本研究提出一個非耦合沉陷模式，其地下水流模式是引用Neuman和Witherspoon在1969年所提出受限含水層系統之三維半解析解公式，則沉陷模式是採用Terzaghi在1943提出之一維壓密理論。本研究首先進行假設案例分析，其中探討不同幾何參數如:土體厚度和抽水井影響半徑、不同水文地質參數如:水力傳導係數與比儲水係數和土體中阻水層排列於抽水時對水流與地層下陷的敏感度分析，研究結果指出土體愈薄抽水井影響半徑愈小對於地下水流與地層下陷影響愈顯著，其中改變水力傳導係數對地下水流變動最為敏感，而改變比儲水係數則是對地層下陷較為敏感。另一方面，阻水層在土體中排列是厚度薄分佈密集將造成初始沉陷量大且達到穩定的時間快，反之。最後，將此模式應用在台灣雲林縣元長鄉場址，使用乾季地下水位資料且濾除地下水位受到季節性影響再進行模式校正與驗證，並探討乾季抽水對地層下陷之影響。研究結果指出混層抽水用水型態比單層抽水用水型態造成第二含水層地下水流與地層下陷影響顯著，約佔總改變量的97%，而第二含水層抽水比第三含水層抽水所造成第二含水層地下水流與地層下陷影響較大，約佔總改變量的70%。在元長鄉中部地區，第三含水層抽水比第二含水層抽水所造成地層下陷影響較大且混層抽水使用者也比單層抽水使用者對地層下陷造成較大的影響。

This research proposed a decoupled model to analyze subsidence problem. The flow field utilizes analytical solution for pumping in a layered system from Neuman and Witherspoon (1969) to calculate the head drawdown variation. The subsidence estimation apples Terzaghi (1943) consolidation theory to calculate the deformation in each layer. This research starts with sensitivity analysis for various geometrical parameters such as thickness of each soil layer and the radius distance from pumped well. Then, the effect of hydrogeological parameters such as hydraulic conductivity and specific storage are explored on drawdown and land deformation. Afterward, the effect of arrangement of aquitard on land subsidence in a two-way drainage aquitard system is explored. From these analyses, drawdown is found more sensitive to the hydraulic conductivity than to the specific storage in any soil layer. Land subsidence is more sensitive to the specific storage than the hydraulic conductivity. On the other hand, the amount of subsidence is large and the subsidence to reach stable is fast when the arrangement of each aquitard is small. Finally, the proposed model was applied to estimate land subsidence and drawdown variation at the Yuanchang Township of Yunlin County in Taiwan. Groundwater data for dry-season periods were used for calibration and validation. Seasonal effect in groundwater variation was first filtered out. Dry-season pumping effect on land subsidence was analyzed. This research found that the multi-layer pumping contributing is more significant than single-layer pumping on the response of drawdown and land subsidence in aquifer 2 with 97% contribution of total change. The pumping in aquifer 2 contributing is more significant than pumping in aquifer 3 to cause change in drawdown and land subsidence in aquifer 2 with 70% contribution of total change. Pumping at aquifer 3 cause larger land subsidence than pumping at aquifer 2. Multi-layer pumping user contributes more than single-layer pumping user to subsidence in central area of Yuanchang.

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