質點於破裂面介質中傳輸情形之研究

A Study of Modeling Mass Transport in Fracutred Media With Emphasis on Dispersivity

李振誥(Cheng-Haw Lee) ； 程繼民(Chi-Min Cheng) ； 余進利(Jin-Li Yu)

《鑛冶：中國鑛冶工程學會會刊》 36卷2期 (1992/06) Pp. 75-84+92

摘要

本文主要探討地下水污染物傳輸程度與破碎岩體之水力參數間的關係。在本文中以延散度定量地下水傳輸質點程度之大小，並利用統計機率方法發展一套可有效模擬地下水流動與傳輸之離散破裂面數值模式，並與前人所發展出之連續模式的解析解相比較，並評估其優劣點。結果顯示，本模式除可涵蓋前人之連續模式外，亦可利用破裂面參數隨機分佈特性來探討延散度，結果指出，延散度與地下水之水力梯度大小與方向，岩體破裂面之間距、夾角、內寬、孔隙率與透水係數，以及延散時間與規模有關。同時，當取樣規模大小為最大平均間距24倍時，延散度將可達一穩定值。

並列摘要

This paper provides a qualitative comparison of dispersivity calculated from a discrete fracture model with an analytical solution (de Jong model) in fractured rocks, which involve two sets of parallel, planar and continuous fractures intersecting at various angles. The discrete fracture model invloves two spacing cases of a constant value and a negative exponent distribution. Results show that dispersivity is related to the direction of hydraulic gradient, fracture aperture, spacing and fracture hydraulic conductivity. The value of the calculated dispersivity using the discrete fracture model with constant fracture spacing agrees with that using the analytical solution after the scale effect is ommitted. The discrete fracture model with the spacing of negative exponential distribution can be used to determine the uncertainty of dispersivity due to the variation of the spacing. Result also indicates that the effect of scale on dispersivity can approach to a constant value after particles have travelled about 24 times the maximum average fracture spacing.