【作者】 李永涛；

【导师】 王文科；

【作者基本信息】 长安大学 ， 地质工程， 2010， 博士

【摘要】 轻非水相液体(LNAPLs)属典型的有机污染物,其泄漏后进入包气带,对土壤及地下水污染严重,已成为当前地下水环境保护中的核心课题。本文以多孔介质流体动力学、溶质运移动力学和水文地质学理论为指导,以柴油作为代表污染质,从物理模拟试验入手,模拟LNAPLs在包气带的污染行为,重点研究LNAPLs在包气带中的运移规律,并从三相流角度建立了LNAPLs在包气带运移的多相流数学模型,定性定量研究LNAPLs在包气带中运移问题,揭示了LNAPLs在包气带中的运移机理,主要研究成果如下：1)利用自制物理模拟试验装置,开展了LNAPLs在不同介质中的油水驱替试验,揭示了LNAPLs在包气带中的运移规律及特征。得出LNAPLs在渗漏初期主要受重力作用驱动,锋面尚未到达地下水毛细区上边缘时,其运动以垂向迁移为主,并保持规则的、圆弧形移动,当锋面到达毛细区上边缘以后,柴油沿着毛细区上边缘横向扩展,垂向进入毛细区和地下水中的部分有限；在不同介质中油流锋面具有不同分布特征,即均质介质油流锋面可分为残余油区及毛细带聚集油区,上细下粗型介质为聚集区-残余油区-聚集油区组合形式,含夹层型介质为残余油区及聚集油区交替出现型；影响油流锋面分布特征的因素主要有包气带岩性、初始水相压力、流场变化等；锋面最大发育宽度受孔隙度及介质渗透性能限制,当存在弱渗透性介质时,锋面横向发育加大尤为明显,反映出弱渗透性介质对污染物的阻滞作用,上述规律为揭示机理奠定基础。2)利用砂性漏斗试验装置所获取的两相系统各流体对之间的s-p关系,并借助F.F.Fagerlund折算理论将两相系统k-s-p关系扩展到三相系统,系统研究了三相系统中k-s-p关系。三相系统中,油、水两相的k-s曲线形状均为上凹型,各相相对渗透率曲线变化在小于等渗点饱和度之前,水相相对渗透率增加较慢而油相气相相对渗透率减小较快,当大于等渗点饱和度后,水相相对渗透率增加较快而油相缓慢减少至零。上述研究为分析多相流动以及对多相流问题进行数学模拟奠定基础。3)借助油气藏渗流力学理论,从多相流角度出发构建了描述LNAPLs在包气带运移的多相流动力学模型,并运用TOUGH2软件求解模型,反演后参数与实测参数基本吻合,为LNAPLs的污染预测及机理分析提供了定量支撑。4)基于物理模拟试验及数学模型,定性定量研究了LNAPLs在包气带中的迁移机理。得出在一定渗漏量下,均质介质颗粒越粗,LNAPLs越易到达毛细带。而进入毛细带中则以横向迁移为主,其中粗粒相横向迁移面积大于细粒相迁移面积,但在细粒相中LNAPLs聚集区的饱和度大于粗粒相。不论哪种砂性介质,油相发生横向迁移时水相饱和度为0.45。对于以砂性介质为主的非均质结构地层,弱渗透性介质存在对油相下移尽管有一定阻滞作用,但对于长期泄漏源,弱渗透夹层存在不足以完全阻滞油相下移,故应该重视输油管道泄漏等问题。本文研究对于定量化研究有机污染物在地下环境系统中迁移、污染预测提供理论依据和试验支持,对于确保地下水资源的可持续利用以及有效控制及修复LNAPLs污染具有一定的理论价值和实际意义。更多还原

