含水層下邊界對於斜井雙極水流試驗影響

The effect from bottom boundary on dipole flow test in a slant well.

李欣融(Hsin Jung Lee)

指導教授 ： 陳家洵

國立中央大學/地球科學學院/應用地質研究所/碩士(2015年)

摘要

傳統地下水調查及整治大多由垂直井進行，若遇到無法進行鑽設垂直井之情況時，可以一定傾角鑽設斜井深入含水層進行相關試驗。其中，雙極水流試驗可解決許多問題（如含水層水文地質參數推估、地下水流場變化、含水層下邊界之影響…等等）。當鑽設斜井時，若含水層厚度較薄，可打成全層貫穿井；但含水層厚度較厚，會造成全層貫穿井施工困難，且花費較高，因此本研究欲探討下邊界對於部分貫穿斜井雙極水流實驗之影響。由於雙極水流試驗是利用雙封塞系統將斜井隔離出上下等長之井篩段，下井篩段以定流率抽水，所抽的水在上井篩段以相同流率注入含水層，容易形成一穩態的循環流場，本研究推導穩態斜井雙極水流試驗模式，求得受壓與非受壓情況下含水層有限厚度與半無限厚度（不考慮下邊界）解。在受壓情形時，當下井篩段至下邊界距離超過0.36倍的含水層厚度，有限厚度模式與半無限厚度模式可完全吻合，可以忽略下邊界的影響。而非受壓情形時，由於不考慮時間變化，其地下水位面邊界條件為定水頭，其結果與受壓含水層相同，其傾角、井篩段長度以及兩井篩中點距離，皆不直接影響兩模式相符程度，因此不論受壓與非受壓，若要打成部分貫穿井，雙極水流試驗設置要使下井篩段至下邊界距離超過0.36倍的含水層厚度，就可忽略下邊界的影響。

關鍵字

斜井 ； 雙極水流試驗

並列摘要

In order to investigate and remediate the aquifer below a building, a slant well at the perimeter of the building is installed and reaches the target aquifer. While drilling slant well, the dipole flow test can measure many parameters more easily such as aquifer hydro geological parameters, estimation of groundwater flow field, bottom boundary of the aquifer, etc. If the aquifer is thin, drilling fully penetrating well will be successful. However, thick aquifer will make drilling entire fully penetrating well more difficult and costly. Therefore, this project wants to discuss the effect from bottom boundary on dipole flow test in a slant partially penetrating well. The slant well is isolated by using a double-packer into two screen sections of equal length. In the upper section, a constant rate pumping is carried out and the withdrawn water is immediately discharge into the lower section, which can create a steady circulation flow field. This study derives the slant well to conduct the dipole flow test in steady state model. It obtains the solution of finite thickness and semi-infinite thickness in confined and unconfined aquifer. In confined aquifer case, when the distance from the lower section to the lower boundary more than 0.36 times the thickness of the aquifer, the models same with limited thickness and semi-infinite thickness. The influence of the lower boundary can be ignored. In unconfined aquifer case, because it do not consider the time change, the water table boundary conditions for the constant head. The result is the same as confined aquifer.

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