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題 名 | 抽取地下水導致地層下陷之近似模式=An Approximate Model for Land Subsidence Due to an Overdraft of Groundwater |
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作 者 | 施清吉; 林茹琦; | 書刊名 | 農業工程學報 |
卷 期 | 46:3 2000.09[民89.09] |
頁 次 | 頁11-27 |
分類號 | 443.67 |
關鍵詞 | 地層下陷; 地下水; 擴散方程式; 屏東縣; Land subsidence; Groundwater; Diffusion equation; Pingtung county; |
語 文 | 中文(Chinese) |
中文摘要 | 在適當的假設下,自受壓飽和含水層抽取地下水而導致的地層下陷,其間的控制方程式為一擴散方程式,且含一「源」以代表抽水量。偏微分方程式之分析解可由Green函數構建求得。採用極座標,分析解為一瑕積分包含兩係數--擴散係數D₀與抽水係數N₀。若兩係數之值可估算求得,則分析解可作為近似模式,用於推測不同的抽水量而導致的沉陷量,或在不同的容許沉陷量之容許抽水量。估算方法之一為利用以往兩係數歷線予以推測。歷線之求得係利用分析解及其他相關式,且配合實測與調查資料。實測資料取自沉陷量與地下水位兩觀測井所提供的記錄,而調查資料則來自一個年度的水井普查資料。近似模式應用於屏東縣林邊及其鄰近區域,共分成五個沉陷區(同時也是抽水區):林邊、佳冬、塭豐、水底寮與枋寮。除非是雨量特別豐富的年度,兩係數歷線呈現上升外,其餘的年度,兩係數歷線均呈現緩慢遞減的趨勢,似乎趨近於一定值。以最後三個年度的平均而言,林邊、佳冬、塭豐、水底寮與枋寮的擴散係數D₀分別等於44.34029、282.8512、48.02009、211.7172與147.0063,單位為m²/s;另外,這五區抽水係數No分別等於3.051016、2.958181、3.961396、7.120250與4.600458,N₀為無因次。兩係數值之合理度無法直接判斷,但可間接由其相當的係數判斷之,抽水係數N₀與擴散係數D₀分別與壓縮指標Cс及滲透係數K有關。以受壓飽和含水層之組成係由砂與礫石為主而言,本研究所求得之Cс與K等兩值是合理的,前者大致介於10¯²~10¯³,而後者則介於10¯¹~10¯⁴m/s。 |
英文摘要 | Based on the appropriate assumptions the land subsidence due to an overdraft of groundwater from a confined saturated aquifer is governed by a diffusion equation with a source denoting the pumping discharge. From a Green function, the analytical solution of the partial differential equation can be constructed, which ends up with an improper integral consisting of two coefficients: the diffusivity Do and the pumping coefficient No. If estimated values of these two coefficients can be determined, the analytical solution can be treated as an approximate model for land subsidence to predict the various amounts of land subsidence due to various quantities of pumping discharge or to predict the admissible quantities of pumping discharge under allowable amount of land subsidence. One method of estimation as used in this study is to base on the previous hydrographs of these two coefficients, which are obtained from two aspects: one is the theoretical considerations consisting of the analytical solution and the related functions, and the other is field data of the continuous records of the land subsidence, the elevation of the groundwater and at least a survey of pumping wells for one year. The approximate model is applied to Pingtung Country and its neighbors which is divided into five subsidence or pumping regions: Linpien, Jiadong, Uenfeng, Shueidiliau and Fangliau. Except for some particular years with tremendously great precipitation which will result in a increase of values of coefficients Do and No, the variation of coefficients across each year is generally very small, and it seems that values of these two coefficients will eventually tend to some certain fixed values. Consequently, based upon the later three years the average values of diffusivity Do for Linpien, Jiadong, Uenfeng, Shueidiliau and Fangliau are equal to 44.34029, 282.8512, 48.02009, 211.7172 and 147.0063 in m²/s respectively; the average values for these five regions of the dimensionless pumping coefficient No are 3.051016, 2.958181, 3.961396, 7.120250 and 4.600458 respectively. Values of the coefficients Do and No can not be directly justified, but values of coefficients involving in the definition of Do and No can be justified, in which appeared are the compression index Cc and the permeability K. As long as the confined saturated aquifer which consists mainly of sand and grable is concerned, values of Cc and K obtained in the investigation are reasonable, since they rang from 10⁻² to 10⁻³, and 10⁻¹ to 10⁻⁴ m/s respectively. |
本系統中英文摘要資訊取自各篇刊載內容。