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題名 | Rainfall Characteristics for Anisotropic Conductivity of Soil Slope=降雨特性對水力傳導異向性土壤邊坡之研究 |
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作 者 | 葉信富; 沈岡陵; 李振誥; | 書刊名 | 中華防災學刊 |
卷期 | 7:1 2015.02[民104.02] |
頁次 | 頁93-108 |
分類號 | 442.3 |
關鍵詞 | 降雨特性; 異向性傳導; 信賴度指數; 邊坡穩定; Rainfall characteristics; Anisotropic conductivity; Reliability index; Slope stability; |
語文 | 英文(English) |
中文摘要 | 本研究在邊坡穩定分析中,考慮各種變數或參數本身之變異性,利用邊坡穩定可靠度分析模式,評估邊坡破壞機率及信賴度指數(reliability index)來判定邊坡穩定。本研究設計不同研究案例,應用數值分析軟體Geo-Studio模擬降雨入滲至未飽和均質土壤邊坡內部,以SEEP/W套件進行暫態分析,再將所得的孔隙水壓資料代入SLOPE/W套件分析邊坡穩定,進而探討不同的降雨特性對於異向性水力傳導邊坡的影響機制。研究案例結果指出,不同土壤邊坡於降雨事件發生時,砂土邊坡安全係數下降幅度最大,次為粉土,最後為黏土邊坡。而分別在前峰、中峰及後峰不同雨型的狀態下,對於邊坡穩定發生下降的時間影響最為顯著,穩定性下降時間先後順序為前峰雨型、中峰雨型,最後為後峰雨型。在探討異向性水力傳導的案例中,結果顯示砂土邊坡對於水力傳導係數的異向性最為敏感,水力傳導係數的異向性對於黏土邊坡的影響不甚顯著。最後,本研究考量當降雨強度改變下,土壤水力傳導係數大於降雨強度時,於降雨事件開始信賴指數就發生明顯下降,於降雨事件開始6小時後,下降幅度趨於平緩,下降為初始信賴指數的23%。另外,當土壤水力傳導係數小於降雨強度時,降雨入滲發生時,信賴指數有一段7小時的遲滯,其後發生一大幅度的下降,下降為初始信賴指數的65%。本研究模擬結果指出當氣候變異造成一強降雨發生時,如果土壤水力傳導係數小於降雨強度時,邊坡發生不穩定的時間會相對降雨強度小較早發生。本研究之分析結果可以提供坡地防災之參考。 |
英文摘要 | In this study, probability analysis was used to evaluate the stability of unsaturated soil slopes. The finite element computer program Geo-Studio was used to simulate the process of rainwater infiltrating a slope. The pore-water pressure results evaluated from seepage analysis (SEEP/W) were imported into the slope stability program (SLOPE/W). Results for the anisotropic ratio of hydraulic conductivity indicate that when the anisotropic ratios become higher, the reduction in the reliability index is insignificant. Cases for a sand slope under different rainfall intensities (I) were designed. It was found that when saturated hydraulic conductivity (k_s) was greater than I, the reliability index decreased immediately; further, there was also a decrease in the reliability index by nearly a quarter and the event after 6 hours remained stable. When ks was less than I, the reliability index remained at the beginning level; however, about 7 hours later, a marked downward trend was found, and the reliability index fell by 65%. In the first of two cases, the simulation results indicated that when k_s was less than I, the percentage probability of the occurrence of a landslide was larger than when k_s was greater than I. Finally, in the cases of anisotropic k_s, stability of the high ratio soil slopes was not found to be sensitive to the reliability index variation during the simulation period. Moreover, when k_s was greater than I, slope stability decreased earlier than was the case in the opposite situation. |
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