Influences of geometric characteristics of intersecting fractures in rock mass on solute transport
-
摘要: 交叉裂隙溶质运移特征是岩体裂隙网络溶质运移的基础。对流与水动力弥散是非反应性溶质运移的主要控制机制,佩克莱数被用来评估两者在非反应性溶质运移过程中的占比影响。通过改变注入流体的流速,改变交叉裂隙的粗糙度、交叉角、开度比等几何特征,采用有限元数值分析获得了佩克莱数与交叉裂隙几何特征对溶质运移特性的影响规律。研究表明:随流体流速增大,溶质运移由弥散主导转向对流主导,实际工程中全面考虑弥散效应有助于准确评估交叉处溶质的混合程度;粗糙度仅影响溶质到达出口处的运移时间;交叉角、开度比通过影响溶质分子扩散到不同出口分支的概率、优势流的流动路径,显著改变了交叉处溶质的混合程度;不同流量比通过影响交叉处流向出口分支的优势流位置,影响了交叉处溶质的混合。研究结论可为油气地下储存、垃圾填埋、核废料处置等地下工程中地下水污染物的防控治理提供理论依据。Abstract: The solute transport characteristics of intersecting fracture are the basis of solute transport in fractured rock mass. The advection and hydrodynamic dispersion are the main controlling mechanisms of non-reactive solute transport, and the Péclet number is used to evaluate their proportions in the process of non-reactive solute transport. By changing the flow velocity of the injected fluid and the geometric characteristics of the intersecting fracture such as roughness, intersecting angle and aperture ratio, the influences of the Péclet number and geometric characteristics of intersecting fracture on solute transport characteristics are obtained through the finite element numerical analysis. The results show that with the increase of the fluid flow velocity, the solute transport changes from dispersion-dominated to advection-dominated. By comprehensively considering the dispersion effects in practical engineering, it is helpful to accurately evaluate the mixing degree of solute at the intersection. The roughness primarily affects the solute migration time towards outlets. The intersecting angle and aperture ratio significantly alter the mixing degree of solute at the intersections by affecting the probability of solute molecules diffusing to different outlet branches and the flow path of the dominant flow. Different flow ratios also affect the mixing of solutes at the intersection by influencing the positions of the dominant flow towards the outlet branches. The research conclusions can provide a theoretical basis for the prevention and control of groundwater pollutants in underground engineering such as oil and gas underground storage, landfill and nuclear waste disposal.
-
Keywords:
- intersecting fracture /
- solute transport /
- Péclet number /
- hydrodynamic dispersion
-
-
表 1 计算参数
Table 1 Computational parameters
参数 取值 流体密度ρ/(kg·m-3) 9.997×102 动力黏性系数μ(Pa·s) 1.307×10-3 分子扩散系数Dm/(m2·s-1) 2.03×10-9 纵向弥散度αL/m 1×10-6 表 2 模型变量表
Table 2 Model variables
变量符号 物理意义 下标取值 单位 qi 第i分支流体流量 i = 1,2,3,4 m3/s ci 第i分支溶质浓度 i = 1,2,3,4 mol/m3 vi 第i分支平均流速 i = 1,2,3,4 m/s ei 第i分支平均开度 i = 1,2,3,4 mm li 第i分支长度 i = 1,2,3,4 mm 表 3 工况设置
Table 3 Setting of working conditions
工况组 粗糙度JRC 交叉角θ1, 4/(°) 开度/mm e1 e2 Pe数 光滑 90 0.1 0.1 粗糙度 光滑,3.9
5.2,8.1
10.5,13.1
14.7,18.890 0.1 0.1 交叉角 光滑 5k,1≤k≤35且k∈Z 0.1 0.1 开度比 光滑 90 0.1 1 0.1 0.5 0.2 0.5 0.1 0.2 0.4 0.5 0.1 0.1 0.2 0.1 0.5 0.2 0.6 0.2 0.5 0.1 1 0.1 -
[1] 周志芳, 王锦国. 裂隙介质水动力学[M]. 北京: 中国水利水电出版社, 2004. ZHOU Zhifang, WANG Jinguo. Dynamics of Fluids in Fractured Media[M]. Beijing: China Water & Power Press, 2004. (in Chinese)
[2] 周新, 盛建龙, 叶祖洋, 等. 岩体粗糙裂隙几何特征对其Forchheimer型渗流特性的影响[J]. 岩土工程学报, 2021, 43(11): 2075-2083. ZHOU Xin, SHENG Jianlong, YE Zuyang, et al. Effects of geometrical feature on Forchheimer- flow behavior through rough-walled rock fractures[J]. Chinese Journal of Geotechnical Engineering, 2021, 43(11): 2075-2083. (in Chinese)
[3] 李博, 黄嘉伦, 钟振, 等. 三维交叉裂隙渗流传质特性数值模拟[J]. 岩土力学, 2019, 40(9): 3670-3678. LI Bo, HUANG Jialun, ZHONG Zhen, et al. Numerical simulation on hydraulic and solute transport properties of 3D crossed fractures[J]. Rock and Soil Mechanics, 2019, 40(9): 3670-3678. (in Chinese)
[4] LI B, MO Y Y, ZOU L C, et al. Influence of surface roughness on fluid flow and solute transport through 3D crossed rock fractures[J]. Journal of Hydrology, 2020, 582: 124284. doi: 10.1016/j.jhydrol.2019.124284
[5] BODIN J, DELAY F, DE MARSILY G. Solute transport in a single fracture with negligible matrix permeability: 1. fundamental mechanisms[J]. Hydrogeology Journal, 2003, 11(4): 418-433. doi: 10.1007/s10040-003-0268-2
[6] LI G M. Tracer mixing at fracture intersections[J]. Environmental Geology, 2002, 42(2): 137-144.
