基于多相流模型和探地雷达正演模拟的LNAPLs探测研究
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摘要
探地雷达(Ground Penetrating Radar:GPR)不仅可以用于估计土壤含水量,还可以用于探测和监测轻非水相液体(Light Non Aqueous Phase Liquids:LNAPLs)在土壤中的运移.建立接近实际情况的模型是利用GPR正演模拟开展LANPLs迁移和分布研究的关键问题.以往的地球物理模型大都属于概念模型,存在物性突变的界面.而在LNAPLs污染区域的各种物性参数通常是渐变的,大多数情况下并不存在突变的物性界面.因此,为了建立更符合实际的地球物理模型,本文基于多相流渗流理论模拟了LNAPLs在土壤中的泄漏过程,得到了渗漏后不同时刻土壤含水饱和度、含油饱和度的变化分布.然后利用混合介质的介电模型将流体饱和度分布转换为介电常数分布,获得了地球物理模型,显示了因LNAPLs迁移引起的土壤介电常数的细节变化.随后,基于时域有限差分开展了GPR正演模拟.正演模拟结果显示了雷达波对LNAPLs污染区域、潜水面的响应,与实验室实测数据具有很好的一致性.由以上分析、对比可知,本文提出的地球物理建模的方法和流程与污染场地的实际情况更为符合.基于多相流渗流理论建立的地球物理正演模型把地下LNAPLs迁移的水文模型与GPR探测相结合,为复杂的实际场地地球物理建模提供了思路,也为GPR更有效地探测LNAPLs在土壤中的渗流提供了分析和解释手段.
Ground Penetrating Radar(GPR) can be applied not only for estimating soil moisture but also for detecting and monitoring the migration of Light Non Aqueous Phase Liquids(LNAPLs) in soils. It is a key issue to establish a model close to the actual situation in the GPR forward simulation to study the LNAPLs migration in soils. Most of the geophysical models currently used for LNAPLs soil contamination can be considered as conceptual models with a sudden change of physical properties in interface. However, the the physical parameters usually change gradually in the LNAPLs contaminated area, and the sudden-change interfaces in physical properties usually do not exsit. In order to establish a more realistic geophysical model, this paper simulates the leakage process of LNAPLs in soil based on a multiphase flow theory, and obtains the distribution of water saturation and oil saturation at different times after leakage in soils. Then, a geophysical model is obtained by using the dielectric model of the mixed media to convert the fluid saturation distribution into a dielectric constant distribution. The obtained geophysical model shows the dielectric constant change caused by the migration of LNAPLs in detail. After that, the GPR forward modeling is carried out with the obtained model using the Finite Difference in Time Domain(FDTD) method. The results show the responses of the radar wave to the LNAPLs contaminated area and the water table, which correspond to the actual measured data in the laboratory. From the above analysis and comparison, the method and flow for establishing a geophysical model proposed in this paper are more consistent with the actual situation of the contaminated site. The geophysical forward model based on the multiphase flow theory combines the hydrological model with GPR detection, and provides ideas for geophysical modeling of complex sites, and it is a tool of analysis and interpretation for the GPR detection of LNAPLs.
Ground Penetrating Radar(GPR) can be applied not only for estimating soil moisture but also for detecting and monitoring the migration of Light Non Aqueous Phase Liquids(LNAPLs) in soils. It is a key issue to establish a model close to the actual situation in the GPR forward simulation to study the LNAPLs migration in soils. Most of the geophysical models currently used for LNAPLs soil contamination can be considered as conceptual models with a sudden change of physical properties in interface. However, the the physical parameters usually change gradually in the LNAPLs contaminated area, and the sudden-change interfaces in physical properties usually do not exsit. In order to establish a more realistic geophysical model, this paper simulates the leakage process of LNAPLs in soil based on a multiphase flow theory, and obtains the distribution of water saturation and oil saturation at different times after leakage in soils. Then, a geophysical model is obtained by using the dielectric model of the mixed media to convert the fluid saturation distribution into a dielectric constant distribution. The obtained geophysical model shows the dielectric constant change caused by the migration of LNAPLs in detail. After that, the GPR forward modeling is carried out with the obtained model using the Finite Difference in Time Domain(FDTD) method. The results show the responses of the radar wave to the LNAPLs contaminated area and the water table, which correspond to the actual measured data in the laboratory. From the above analysis and comparison, the method and flow for establishing a geophysical model proposed in this paper are more consistent with the actual situation of the contaminated site. The geophysical forward model based on the multiphase flow theory combines the hydrological model with GPR detection, and provides ideas for geophysical modeling of complex sites, and it is a tool of analysis and interpretation for the GPR detection of LNAPLs.
