邊界條件及滲漏補注對地下水流分數維度之影響

The influence of boundary conditions and leakage on the fractional groundwater flow dimensionality

劉宜諺(Ｙi-Yen Liu)

指導教授 ： 陳家洵

國立中央大學/地球科學學院/地球物理研究所/碩士(2006年)

摘要

裂隙含水層普遍存在地表之下較深處，當進行水力實驗以分析裂隙含水層水文地質狀況時，需要選用合適之水井水力學模式。廣義徑向流模式以地下水流分數維度描述地下水流經截面積隨距離之變化，為分析裂隙含水層水文地質特徵常用模式之ㄧ。壓力微分大時間斜率可用以分析廣義徑向流模式之地下水流維度，但用以分析受定水頭邊界、不透水邊界及滲漏補注洩降資料之地下水流維度並非完全正確。本研究以標準曲線匹配方式，分析徑向流在單一定水頭邊界、單一不透水邊界及滲漏補注之地下水流維度，並與壓力微分大時間斜率分析結果比較，證實壓力微分大時間斜率不適用於分析非碎型幾何模式之地下水流維度。此外，進一步分析二互相垂直不透水邊界、互相垂直定水頭邊界、二互相垂直之不透水及定水頭邊界洩降，發現二互相垂直不透水邊界洩降變化完全不符合廣義徑向流模式，而其他不同水文地質邊界與滲漏補注洩降資料，所得地下水流維度非唯一，水力傳導係數及比儲水係數值隨地下水流維度增加而減小，且均不等於真實值，顯示邊界條件與滲漏補注無法由地下水流分數維度吸收。加入邊界條件時，已不滿足廣義徑向流模式需保持徑向流之特性。因此邊界條件與滲漏補注以廣義徑向流模式代表並無意義。

關鍵字

地下水流分數維度 ； 邊界條件 ； 滲漏補注 ； 壓力微分 ； 標準曲線匹配

並列摘要

The problem that arises when analyzing data from a hydraulic test is that of choosing an appropriate geometry for the fractured system into which flow occurs. Generalized radial flow model which considers fractional dimensions is a common method to analyze the hydraulic test data in fractured aquifer. The late-time slope of the pressure derivative can aid to determine the flow dimensions of generalized radial flow model, but it is not totally correct to determine the flow dimensions of the hydrogeologic conditions, including constant head boundary, impermeable boundary, and leakage. We analyze the flow dimensions of the radial flow with a linear constant head boundary, a linear impermeable boundary, and leakage by type curves fitting, and compare with the analyzing results by the late-time slope of the pressure derivative. According to the comparisons, we prove that the late-time slope of the pressure is not suitable to determine the flow dimensions of nonfractal model. Moreover, we also analyze the drawdown data of radial flow with two perpendicular constant head boundaries, two perpendicular impermeable boundaries, and a constant head boundary perpendicular to an impermeable boundary. The drawdown date of two perpendicular impermeable boundaries can not match generalized radial flow model. The flow dimensions of other boundary conditions and leakage are not unique, and the hydraulic conductivity and the specific storage do not equal to hypothetical values. The boundary conditions and leakage can not be substituted by variable flow dimensions.

並列關鍵字

boundary conditions ； leakage ； pressure derivative ； type curves fitting ； fractional dimension

參考文獻

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