海底電纜作為台灣重要對外聯絡的資訊傳輸管道之一，其安全性非常重要。前人研究指出，從2006至2015年期間有2次因颱風過境後所造成的海底電纜斷裂。本研究利用數值模式ROMS，首先基於實驗室的異重流模擬結果進行數值模擬試驗，再分別以不同的紊流閉合模式和底床粗糙度，針對實驗的流速與密度進行模式率定。在率定和異重流模擬相關的紊流模式後，本研究基於高屏溪河川流量歷線、入流泥沙濃度、潮汐及垂向溫鹽分布進行模式設置與結果分析，研究中說明海底峽谷異重流的形成和運輸過程。模擬結果進一步顯示高屏峽谷異重流發生所需的入流濃度遠低於傳統臨界值（40 ~ 45 g/L，低濃度異重流）。當未達入流濃度20 g/L時，泥沙易受到潮汐影響擺動，反之則受河川入流流速影響順下峽谷流。河川入流的流量越大，異重流的流速越快，所產生的分布載重也越大。入流泥沙濃度大於20 g/L時，河川入流濃度越大，異重流的流速越快，產生的分布載重也越大，但入流泥沙濃度對分布載重的影響力不如入流流量。研究中亦針對不同河源泥沙進行情境模擬，結果顯示入流泥沙粒徑越大，沉降速度也越大，導致異重流流速增快，所形成的分布載重也越大，模式結果顯示流速為泥沙沉降速度的1/3次方，符合飽和濃度理論。基於數值模擬結果，本研究建議考慮環境因素和河川入流條件進一步優化電纜的設計規範。

From 2006 to 2015, two instances of submarine cable breaks were caused by the formation of hyperpycnal flow resulting from typhoon passages in southern Taiwan. Therefore, this study utilized the numerical model ROMS for experimental simulations. After model calibration, this research established the model settings. It analyzed the results based on the flow discharge of the Gaoping River, inflow sediment concentration, tides, and vertical temperature-salinity distribution. The study explains the formation and transport process of hyperpycnal flow. The simulation results demonstrate that the required inflow concentration for hyperpycnal flow is much lower than the traditional critical value (40 ~ 45 g/L). Numerical experiments indicate that hyperpycnal flows cannot form when the inflow sediment concentration is below 20g/L. When the inflow sediment concentration is above 20 g/L, a higher river inflow concentration leads to a faster hyperpycnal flow and more significant sediment transport. The study also conducted scenario simulations for different sediment sources, showing that larger sediment grain sizes result in faster settling velocities, leading to faster hyperpycnal flow and more significant sediment transport. Based on the numerical simulation results, the study recommends considering environmental factors and river inflow conditions to optimize cable design specifications further.

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