【Abstract】 Light non-aqueous phase pollutant (LNAPLs) is the typical organic compounds, can cause serious soil and groundwater pollution after spilled into vadose zone,the issue of organic pollution has become the core topic of groundwater environment protection.Therefore, under the guidance of the porous medium hydrodynamics solute migration dynamics and the hydrogeology theory, the paper make the diesel oil represents LNAPLs, simulated the pollution behavior of two-dimensional region through the laboratory physical model test, with emphasis on the disciplinarian in vadose zone, and also established the migration multi-phase flow mathematical model of LNAPLs in vadose zone from the perspective of three-phase flow, revealed the the migration mechanism and the influencing factor qualitatively and quantitatively. the main research results are as follows:(1)The displacement experiments between oil-water has carried out in different media by self-physical simulation test device,and revealed migration laws and distribution characteristics of LNAPLs in the vadose zone. The results indicated that diesel oil transfer dominated by the vertical pattern at the initial stage of diesel leakage beause of the gravity controlling by the medium porosity and permeability, the frontal area maintains the rule, the round arc migration before the front on the edge of the capillary. After the front reached the edge of the capillary zone, the degree of front development grows slowly, diesel oil transport with the horizontal expansion and always along the edge of the capillary zone, vertically enters in the capillarity area and the ground water part is very limited. The oil frontal have different distribution characteristics in different media, the oil frontal can be divided into residual oil zone and capillary band together oil in homogeneous medium,and in thin coarse-type medium shows combination of gathered-residual-gathered oil zone,in containing sandwich-type medium shows residual-gathered oil zone alternating type.The characteristic of oil stream frontal concerned with the lithological character, initial aqueous phase pressure, flow field changes. The maximum growth width of frontal area confined by the porosity and the medium penetrating capability, The frontal area crosswise growth enlarges when has weak infiltration medium, it reflected the weak permeable medium has the obvious retardarce to the pollutant retardation.The laws lay the foundation to reveal the mechanism.(2) The relationship between s-p in two-phase system has obtained by sandy funnel test devices, and extended it into three-phase system using conversion theory of F. F. Fagerlund, studied the relationship of k-s-p in three-phase systemly.The results shows the k-s curve shape of oil and water is on concave no matter with which kind of lithological, the aqueous phase relative permeability increases slowly but the oil phase and gas phase relative permeability reduces quickly before the isotonia spot. After being bigger than an isotonia spot degree of saturation, the aqueous phase relative permeability increases but the oil phase reduces the to zero slowly.The results lay the foundation for analysis of multiphase flow and the mathematical simulation.(3) The multiphase flow dynamics model describing LNAPLs in vadose zone migtration was established from the perspective of multi-phase flow, and solve the model using TOUGH2 software, the inversion parameters are basically consistent with the measured parameters,it can provide quantitative support for forecast and analysis mechanism of LNAPLs pollution.(4) Based on physics-simulation and mathematical models, has studied migration mechanism of the LNAPLs in the vadose zone qualitatively and quantitatively.The results shows that the controlling factors of LNAPLs migration in the vadose zone are lithology, structure, and initial soil moisture content.Under a certain amount of leakage in homogeneous media,LNAPLs can reach the capillary zone. easily concerned with the media thickness level. The coarse granular media mains horizontal expansion after the front reached the capillary zone and transverse area in coarse-grained phase is larger than in the fine-grained phase, but the LNAPLs saturation of gathering zone in fine-grained phase is larger than in coarse-grained phase.Lateral migration of oil phase occurred when the water phas saturation threshold of 0.45 regardless of what kind of medium.For the hydrophilic medium, when the water phase occupies more than 45% pore space, LNAPLs migration blocked by water phase, the migration of LNAPLs show horizontal development.In non-homogeneous structure of strata.of sand-based medium,the weak penetration medium shows a certain blocking effect,but for long-term leakage source, it is not sufficient to completely block the downward movement of LNAPLs.Therefore, we should attach importance to pipeline leaks and other issues.The research can provides the theory basis and the experimental support for the quantitative research of migration, pollution forecast and prevention of organic pollutant in underground environment system, also have some theoretical value and practical significance for ensuring the sustainable use of groundwater resources and pollution control effectively.更多还原