地層下陷在台灣西南沿海平原是一種常見的地質災害，其根本原因在於台灣水資源乾濕季分布不均，且農業、工業和養殖業等活動快速增長所帶來對水資源的急劇需求，這股需求使得地下水成為一種相對容易取得和成本效益高的水源，尤其於雲彰地區其水源來源大多來自地下水。然而，這也同時引發了許多平原地區過度抽取地下水的問題，造成超額孔隙水壓消散，有效應力逐漸增加，壓實土壤骨架減少孔隙空間，最終導致嚴重且不可逆的地層下陷，影響高鐵等重大建設之安全風險增加，維護成本提高，近十年雖然雲林彰化地區沉陷量已呈趨緩趨勢，但109年雲林下陷速率仍高達5.5公分/每年，而彰化沉陷速率也達到了5公分/每年，為了更進一步理解抽水與沉陷之行為關係，本研究於地下水位觀測井進行抽水試驗，同時以分層水位井記錄不同深度土層間的水位變動，並進行不同時間長度的抽水試驗，根據Lo et al.(2014)應用Lo et al. (2005)所提出之多孔彈性介質中含不相容、可壓縮且具有黏滯性流體的孔彈性理論方程式推導出之非飽和土壤壓密理論，將其簡化為一維土壤壓密之解析解，應用分層水位井記錄地下水位觀測井進行抽水試驗之數據於此解析解方程式與磁環地陷井量測值進行比較。
研究結果顯示，淺層土壤在抽水過程中，由於前期土層的解壓行為會導致壓密行為無法完全準確計算，且土壤有遲滯現象，導致解析解在計算上容易高估沉陷量。由分層水位井的觀測及計算的數據結果，土層變化趨勢與磁環地陷井量測之結果一致，不僅驗證了水位分層井及孔隙彈性理論模型的適用性，也在實際應用中發現無論是計算砂土層佔比較多處與黏土及粉土層處之沉陷量會有高估現象發生，於黏土層尤為顯著。

Land subsidence is a common geological disaster primarily caused by excessive groundwater extraction. This issue has led to severe and irreversible land subsidence in many plain areas, increasing the safety risks for major constructions, such as high-speed rail, raising maintenance costs, and causing land loss. Therefore, this study conducts pumping tests at groundwater observation wells, recording water level changes at different soil depths using the Multi-Channel Wells. Pumping tests are carried out for varying durations to observe the effects over different time periods. The soil consolidation theory based on the poroelastic equations proposed by Lo et al. (2014) for an elastic porous medium containing an incompatible, compressible, and viscous fluid, is simplified into a one-dimensional analytical solution. The water level data from the multi-channel wells are incorporated into this analytical solution equation, and then compared with the measurements from the multi-level compaction monitoring wells.
The results obtained by our study reveals that during the pumping process, decompression of the initial soil layers and hysteresis leads to less accurate consolidation calculations, often overestimating subsidence. Nonetheless, data from the multi-channel wells closely aligns with measurements from the multi-level compaction monitoring wells, confirming the validity and applicability of both the multi-channel wells and the theoretical consolidation model of poroelasticity.

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