引文
Abdel Aal G Z,Slater L D,Atekwana E A. 2006. Induced-polarization measurements on unconsolidated sediments from a site of active hydrocarbon biodegradation [J]. Geophysics. 71(2): H13-H24,doi: 10.1190/1.2187760.
Bano M,Loeffler O,Girard J F,et al. 2009. Ground penetrating radar imaging and time-domain modelling of the infiltration of diesel fuel in a sandbox experiment [J]. Comptes rendus Geoscience,341(10-11): 846-858.
Bertolla L,Porsani J L,Soldovieri F,et al. 2014. GPR- 4D monitoring a controlled LNAPL spill in a masonry tank at USP,Brazil [J]. Journal of Applied Geophysics,103(4): 237-244.
Birchak J R,Gardner C G,Hipp J E,et al. 1974. High dielectric constant microwave probes for sensing soil moisture [J]. Proceedings of the IEEE,62(1): 93-98.
Catapano I,Affinito A,Bertolla L,et al. 2014. Oil spill monitoring via microwave tomography enhanced GPR surveys [J]. Journal of Applied Geophysics,108(9): 95-103.
Glaser D R,Werkema D D,Versteeg R J,et al. 2012. Temporal GPR imaging of an ethanol release within a laboratory-scaled sand tank [J]. Journal of Applied Geophysics,86(8): 133-145.
Irving James,Knight R. 2006. Numerical modeling of ground-penetrating radar in 2-D using MATLAB ☆ [J]. Computers & Geosciences,32(9): 1247-1258.
Lago A L,Elis V R,Borges W R,et al. 2009. Geophysical investigation using resistivity and GPR methods: a case study of a lubricant oil waste disposal area in the city of Ribeir?o Preto,S?o Paulo,Brazil [J]. Environmental Geology,58(2): 407- 417.
Li H L,Lu Q,Feng X,et al. 2012. Experimental Study on Dielectric Properties of LNAPL Contaminated Soil——Taking Quartz Sand as an Example [J]. Global Geology (in Chinese),31(2): 426- 432.李洪丽,鹿琪,冯晅,等. 2012. LNAPL污染土壤介电性质的实验研究——以石英砂为例[J]. 世界地质,31(2): 426- 432.
Li Y. 2014. Algorithm research and numerical simulation of LNAPLs migration in aerated zone [Master’s thesis]. Jilin University.李晔. 2014. LNAPLs在包气带中运移的算法研究及其数值模拟[硕士论文]. 吉林大学.
Li Y T. 2010. Migration Mechanism and Simulation of LNAPLs in Vadose Zone [Ph.D. thesis]. Chang’an University.李永涛. 2010. LNAPLs在包气带中运移机理及模拟研究[博士论文]. 长安大学.
Liu H L,Zhang S. 2014. High Density Resistivity Imaging Monitoring of LNAPL Contamination Process in Heterogeneous Porous Media [J]. Progress in Geophysics (in Chinese),29(05): 2401-2406,doi: 10.6038/pg20140561.刘汉乐,张闪. 2014. 非均质多孔介质中LNAPL污染过程的高密度电阻率成像法监测[J]. 地球物理学进展,29(05): 2401-2406,doi: 10.6038/pg20140561.
Loor G P D. 1968. Dielectric Properties of Heterogeneous Mixtures Containing Water [J]. Journal of Microwave Power,3(2): 67-73.
