断层对地下水渗流场特征影响的数值模拟
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摘要
断层的存在影响着地下流场的运移和分布。该文建立了一个理想地区的地下含水系统模型,应用Modflow软件,考虑断层倾向、走向、渗透系数等因素的影响,采用数值模拟方法研究并探讨了断层对模拟区渗流场水头分布的影响特征。研究结果表明:①倾向不同的断层,以垂直断层对流场水头值的影响最为显著;②不同走向断层对流场的影响,主要受断层走向与流线夹角的控制,夹角越大,对流场的影响越显著;③断层的导水性质对模拟区流场水头值分布的影响较大,断层表现为导水或阻水性质,主要取决于断层渗透率与周围介质渗透率的关系;④断层附近的流场梯度变化较大,距离断层越近,流场受断层的影响就越明显,随着离断层距离的增大,影响效应逐步减弱。这项研究结果有助于深入认识断层对地下流体动态的影响,以及对地震前兆特征的解释。
The transportation and distribution of groundwater are affected by the existence of faults. In this article, by applying Visual Modflow, and modeling environment for practical applications in three-dimensional groundwater flow, we build the mathematical model of a conceptual region's groundwater system and research the groundwater seepage under the influence of faults with different dips, strikes and permeability. According to the results made by the identification and analysis with the model, we draw the conclusions as follows: ① Faults with different dips have a different role on the flow field, among the faults with same strikes and other characteristics, vertical fault is the most significant one. ② The impacts of faults on the entire region flow field of faults depend on the angles between the strike and the flow lines of the entire region flow field. The bigger the angle is, the more significant the impact is. ③ Different permeability is also an important factor that affects the distribution of the region flow field. Whatever the fault is considered as a conduit or a barrier, it depends on the differences of the conductivities between fault and protolith. ④ The distance from the fault is also one of the factors that affects the trends of water wells. The closer the distance is, the more obvious the change of water level is. As the distance becomes farther, the impact is not significant. This study will help us to further understand the dynamic effect interaction between fault activity and the migration of underground fluid, and also help us to deepen understanding of the mechanism of precursors during the process of earthquake generation.
The transportation and distribution of groundwater are affected by the existence of faults. In this article, by applying Visual Modflow, and modeling environment for practical applications in three-dimensional groundwater flow, we build the mathematical model of a conceptual region's groundwater system and research the groundwater seepage under the influence of faults with different dips, strikes and permeability. According to the results made by the identification and analysis with the model, we draw the conclusions as follows: ① Faults with different dips have a different role on the flow field, among the faults with same strikes and other characteristics, vertical fault is the most significant one. ② The impacts of faults on the entire region flow field of faults depend on the angles between the strike and the flow lines of the entire region flow field. The bigger the angle is, the more significant the impact is. ③ Different permeability is also an important factor that affects the distribution of the region flow field. Whatever the fault is considered as a conduit or a barrier, it depends on the differences of the conductivities between fault and protolith. ④ The distance from the fault is also one of the factors that affects the trends of water wells. The closer the distance is, the more obvious the change of water level is. As the distance becomes farther, the impact is not significant. This study will help us to further understand the dynamic effect interaction between fault activity and the migration of underground fluid, and also help us to deepen understanding of the mechanism of precursors during the process of earthquake generation.
引文
[1]南京大学地球科学系郭卫星,卢国平编译,MODFLOW三维有限差分地下水流模型,1998年.
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[11]Agust Gudmundsson.Active fault zones and groundwater[J].Geophysical Research Letters,2000,27(18):2993-2996.
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[14]李云峰.供水水文地质计算[M].北京:地质出版社,2007.
[15]薛禹群,朱学愚,吴吉春,等.地下水动力学[M].北京:地质出版社,1997.
[16]孙小龙,刘耀炜.应力加载作用引起地下水微温度场变化的研究综述[J].国际地震动态,2006,(7):17-26.
[1]Lizet B Christiansen,Shaul Hurwitz,Steven E Ingebritsen.Annual modulation of seismicity along the San Andreas Fault near Parkfield,CA[J].Geophysical Research Letters,2007,34:
[2]刘耀炜,陆斌.台湾车笼埔断层深井钻探计划(TCDP)概述[J].国际地震动态,2006,(2):14-20.
[3]Muir-Wood R,King G.Hydrological signatures associated with earthquake strain[J].Journal of Geophysical Research,1993,98:22035-22068.
[4]易立新,刘香,侯建伟,等.地震研究中的断层流体动力学问题[J].地震,2007,27(1):1-8.
[5]黄辅琼,陈颙,白长清,等.八宝山断层的变形行为与降雨及地下水的关系[J].地震学报,2007,27(6):637-646.
[6]Jonathan Saul Caine,James P Evans,Craig B Forster.Fault zone architecture and permeability structure[J].Geology,1996,24(11):1-8.
[7]David Wiprut,Mark D Zoback.Fault reactivation and fluid flowalong a preciously dormant normal fault in the northern North Sea[J].Geology,2000,28(7):595-598.
[8]Teruo Yamashita.Si mulation of seismicity due to fluid migrationin a fault zone[J].Geophys J Int,1998,132:674-686.
[9]Manzocchi T,Walsh J J,Nell P.Fault transmissibility multipliers for flow si mulation models[J].Petroleum Geoscience,1999,5:53-63.
[10]Moretti I,Labaume P,Sheppard S.Compart mentalisation of fluid flowby thrust faults,Sub-Ande-an Zone,Bolivia[J].Journal of Geochemical Exploration,2000,(69-70):493-497.
[11]Agust Gudmundsson.Active fault zones and groundwater[J].Geophysical Research Letters,2000,27(18):2993-2996.
[12]车用太,鱼金子.地震地下流体学[M].北京:气象出版社,2006.
[13]李玉柱,苑明顺.流体力学[M].北京:高等教育出版社,1998.
[14]李云峰.供水水文地质计算[M].北京:地质出版社,2007.
[15]薛禹群,朱学愚,吴吉春,等.地下水动力学[M].北京:地质出版社,1997.
[16]孙小龙,刘耀炜.应力加载作用引起地下水微温度场变化的研究综述[J].国际地震动态,2006,(7):17-26.
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