台灣中南部平原地區飽受地層下陷影響，引致地上建築物損害、防災設施設計高不足及海水倒灌等問題，近年以雲林地區最嚴重。對於地層下陷問題，常使用Terzaghi單向度壓密理論進行解釋與預測，當地下水位升降時，其現地水力邊界會隨者時間變動，與傳統單向度壓密理論不符；此外，在現地複雜土層下，水位變化引起之依時壓密量難以估算，因此，阻水層等低滲透性材料受孔隙水壓波動引致依時壓密變化機制有待釐清。本研究以Rowe壓密儀系統，針對現地鑽探取樣之阻水層材料，利用壓密理論之時間因子進行室內實驗試體與現地土層厚度之時間尺度轉換，將現場之地下水位觀測資料作為土樣試體加載條件，模擬現地水力與應力邊界變化，並比對磁環分層式地層下陷監測井監測數據，擬合等值之現地排水路徑長。試驗結果證明阻水層之壓縮機制是由地下水位升降所激發之超額孔隙水壓消散後所引致，屬壓密中狀態，在阻水層之現地等值排水路徑具代表性下，試驗結果可作為未來不同水位變化下阻水層沉陷預測之依據。

Land subsidence is often explained and predicted using Terzaghi's one-dimensional consolidation theory. However, the hydraulic boundary conditions in the field change over time, which is inconsistent with traditional one-dimensional consolidation theory. Therefore, the time-dependent consolidation mechanism of low-permeability materials, such as aquitards, induced by fluctuations in pore water pressure, needs to be clarified. To clarify the mechanism of ground subsidence in Yunlin area, this study utilizes groundwater level observation data, converting it into equivalent effective stress changes, to conduct variable loading tests on clay. The results are compared with data from a multi-level compaction monitoring well to estimate an equivalent drainage path in the field. This approach clarifies the subsidence mechanism of aquitards induced by groundwater level fluctuations and establishes a reliable prediction of time-dependent subsidence in aquitards.The test results demonstrate that the compression mechanism of aquitards is induced by the dissipation of excess pore pressure triggered by groundwater level fluctuations. When the equivalent drainage path in the aquitard remains unchanged, the test results can serve as a basis for predicting future subsidence of aquitards under different groundwater level changes.

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