Mayer A S,Miller C T. 1996. The influence of mass transfer characteristics and porous media heterogeneity on nonaqueous phase dissolution [J]. Water Resources Research,32(6): 1551-1567.
Olhoeft G R. 1992. Geophysical Detection of Hydrocarbon and Organic Chemical Contamination [C] Symposium on the Application of Geophysics to Engineering and Environmental Problems Environment and Engineering Geophysical Society,1992:663.
Pettersson J K,Nobes D C. 2003. Environmental geophysics at Scott Base: ground penetrating radar and electromagnetic induction as tools for mapping contaminated ground at Antarctic research bases [J]. Cold Regions Science & Technology,37(2): 187-195.
Schwille F. 1967. Petroleum contamination of the subsoil-a hydrological problem. In: P. Hepple(Editor),The Joint Problems of the Oil and Water Industries[J]. Elsevier,Amsterdam,23-53.
Topp G C,Davis J L,Annan A P. 1980. Electromagnetic determination of soil water content: measurements in coaxial transmission lines [J]. Water Resources Research,16(3): 574-582.
Von Hippel,A.R. (Editor),1961. Dielectric Materials and Applications. MIT Press,Cambridge,MA,438 pp.
Wang C H. 2007. Ground Penetrating Radar Method for Measuring Near-surface Water Content and Pollutant Detection [Master’s thesis]. Jilin University.王春辉. 2007. 探地雷达方法测量近地表含水量及污染物探测研究[硕士论文]. 吉林大学.
Wang H T. 2008. Dynamics of fluid flow and contaminant transport in porous media [M]. Higher Education Press.王洪涛. 2008. 多孔介质污染物迁移动力学[M]. 高等教育出版社.
Wu Y Q. 2011. Mathematical model of seepage and contaminant migration in porous media [M]. Science Press.仵彦卿. 2011. 多孔介质渗流与污染物迁移数学模型[M]. 科学出版社.
Zhang W Z. 1996. Groundwater and Soil Hydrodynamics [M]. Beijing: China Water Resources and Hydropower Press,347-350.张蔚榛. 1996. 地下水与土壤水动力学[M]. 北京:中国水利水电出版社,347-350.
Zhang X R. 2007. Migration and transformation model of oil pollutants in seepage zone and its numerical simulation [Master’s thesis]. Jilin University.张学润. 2007. 渗流带中油类污染物的迁移转化模型及其数值模拟[硕士论文]. 吉林大学.
Bano M,Loeffler O,Girard J F,et al. 2009. Ground penetrating radar imaging and time-domain modelling of the infiltration of diesel fuel in a sandbox experiment [J]. Comptes rendus Geoscience,341(10-11): 846-858.
Bertolla L,Porsani J L,Soldovieri F,et al. 2014. GPR- 4D monitoring a controlled LNAPL spill in a masonry tank at USP,Brazil [J]. Journal of Applied Geophysics,103(4): 237-244.
Birchak J R,Gardner C G,Hipp J E,et al. 1974. High dielectric constant microwave probes for sensing soil moisture [J]. Proceedings of the IEEE,62(1): 93-98.
Catapano I,Affinito A,Bertolla L,et al. 2014. Oil spill monitoring via microwave tomography enhanced GPR surveys [J]. Journal of Applied Geophysics,108(9): 95-103.
Glaser D R,Werkema D D,Versteeg R J,et al. 2012. Temporal GPR imaging of an ethanol release within a laboratory-scaled sand tank [J]. Journal of Applied Geophysics,86(8): 133-145.
Irving James,Knight R. 2006. Numerical modeling of ground-penetrating radar in 2-D using MATLAB ☆ [J]. Computers & Geosciences,32(9): 1247-1258.
Lago A L,Elis V R,Borges W R,et al. 2009. Geophysical investigation using resistivity and GPR methods: a case study of a lubricant oil waste disposal area in the city of Ribeir?o Preto,S?o Paulo,Brazil [J]. Environmental Geology,58(2): 407- 417.
