現地導水度試驗評估

Abstract

現地滲透試驗已廣泛的應用在工程上，但是試驗方式與種類繁多，且各種地層之適用性均不相同。本研究除進行雙環入滲儀、兩階段孔內滲透儀、Guelph滲透儀與簡易試驗外，並利用數值模擬分析來評估現地試驗差異之原因。 數值模擬分析係利用FEMWATER軟體，以實驗室所得之滲透係數與土水特徵曲線進行模擬。模擬的過程假設土層為均質，不考慮土層中孔隙與裂縫所造成之影響。 研究結果發現在現地試驗中，Guelph滲透試驗與室內試驗較為接近，簡易試驗、雙環入滲試驗與室內試驗相差較大。對照數值模擬的結果，雙環入滲試驗所得現地滲透係數較不受土層異向性的影響，對Guelph滲透試驗與簡易試驗影響則較大。

In-situ hydraulic conductivity tests have been widely used in field investigations for construction project nowadays. In this study, in order to estimate the cause of various outcomes, in-situ hydraulic testes such as Double-Ring Infiltrometer, Two-Stage Borehole Permeameter, Guelph Permeameter, and Simplified Borehole Test were conducted to compare their applicability in silty and clayey soils. In addition, numerical analysis was performed with a finite-element program, FEMWATER, to further analyze the results of the in-situ tests. The tests were simulated with FEMWATER by using the hydraulic conductivity and soil water characteristic curves obtained from laboratory experiment. The effect of anisotropy of hydraulic conductivity was also studied. Due to the difficulty of quantifying the influence of macropores and fissures in the soils on the hydraulic conductivity, the soils were assumed to be homogeneous. The study showed that the in-situ hydraulic conductivity obtained by the Guelph Permeameter was the lowest and the closest to that from the laboratory tests. On the other hand, the hydraulic conductivity measured by the Double-Ring Infiltrometer tests and Simplified Borehole tests difference were much greater. However, considering the effect of anisotropy and macropores of soil, Double-Ring Infiltrometer test could give more reliable results than Guelph Permeameter and Simplified Borehole Test.