本文關(guān)鍵詞： 海底地下水排泄(SGD) 鹽度分布 密度差異 坡度 穩(wěn)定態(tài)數(shù)值模擬　出處：《中國(guó)地質(zhì)大學(xué)(北京)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：海底地下水排泄和海水入侵是兩個(gè)相互作用、相互影響的處于動(dòng)態(tài)平衡的過程,為了進(jìn)一步了解穩(wěn)定狀態(tài)下均質(zhì)各向異性潛水含水層中海水與地下水之間的相互作用,本文利用數(shù)值模擬法重點(diǎn)研究了滲透系數(shù)、各向異性比、縱橫向彌散度之比和海底坡度對(duì)含水層中鹽度分布和海底地下水排泄量的影響。其中,滲透系數(shù)的變化范圍為10-9m/s~1m/s(弱透層到含水層、粘土層到礫石層),各向異性比的取值范圍為1~100,縱橫向彌散度之比的取值范圍為1~500,海底坡度的變化范圍為0.01~?2(弧度)。模型區(qū)域內(nèi)陸邊界為給定水頭邊界、鹽度為零,區(qū)域底部為隔水邊界,上邊界(地表)為不考慮降雨和入滲的隔水邊界,海向邊界的壓力水頭為作用于其上的海水水柱的壓強(qiáng),當(dāng)海水流入含水層時(shí)為給定濃度35g/L,當(dāng)水流流出含水層時(shí)為零彌散邊界條件。采用二維數(shù)值代碼MARUN來求數(shù)值解,空間離散采用三角形有限單元法,依據(jù)海底坡度的不同,所考察區(qū)域的海向延伸長(zhǎng)度不等,結(jié)點(diǎn)數(shù)在16605到41123間變化,三角形單元數(shù)在32320到80160之間變化,網(wǎng)格的Peclet數(shù)均小于2,Courant數(shù)小于0.95,計(jì)算過程采用Picard迭代法,壓力水頭迭代收斂標(biāo)準(zhǔn)為10-5m。研究結(jié)果表明:當(dāng)zx L?KK?10-6m2/s時(shí)(其中zK是垂直滲透系數(shù)、L?是縱向彌散度),鹽度的空間分布幾乎獨(dú)立于水平滲透系數(shù)xK,且此時(shí)地下淡水排泄量fQ和海水再循環(huán)量sQ均與水平滲透系數(shù)xK呈線性關(guān)系,同時(shí)用一個(gè)半解析方法驗(yàn)證了這一系統(tǒng)性結(jié)論;各向異性比增大時(shí),咸淡水界面向海向移動(dòng)、并使海水再循環(huán)量sQ減小,消除了相關(guān)文獻(xiàn)對(duì)此的爭(zhēng)議;給定縱向彌散度后、增大縱橫向彌散度之比會(huì)使混合帶變傾斜并降低海水再循環(huán)量sQ;當(dāng)海底坡度?從0.01增大到?2時(shí),咸淡水混合帶會(huì)向內(nèi)陸方向移動(dòng),當(dāng)??4時(shí),海底坡度?的增大會(huì)使海水再循環(huán)量sQ有輕微的增加,當(dāng)??4時(shí),海底坡度?的增大會(huì)降低海水再循環(huán)量sQ。這些研究結(jié)果填補(bǔ)了前人在研究穩(wěn)定態(tài)海水-地下水相互作用時(shí)時(shí)尚存的空白,進(jìn)一步對(duì)影響SGD的因素進(jìn)行了挖掘與分析,具有重要的意義。
[Abstract]:Undersea groundwater discharge and seawater intrusion are two interactive, interactive processes in dynamic equilibrium, in order to further understand the interaction between seawater and groundwater in homogeneous anisotropic aquifers in a stable state. In this paper, the effects of permeability coefficient, anisotropy ratio, longitudinal and transverse dispersion ratio and submarine slope on salinity distribution and groundwater discharge in aquifers are studied by numerical simulation. The variation range of permeability coefficient is 10-9 m / s / s (weak permeability layer to aquifer, clay layer to gravel layer), anisotropy ratio is in the range of 1 ~ 100, longitudinal and horizontal dispersion ratio is in the range of 1 ~ 500, and the variation range of submarine slope is 0.01? 2 (Radian). The inland boundary of the model area is a given head boundary, the salinity is zero, the bottom of the region is a water-barrier boundary, and the upper boundary (surface) is a water-barrier boundary that does not take into account rainfall and infiltration. The pressure head of the sea boundary is the pressure of the water column acting on it. When the seawater flows into the aquifer, it is 35 g / L of given concentration, and when the water flows out of the aquifer, it is a zero dispersion boundary condition. The numerical solution is obtained by using the two-dimensional numerical code MARUN. The spatial discretization adopts the triangular finite element method. According to the difference of submarine slope, the length of sea direction extension varies from 16605 to 41123, the number of triangular elements varies from 32320 to 80160, the number of nodes varies from 16605 to 41123, and the number of triangular elements varies from 32320 to 80160. The Peclet number of the grid is less than 2? Courant number less than 0. 95. The Picard iteration method is used in the calculation process, and the convergence criterion of pressure head iteration is 10 ~ (-5) m. The results show that: when ZX L? KK? 10-6 m2 / s (where ZK is a vertical permeability coefficient L? The spatial distribution of salinity is almost independent of the horizontal permeability coefficient (XK), and there is a linear relationship between the underground fresh water discharge (f Q) and the seawater recirculation volume (sQ) with the horizontal permeability coefficient (XK), and the spatial distribution of salinity is almost independent of the horizontal permeability coefficient (XK). At the same time, a semi-analytical method is used to verify this systematic conclusion. When the anisotropy ratio increases, the salt-water interface moves toward the sea and decreases the seawater recirculation volume (sQ), which eliminates the controversy in the relevant literature. Increasing the ratio of longitudinal and transverse dispersion causes the mixing zone to be tilted and reduces the seawater recirculation sQ. when the seabed slope is? From 0.01 to? 2:00, the salt and fresh water mixing zone will move inland, when? ? 4:00, bottom slope? The increase of seawater recycling volume (sq) will cause a slight increase in seawater recirculation volume (sq). ? 4:00, bottom slope? These results fill the gaps in the previous researches on the interaction between seawater and groundwater in a stable state, and further excavate and analyze the factors affecting SGD, which is of great significance.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P641;P731.2

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相關(guān)期刊論文 前1條

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本文編號(hào)：1555466