考慮井部分貫穿效應之微水試驗在受限含水層的解

Abstract

微水試驗的方法為在井內瞬間注入或取出一定體積的水，並同時測量井內水位隨時間的變化的數據。本研究提出一個在受限含水層系統中，考慮井部分貫穿效應下的新微水試驗半解析解。首先推求考慮井部分貫穿及蓄水效應的定流量抽水試驗解。隨後，利用Peres et al. (1989) 的關係式，將定流量抽水試驗解轉換為微水試驗的解。所推導的微水試驗解分別與Cooper et al. (1967)的解及Hyder et al. (1994) 所提出的KGS模式做比較。結果顯示，我們的解在完全貫穿井下，能分別與Cooper et al. (1967)的解及KGS模式（Hyder et al., 1994）模擬的結果相符合。但在部分貫穿井時，由於在井緣邊界條件的假設方式不同，使我們的微水試驗解異於KGS模式的模擬結果，若選擇KGS模式來推求含水層參數，則可能會低估水力傳導係數。另外，利用我們所發展的模式，模擬在部分貫穿井內的微水試驗水位反應，發現較小的濾管開口長度、異向性比、或蓄水係數，皆可能造成較慢的水位回復速率。

The slug test is to suddenly remove/ (add) a volume of water from/ (into) a well; and the rate of raise/ (fall) of the well water level is simultaneously measured. This research proposes a new semi-analytical solution for a slug test performed in a partially penetrating well within a confined aquifer system. A constant-flux solution, including well partial penetration and wellbore storage, is first derived and then converted into the slug-test solution via the formula of Peres et al. (1989). The new solution in the cases of well full penetration can reduce to Cooper et al.’s solution (1967) and coincide with the KGS model (Hyder et al., 1994); yet, in regard to well partial penetration, it differs from the KGS model (Hyder et al., 1994) owing to the different assumption on the well boundary condition and the hydraulic conductivity may be underestimated if the KGS model is chosen to identify the aquifer parameters. The simulated results in a partially penetrating well display that a smaller screen length, anisotropic ratio, or storativity can result in a slower recovery rate of the normalized head.