Li H L,Lu Q,Feng X,et al. 2012. Experimental Study on Dielectric Properties of LNAPL Contaminated Soil——Taking Quartz Sand as an Example [J]. Global Geology (in Chinese),31(2): 426- 432.李洪丽,鹿琪,冯晅,等. 2012. LNAPL污染土壤介电性质的实验研究——以石英砂为例[J]. 世界地质,31(2): 426- 432.
Li Y. 2014. Algorithm research and numerical simulation of LNAPLs migration in aerated zone [Master’s thesis]. Jilin University.李晔. 2014. LNAPLs在包气带中运移的算法研究及其数值模拟[硕士论文]. 吉林大学.
Li Y T. 2010. Migration Mechanism and Simulation of LNAPLs in Vadose Zone [Ph.D. thesis]. Chang’an University.李永涛. 2010. LNAPLs在包气带中运移机理及模拟研究[博士论文]. 长安大学.
Liu H L,Zhang S. 2014. High Density Resistivity Imaging Monitoring of LNAPL Contamination Process in Heterogeneous Porous Media [J]. Progress in Geophysics (in Chinese),29(05): 2401-2406,doi: 10.6038/pg20140561.刘汉乐,张闪. 2014. 非均质多孔介质中LNAPL污染过程的高密度电阻率成像法监测[J]. 地球物理学进展,29(05): 2401-2406,doi: 10.6038/pg20140561.
Loor G P D. 1968. Dielectric Properties of Heterogeneous Mixtures Containing Water [J]. Journal of Microwave Power,3(2): 67-73.
Mayer A S,Miller C T. 1996. The influence of mass transfer characteristics and porous media heterogeneity on nonaqueous phase dissolution [J]. Water Resources Research,32(6): 1551-1567.
Olhoeft G R. 1992. Geophysical Detection of Hydrocarbon and Organic Chemical Contamination [C] Symposium on the Application of Geophysics to Engineering and Environmental Problems Environment and Engineering Geophysical Society,1992:663.
Pettersson J K,Nobes D C. 2003. Environmental geophysics at Scott Base: ground penetrating radar and electromagnetic induction as tools for mapping contaminated ground at Antarctic research bases [J]. Cold Regions Science & Technology,37(2): 187-195.
Schwille F. 1967. Petroleum contamination of the subsoil-a hydrological problem. In: P. Hepple(Editor),The Joint Problems of the Oil and Water Industries[J]. Elsevier,Amsterdam,23-53.
Topp G C,Davis J L,Annan A P. 1980. Electromagnetic determination of soil water content: measurements in coaxial transmission lines [J]. Water Resources Research,16(3): 574-582.
Von Hippel,A.R. (Editor),1961. Dielectric Materials and Applications. MIT Press,Cambridge,MA,438 pp.
Wang C H. 2007. Ground Penetrating Radar Method for Measuring Near-surface Water Content and Pollutant Detection [Master’s thesis]. Jilin University.王春辉. 2007. 探地雷达方法测量近地表含水量及污染物探测研究[硕士论文]. 吉林大学.
Wang H T. 2008. Dynamics of fluid flow and contaminant transport in porous media [M]. Higher Education Press.王洪涛. 2008. 多孔介质污染物迁移动力学[M]. 高等教育出版社.
Wu Y Q. 2011. Mathematical model of seepage and contaminant migration in porous media [M]. Science Press.仵彦卿. 2011. 多孔介质渗流与污染物迁移数学模型[M]. 科学出版社.
Zhang W Z. 1996. Groundwater and Soil Hydrodynamics [M]. Beijing: China Water Resources and Hydropower Press,347-350.张蔚榛. 1996. 地下水与土壤水动力学[M]. 北京:中国水利水电出版社,347-350.
Zhang X R. 2007. Migration and transformation model of oil pollutants in seepage zone and its numerical simulation [Master’s thesis]. Jilin University.张学润. 2007. 渗流带中油类污染物的迁移转化模型及其数值模拟[硕士论文]. 吉林大学.