[7] ZOU L C, JING L R, CVETKOVIC V. Modeling of flow and mixing in 3D rough-walled rock fracture intersections[J]. Advances in Water Resources, 2017, 107: 1-9. doi: 10.1016/j.advwatres.2017.06.003
[8] WILSON C R, WITHERSPOON P A. Flow interference effects at fracture intersections[J]. Water Resources Research, 1976, 12(1): 102-104. doi: 10.1029/WR012i001p00102
[9] HULL L C, KOSLOW K N. Streamline routing through fracture junctions[J]. Water Resources Research, 1986, 22(12): 1731-1734. doi: 10.1029/WR022i012p01731
[10] HULL L C, MILLER J D, CLEMO T M. Laboratory and simulation studies of solute transport in fracture networks[J]. Water Resources Research, 1987, 23(8): 1505-1513. doi: 10.1029/WR023i008p01505
[11] JOHNSON J, BROWN S. Experimental mixing variability in intersecting natural fractures[J]. Geophysical Research Letters, 2001, 28(22): 4303-4306. doi: 10.1029/2001GL013446
[12] PHILIP J R. The fluid mechanics of fracture and other junctions[J]. Water Resources Research, 1988, 24(2): 239-246. doi: 10.1029/WR024i002p00239
[13] BERKOWITZ B, NAUMANN C, SMITH L. Mass transfer at fracture intersections: an evaluation of mixing models[J]. Water Resources Research, 1994, 30(6): 1765-1773. doi: 10.1029/94WR00432
[14] ROBINSON J W, GALE J E. A laboratory and numerical investigation of solute transport in discontinuous fracture systems[J]. Groundwater, 1990, 28(1): 25-36. doi: 10.1111/j.1745-6584.1990.tb02226.x
[15] STOCKMAN H W, JOHNSON J, BROWN S R. Mixing at fracture intersections: influence of channel geometry and the Reynolds and Peclet Numbers[J]. Geophysical Research Letters, 2001, 28(22): 4299-4302. doi: 10.1029/2001GL013287
[16] PARK Y J, LEE K K. Analytical solutions for solute transfer characteristics at continuous fracture junctions[J]. Water Resources Research, 1999, 35(5): 1531-1537. doi: 10.1029/1998WR900002
[17] WOLFSBERG A. Rock Fractures and Fluid Flow: Contemporary Understanding and Applications[M]. Washington D C: National Academy Press, 1996.
[18] JOHNSON J, BROWN S, STOCKMAN H. Fluid flow and mixing in rough-walled fracture intersections[J]. Journal of Geophysical Research: Solid Earth, 2006, 111(B12): B12206.
[19] 李崴, 王者超, 毕丽平, 等. 辐射流条件下裂隙岩体渗透性表征单元体尺寸与等效渗透系数[J]. 岩土力学, 2019, 40(2): 720-727. LI Wei, WANG Zhechao, BI Liping, et al. Representative elementary volume size for permeable property and equivalent permeability of fractured rock mass in radial flow configuration[J]. Rock and Soil Mechanics, 2019, 40(2): 720-727. (in Chinese)
[20] LIU J, WANG Z C, QIAO L P, et al. Nonlinear flow model for rock fracture intersections: the roles of the intersecting angle, aperture and fracture roughness[J]. Rock Mechanics and Rock Engineering, 2022, 55(4): 2385-2405. doi: 10.1007/s00603-022-02784-0
[21] 李传亮. 油藏工程原理[M]. 2版. 北京: 石油工业出版社, 2011. LI Chuanliang. Principle of Reservoir Engineering[M]. 2nd ed. Beijing: Petroleum Industry Press, 2011. (in Chinese)
[22] PEACOCK D C P, SANDERSON D J, ROTEVATN A. Relationships between fractures[J]. Journal of Structural Geology, 2018, 106: 41-53. doi: 10.1016/j.jsg.2017.11.010
[23] DIJK P, BERKOWITZ B. Precipitation and dissolution of reactive solutes in fractures[J]. Water Resources Research, 1998, 34(3): 457-470. doi: 10.1029/97WR03238
[24] 王志良, 申林方, 徐则民, 等. 岩体裂隙面粗糙度对其渗流特性的影响研究[J]. 岩土工程学报, 2016, 38(7): 1262-1268. WANG Zhiliang, SHEN Linfang, XU Zemin, et al. Influence of roughness of rock fractureon seepage characteristics[J]. Chinese Journal of Geotechnical Engineering, 2016, 38(7): 1262-1268. (in Chinese)
-
期刊类型引用(5)
1. 郭婷婷,刘建民,杨宏智. 土动剪切模量比的不确定性对莱州湾近海海域深软场地地震动参数的影响. 地球物理学进展. 2023(04): 1765-1774 . 百度学术
2. 王祥祺,王自法,赵登科,李兆焱. 基于KiK-net记录的PGA与Sa场地影响因子分布研究. 地震工程与工程振动. 2023(04): 204-215 . 百度学术
3. 邬俊杰,咸甘玲,刘娟,兰景岩. 基于有限差分法的非饱和砂土层地震反应研究. 洛阳理工学院学报(自然科学版). 2023(03): 17-21+25 . 百度学术
4. 艾志军. 磷石膏–水泥改良黄土动力特性试验. 岩土工程技术. 2021(05): 341-346 . 百度学术
5. 卢育霞,魏来,刘琨,李桐林,郑海忠,王常亚,杨博. 1920年海原地震滑坡密集区的地震动场地效应研究. 地震工程学报. 2020(05): 1151-1158 . 百度学术
其他类型引用(12)
-
其他相关附件