| 摘要: | 多深度微水試驗(MLST)可用於測定含水層中水力傳導係數的垂直分布K(z)，在建立MLST的模型時，依照井篩邊界條件假設的不同，分別建立了均勻水頭模式(UH)和均勻流量模式(UF)，同時我們將薄壁效應加入模式中，分析正薄壁與負薄壁效應對UH模式與UF模式的影響。正薄壁效應是由於鑽井時鑽泥入侵井周圍的土壤孔隙，使井邊地質材料透水能力下降，而我們利用正薄壁因子Sk來表示正薄壁效應的影響。負薄壁效應則是井設置完成後浣井過度，造成井邊土壤顆粒遭到掏洗而使井邊地質材料透水性增加，而我們利用有效井管半徑re來模擬負薄壁效應的影響。利用不同Sk與re搭配部分貫穿比 、垂直異向比 和扁平比 的組合來比較UH模式與UF模式之間的差異，發現(1)在非均勻薄壁效應的狀況下，測試段的離散數目不影響井內的水頭反應；(2)在非均勻薄壁效應的分布情況，可以利用一種平均的方法來取得最相合的平均薄壁因子，但依照薄壁效應的分布情況不同，使用的平均方法也會不同；(3)當正薄壁效應時，UF與UH模式相合；在負薄壁效應時， 越小、 越小與 越大的狀況下，UF與UH模式越不相合。;The multilevel slug test (MLST) is an in-well technique in characterizing the vertical distribution of hydraulic conductivity K(z) in aquifer. In modeling MLST, the well screen is either simulated as a uniform-flux (UF) or a uniform head (UH) condition. This study investigates the impact of the skin effect, positive or negative, on the UH and UF models. The positive skin effect, as associated with a reduced hydraulic conductivity surrounding the well due to drilling mud invasion, is taken into account by making use of a skin factor, Sk. The negative skin effect, as associated with an increased hydraulic conductivity due to overdeveloping of the well, is modeled by using an effective well radius, re, which is greater than or equal to the well radius, rw. The UF and UH models are compared using different values of Sk and re for a variety of the partial penetration ratio of screen length to aquifer thickness, , the vertical anisotropy ratio of hydraulic conductivity, , and the aspect ratio of rw to the screen length, . It is found that (1)For positive skin, UH and UF models yield the same results for both high- and low-K conditions, (2)For negative skin (-3<sk<-1), a="" and="" of="" for="" partial="" on="" non-uniform="" to="" the="" or="" highly="" vertical="" an="" sk(z)="" exists="" relationship="" unique="" no="" sk(z).="" distribution="" dependent="" is="" their="" but="" results,="" same="" yield="" able="" uniform="" apparent="" sk(z),="" place="" (3)in="" κ,="" ratio,="" anisotropy="" larger="" ,="" penetration,="" smaller="" α,="" aspect="" pronounced="" more="" becomes="" models="" uf="" uh="" between="" existing="" discrepancy="" td="" .<=""></sk<-1),> |
