水非飽和孔隙介質中異質物含量及分佈對V.G.模式參數之影響

The Influence of Heterogeneity on the Parameters of Soil Hydraulic Property Curve in Unsaturated Porous Media

吳呈懋(Cheng-Mau Wu) ； 陳主惠(Chu-Hui Chen) ； 徐年盛(Nien-Sheng Hsu) ； 李振誥(Cheng-Haw Lee)

《農業工程學報》 53卷1期 (2007/03) Pp. 72-81

https://doi.org/10.29974/JTAE.200703.0008

摘要

由於V.G.模式廣泛被應用在實際非飽和孔隙介質中水分傳輸模擬上，利用V.G.模式套配求得之保水曲線(WRC)所得的參數，來估計非飽和水力傳導係數值，這種作法在均質土層中是無庸置疑的。但是在異質性的土層中，由保水曲線θ(h)所得的參數和由非飽和水力傳導係數曲線(UHC)所得的參數是截然不同的。本文用二維飽和及非飽和地下水數值模擬模式(VSAFT2)數值實驗結果顯示異質物含量的多寡會改變土壤水力特性曲線，在相同的實驗土柱，以數值模擬的保水曲線來套配V.G.模式之參數會隨異質物含量的增加而與非飽和水力傳導係數曲線所套配V.G.模式之參數差異越來越大。另外，異質物的排列方式也會改變土壤水力特性曲線，在相同的異質物含量下，異質物的排列方式造成保水曲線及非飽和水力傳導係數曲線所擬合參數的不同，因為排列方式會影響水流流動方向而造成差異。

關鍵字

異質性 ； 土壤水力特性曲線 ； 保水曲線 ； 非飽和水力傳導係數曲線 ； VSAFT2模式

並列摘要

The van Genuchten model (V.G. model) has become one of the most widely used curves for characterizing soil hydraulic properties. Notwithstanding the conclusions that van Genuchten (1980) has made, ”a reasonable description of the Water Release Curve (WRC) at low water contents was important for an accurate prediction of the Unsaturated Hydraulic Conductivity curve (UHC) by comparing five experimental data”, applications of V.G. Model by using parameters of WRC to predict UHC in heterogeneous media are still questioned. This paper used a two-dimensional Variably Saturated Flow and solute Transport finite element model (VSAFT2) to simulate variations of pressure and moisture content in the soil column under a constant head boundary condition. Results show soil hydraulic properties are strongly affected by variation of heterogeneities and their arrangements. Moreover, results reveal that parameters estimated from both WRC and UHC are also affected by patterns of heterogeneity; this indicates that the parameters obtained from the WRC are not suitable for predicting the UHC in different patterns of heterogeneous media.

並列關鍵字

Heterogeneity ； Soil hydraulic property curve ； WRC ； UHC ； VSAFT2