本文關鍵詞： 地下水空氣擾動(AS) 高密度電阻率法(ERT) 空氣流型 空氣流動模型　出處：《吉林大學》2016年碩士論文　論文類型：學位論文

【摘要】：地下水空氣擾動(AS)是一種新興污染地下水原位修復技術,該技術被認為是去除非飽和區(qū)帶土壤和淺層地下水中揮發(fā)性有機污染物的最有效方法之一,其優(yōu)勢在于成本低、效率高、可操作性較強。但是關于污染場地AS處理過程中的物理、化學、生物及復合作用的相關機理尚不明晰,地下水空氣擾動修復系統(tǒng)相關設計參數(shù)多為經(jīng)驗估計,而對于AS運行作用機制的理論研究更不完善。地下水空氣擾動AS修復過程中,空氣在飽和多孔介質中的流動機制及影響范圍是污染地下環(huán)境中修復效率的主要影響因素。傳統(tǒng)的空氣擾動影響區(qū)域(ZOI)監(jiān)測方法為場地布井實驗,一般依賴于鉆井、樣品溶解氧測定和地下水位監(jiān)測等手段,監(jiān)測成本高、人員需求量大、監(jiān)測反應速度較慢、不宜考慮非均質介質,同時對場地的土地利用帶來了不可忽視的破壞性擾動。因此,本文以高密度電阻率法(ERT)這一無損的非擾動地電學勘探方法為主要手段,構建該方法在地下水空氣擾動監(jiān)測中的應用路徑,并以多相流體力學為理論基礎對AS進行研究,建立了二維實驗砂槽中不同粒徑均質玻璃珠(GBS)飽和介質中空氣流動模型。本文采用高密度電阻率法(ERT)為主要監(jiān)測手段,通過控制多孔介質材料分選性、粒度級配、空氣擾動流量等室內實驗變量,對AS氣體流型、范圍及空氣飽和度動態(tài)分布進行研究。結果表明,高密度電阻率法(ERT)在AS監(jiān)測中具有很好的靈敏度及準確性,且測試較為方便快捷。介質中空氣擾動壓力與氣體流量呈線性正相關關系;分選性較好的均質介質中氣體飽和度以曝氣口中心所在橫截面對稱分布,中心飽和度較大;非均質中氣體遇到滲透性小的區(qū)域時氣體會聚集,并選擇少數(shù)通道優(yōu)先通過。曝氣流量較大時,氣體易橫向漂移,局部優(yōu)先流容易形成。同時,在不同粒徑的均勻介質中,空氣擾動范圍主要受空氣擾動注氣流量及壓力影響,與粒徑無關,但氣流形式受粒徑影響。3 mm均勻玻璃珠介質中,氣體以氣泡形式向上運動;1 mm均勻玻璃珠介質中氣體流動方式為微通道式;0.5 mm均勻玻璃珠介質中,氣體仍以微通道形式運動,但氣流通道相對分散且彎曲。而在非均勻介質中,氣體主要為槽式流,以塊區(qū)域形式出現(xiàn)。以室內實驗條件構建物理模型,在Darcy定律和Bessel函數(shù)理論變換基礎上,結合水土特征曲線中的Fredlund和Xing(FX)模型與van Genuchten(VG)模型,本文提出了二維砂槽實驗條件下的AS軸對稱空氣流動模型,并利用室內AS實驗對該模型進行驗證。
[Abstract]:Groundwater air disturbance (ASA) is a newly developed in situ remediation technology for polluted groundwater, which is considered to be one of the most effective methods to remove volatile organic pollutants from unsaturated zone soil and shallow groundwater. Its advantage lies in its low cost. However, the mechanism of physical, chemical, biological and compound action in the process of as treatment of contaminated site is not clear, and the related design parameters of groundwater air disturbance remediation system are mostly estimated by experience. However, the theoretical study on the mechanism of as operation is far from perfect. In the process of groundwater air disturbance as remediation, The flow mechanism and influence range of air in saturated porous media are the main influencing factors of remediation efficiency in polluted underground environment. By means of sample dissolved oxygen determination and groundwater level monitoring, the cost of monitoring is high, the demand for personnel is large, the monitoring reaction is slow, it is not appropriate to consider heterogeneous media, and at the same time, it has brought a destructive disturbance to the land use of the site. In this paper, the high density resistivity method (ERT), a non-perturbed geoelectric exploration method, is used as the main means to construct the application path of this method in the monitoring of groundwater air disturbance, and based on the theory of multiphase hydrodynamics, as is studied. A model of air flow in saturated medium with different sizes of homogeneous glass beads in a two-dimensional experimental sand tank is established. The high density resistivity method (ERT) is used as the main monitoring method to control the material sorting and particle size gradation of porous media. The dynamic distribution of as gas flow pattern, range and air saturation are studied by using indoor experimental variables such as air disturbance flow rate. The results show that the high density resistivity method has good sensitivity and accuracy in as monitoring. The air disturbance pressure in the medium has a linear positive correlation with the gas flow rate, and the gas saturation in the homogeneous medium with good sorting is symmetrical distribution in the cross section of the aeration center, and the center saturation is larger. When the gas in heterogeneity meets the low permeability area, the gas accumulates and chooses a few channels to pass first. When the aeration rate is high, the gas tends to drift laterally, and the local preferential flow is easy to form. At the same time, in the homogeneous medium with different particle sizes, The range of air disturbance is mainly affected by the gas injection rate and pressure of air disturbance, which is independent of the particle size, but the air flow pattern is affected by the particle size in the homogeneous glass bead medium. The gas moves upward in the form of bubbles in a 1 mm uniform glass bead medium. The gas flow pattern is in the microchannel type of 0.5 mm uniform glass bead medium. The gas still moves in the form of a microchannel, but the airflow channel is relatively dispersed and curved, while in the non-uniform medium, The gas is mainly a trough flow and appears as a block region. Based on the experimental conditions in laboratory, the physical model is constructed. Based on the transformation of Darcy's law and Bessel's function theory, the Fredlund and Xingfx models in the soil and water characteristic curves are combined with the van Genuchtene VG model. In this paper, an as axisymmetric air flow model under the condition of two-dimensional sand tank experiment is proposed, and the model is verified by laboratory as experiment.
【學位授予單位】：吉林大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：X523

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