考虑相变与滞后效应的汽油在非饱和土中运移规律研究

发布时间：2018-03-24 13:00

本文选题：非饱和土　切入点：汽油　出处：《北京交通大学》2017年硕士论文

【摘要】：现代城市建设过程中,地铁隧道开挖导致的加油站油库及输油管线泄露、石油开采以及城市污染企业厂址外迁而引发的土壤污染等工程问题,均涉及到含油气有机污染物在土中的迁移问题。因此,研究汽油等有机污染物在非饱和土中的运移分布规律、分析其影响因素十分必要,将为相关工程的安全建设运营以及污染治理提供理论基础和技术支持。本文首先基于多孔介质污染物迁移理论,从系统的平衡方程出发,重点考虑土中泄露汽油相变作用和液相滞后效应的影响,建立了描述非饱和土中NAPL-水-气运移规律的理论模型。随后,自主研制了能够模拟汽油在土层中运移的土柱实验装置,对汽油液、气两相在不同干密度、含水率条件下非饱和土中的运移规律开展了实验研究。最后,基于建立的模型,采用数值方法模拟了汽油在非饱和土中运移过程,研究了液、气两相汽油在土层中的运移分布规律,重点分析了滞后效应对汽油运移分布的影响,并对干密度和含水量等土体参数进行了敏感性分析。主要研究成果包括:(1)基于多孔介质污染物迁移理论,重点考虑土中非水相流体(NAPL)的相变和液相滞后效应的影响,建立了非饱和土中NAPL-水-气运移模型。针对非饱和土以及NAPL的特点,分析了影响非饱和土中NAPL运移的主要因素;建立了非饱和土中NAPL运移质量平衡方程,并对流体物性参数、动力弥撒系数以及相变速率和流体流动特性进行了描述;以VG模型为基础,建立了考虑滞后效应的两相和三相流K-S-P本构模型。(2)研制了非饱和土中汽油运移土柱实验装置,通过开展土柱实验研究,揭示了不同相态汽油在非饱和土中的运移及分布规律。研制了一种能够模拟汽油运移的土柱实验装置,提出了不同状态非饱和土中不同相态汽油迁移分布的测定方法;基于该装置,针对北京有轨电车西郊线植物园站-万安公墓站区间下穿香泉环岛隧道工程中的加油站油库泄漏问题,对取自该工程现场的土样开展了不同干密度和含水量土样的汽油渗透土柱实验研究,揭示了液相和气相汽油在非饱和土中的运移及分布规律,实验结果表明,增大含水率或减小干密度均会加速汽油的运移。(3)基于土柱实验成果,采用已建立的数学模型,利用数值模拟的手段,通过建模计算分析了汽油泄漏后在非饱和土中的运移分布规律。基于所建立的数学模型及实验研究成果,利用NAPL Simulator完善了考虑相变和滞后的非饱和土中NAPL运移计算程序和模拟方法;建立了一维土柱计算模型并开展计算,通过与土柱实验结果的对比验证了所建立理论模型及程序的合理性;建立了二维数值模型,通过数值计算给出了液相和气相汽油的空间分布特点、典型位置汽油浓度演化规律,并重点分析了滞后效应和干密度的影响。结果表明:汽油在土层中运移主要受重力和毛细压力作用,最终会在地下水位以上的毛细上升区大量聚集,并向水平方向扩展;气相浓度随深度增加而增大,直至在某一深度处达到平衡浓度;气相分布范围明显大于液相;滞后效应对于汽油的迁移有明显的阻滞作用。
[Abstract]:The process of modern city construction, oil and gas station pipeline leak caused by tunnel excavation, soil pollution and other engineering problems of oil exploitation and pollution of the city site relocation triggered by problems are related to the migration of oil and gas of organic pollutants in soil. Therefore, research on gasoline and other organic contaminant transport in unsaturated soils distribution, it is necessary to analyze the influencing factors, to provide theoretical basis and technical support for related engineering construction and operation safety and pollution control. Firstly, based on the theory of transfer of porous medium of pollutants, starting from the balance equation of the system, mainly considering the influence of soil leakage and liquid phase changing gasoline phase lag effect, was established to describe the non the theoretical model of NAPL- saturated water gas shift in soil. Then, the experimental device can independently developed a soil column simulated gasoline migration in soil, The liquid gasoline, gas phase in different dry density, migration in saturated soil to carry out experimental study on non moisture conditions. Finally, based on the established model, the numerical simulation of gasoline in unsaturated soils during the migration of liquid, gas, gasoline migration in soil distribution, key analysis of the lag effect on gasoline transport and distribution, and the dry density and water content of the soil parameter sensitivity analysis is carried out. The main results include: (1) based on the transfer theory of porous medium pollutants, focus on non water phase flow in soil (NAPL) effect of phase transition and liquid phase lag effect, set up in unsaturated soil NAPL- water migration model for unsaturated soils and the characteristics of NAPL, analyzes the main factors affecting NAPL migration in saturated soil is established; unsaturated soil mass balance equation of NAPL migration, and convection body Dynamic parameters, mass coefficient and phase velocity and fluid flow characteristics are described; based on VG model, established the K-S-P constitutive model considering the lag effect of two-phase and three-phase. (2) developed gasoline migration in unsaturated soil column experiment device, through the study of soil column experiment, migration and distribution law reveals a different phase of gasoline in unsaturated soils. Developed a soil column experiment device can simulate gas migration, put forward different state in different phase of gasoline in the saturated soil migration method for determining the distribution; based on the device, for the Beijing tram line west botanical garden station Wanan cemetery station through interval Xiangquan Island tunnel engineering in gas station oil leakage problem of the project site from soil samples carried out different dry density and water content of soil gas column experiment reveals the soil permeability, liquid and gas Gasoline is the law of movement and distribution in unsaturated soils, the experimental results show that the increase of migration rate of water or reduce dry density will accelerate gasoline. (3) based on the results of soil column experiments, the mathematical model has been established, using the method of numerical simulation, the modeling calculation and analysis of gasoline leak in in the saturated soil migration. The mathematical model and experimental study based on the results of using NAPL Simulator to improve the non program and the simulation method of calculating NAPL migration in saturated soil considering the transformation and lag; calculation model and carry out the calculation of one-dimensional soil column is established, verified the rationality of the model and program by compared with the experimental results of soil column; a two-dimensional numerical model, the spatial distribution characteristics of liquid phase and gas phase of gasoline are given by numerical calculation, the typical position of gasoline concentration evolution, and analyzes the The hysteresis effect and density. The results showed that the gasoline migration in soil is mainly affected by gravity and capillary pressure, will eventually rise above the water level in the capillary zone gathered, and extended to the horizontal direction; the gas concentration increases with the depth increasing, until at a certain depth to reach the equilibrium concentration of gas phase; the distribution range was significantly greater than the liquid phase; the lag effect has obvious retarding effect on gas migration.

【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X53

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