角。本研究除了以蒙地卡羅法分析地工設計參數不確定性對大口徑單樁基礎之穩定性影響外，同時計算各工程土壤之標準灌入試驗SPT-N特徵值，定義各工程土壤SPT-N之上下限，於給定地工設計參數上下限的條件下，進行大口徑單樁基礎受力變形反應定量分析，作為與地工參數隨機給定模型分析大口徑單樁基礎穩定性之成果比對參考。
於本研究給定之案例分析條件下(基樁8m，樁長50m)，參考風場各類工程土壤SPT-N的變異係數為20%-50%，而經由基樁受力變型行為自動化分析後，其樁頭變形量之變異係數為3%，且樁頭旋轉角皆低於DNV. GL(2016)建議之SLS設計條件的0.25°。此外，樁頭位移量超出上下限的案例發生機率落在0.32%及0.84%，即超出本研究定義之上下限案例的發生機率極低，顯示給定之案例分析條件大口徑單樁基礎設計尺寸較為保守。

It’s important to grasp the soil properties in the beginning of offshore windturbine development. Before the windturbine design and construction, developers can only assemble the risk of the development though the limit borehole data. They will face the problem of the soil uncertainty. In order to deal with the soil uncertainties, in this research, use statistic method to test the probability distribution of Standard Penetration test value (SPT-N). Simulate the soil uncertainties though Monte Carlo Method and following the engineering soil type PDF create the random database for SPT-N. PLAXIS 3D numerical model is used to analysis the behaved of the monopole foundation in the study. To analysis the effect of the monopile foundation stability under the soil uncertainties condition, this study create the auto PLAXIS program through PYTHON. This program can automatically update the soil strength parameter, which is created in random database, for each numerical model case. It can save large time and work for the whole case study. The case study result show that the variance of the monopile deformation is not signification as considering the soil uncertainties through modifying the soil strength parameters. In the future study, it can consider the soil deformation parameter to simulate the soil more reality.

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