臺南科學園區霞客湖滯洪池於2019年4月清疏作業期間，發現側溢堰某區段出現長約30公尺之邊坡土石破壞。經排除凹岸沖刷與水躍影響後，初步研判係因降雨導致側溢渠道與滯洪池間產生水頭差（側溢渠道水位高於滯洪池），滲流將土中細粒帶走形成管湧，進而造成堰體滲流破壞。
本研究旨在驗證上述滲流破壞機制，並提出相應工程對策。經彙整國內外文獻與技術資料，明確指出滲流破壞成因及檢核方法。初步以滲流線分析與曼寧公式計算流速，結果均符合安全規範，進一步採用萊因氏（Lane）權重緩流比進行滲流安全性檢核。
由於萊因氏分析需掌握土層類型，遂進行地質鑽探並採集樣本，委由SGS實驗室進行土壤物理性質試驗，經大地技師審閱岩心與數據，繪製鑽孔柱狀圖，並記錄標準貫入試驗（N值）結果。試驗顯示場址為砂、粉土與黏土混合層，依比例加權計算後，以較保守之BH-1鑽孔權重緩流比7.08作為分析基準。
分析結果顯示，側溢堰原基腳深度0.6公尺及整治後1.2公尺皆不符安全需求，需加深至1.8公尺方能達到安全標準（權重緩流比7.15 > 7.08）。惟考量RC基腳造價高且施工困難，建議採用塑鋼板樁作為截水工法，兼顧經濟性與施工可行性，並有效抑制管湧破壞。
本研究期間亦經歷2024年7月之凱米颱風侵襲，災後檢查發現側溢堰不同區段出現貫穿性破壞，且沖蝕方向由側溢渠道向滯洪池延伸。地質鑽探顯示堰體區域標準貫入試驗N值僅3，壓實度不足，另護岸採用生態工法亦可能遭受生物築巢侵蝕。綜合上述，建議針對堰體結構全面補強，並導入無人飛行載具（UAV）進行建模監測，搭配人工定期巡檢機制，以利早期發現異常並即時處置。

When Xiake Flood Detention Pond in Tainan Science Park was being dredged in April of 2019, a 30 meter landslide was found along the revetment of a side overflow weir. After the possible causes of concave bank scouring and hydraulic jump were overruled, the initial analysis identified the cause of spillway failure as piping failure. First, raining caused water head difference (which made the water level in side overflow weir higher than that in flood detention pond), so the seepage occurred in nearby area. The piping failure formed in the soil when seepage washed away finer-grained soils.
The objective of this research is to investigate the mechanism of the piping failure of revetment and provide engineering solutions. A summary of domestic and international literature and technical data explicitly identified the causes and investigation method of piping failure. The preliminary flow velocity calculations with seepage line and Manning's equation showed compliance with safety requirement. Hence, advanced safety check was performed with Lane's weighted creep ratio of subcritical flow.
The classification of soil was necessary in Lane's analysis. Hence, boring samples were examined with Soil Physical Property Test at SGS laboratory. Geotechnical engineers reviewed boring cores and data to draw boring logs and record results of Standard Penetration Test (N value). The examinations showed the sampling site was a mixture layer of sand, silt and clay. The more conservative weighted creep ratio of boring sample BH-1 is about 7.08.
The investigation results showed that both the footing length of original weir (0.6m) and refurbished weir (1.2m) didn't meet the safety requirement. The required footing length is 1.8m which made weighted creep ratio of 7.15, laager than 7.08. However, the Reinforced Concrete footing is expensive and difficult to build. So this research recommended that the footing of fiber-reinforced plastic (FRP) sheet pile as the more economic and easier to construct solution for inhibiting piping failure.
The safety check after Gaemi Typhoon in July, 2024 found that several penetration failures at different sections of the side overflow weir. The scouring direction extends from the side channel to flood detention pond. The N value of Standard Penetration Test was merely 3, which showed that the compaction of soil didn't satisfy requirement. In addition, it is possible that biological nesting was encroaching the ecological engineering of the weir. Based on the above results, this research recommends a comprehensive reinforcement of the spillway structure. Visualized modeling with UAV and regular safety monitoring by human eyes are also recommended.

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