首页|孔隙特征对土体内部流动特性的影响——孔隙尺度的数值研究

孔隙特征对土体内部流动特性的影响——孔隙尺度的数值研究

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目的:研究土体内部的流动现象对岩土、农业及地质工程等领域具有重要意义.本文旨在探讨孔隙的平均直径、直径标准差、配位数及各向异性对土体内部水压、流量分布、流动模式及关键流动路径的影响,为评估土质屏障中的优势流动行为提供依据.创新点:1.在孔隙尺度分析孔隙特征对土体宏观渗透率及内部流动规律的影响;2.评估多个孔隙特征参数(如孔隙的平均直径、直径标准差、配位数及三种孔隙直径分布形式)对土体内部优势流动行为的影响.方法:1.将土体孔隙空间简化为由孔隙与吼道互相连接构成的球-杆模型,并通过改变孔隙和吼道的特征参数来描述复杂的孔隙结构;2.利用孔隙网络模型得到单元体内部水压和流量分布情况,为计算土体固有渗透率和评估其流动特性提供基础数据;3.基于击穿路径的概念,分析不同孔隙特征下土体内部流动的迂曲和非均匀程度;4.通过引入吼道收缩系数,调整水平或竖直吼道直径大小,评估孔隙各向异性对流动规律的影响.结论:1.土体的孔隙率和固有渗透率均随着孔隙直径平均值的增大、标准差的减小及配位数的增大而增大.2.孔隙直径的变异系数(COV)越高,土体内部水压和流量的分布越不均匀;配位数的提高会削弱水压的局部化分布但会提高流量的不均匀程度.3.随着COV的提高,击穿路径变得更加曲折;当COV由0增加到1.0时,击穿路径的迂曲度由1.00增加到大约1.71,击穿路径承担的流量占总流量的比值由2.0％提高到7.8％.4.水平与竖直吼道直径比值的提高,也会导致击穿路径迂曲度的提高;水平与竖直固有渗透率的比值和水平与竖直吼道直径的比值呈双对数线性相关.
A pore-scale numerical investigation of the effect of pore characteristics on flow properties in soils
Flow properties of soils can impact a wide range of geotechnical,agricultural,and geophysical processes.Few studies focus on the physical understanding of how pore characteristics can affect flow properties in soils.In this paper,pore network modeling is utilized to investigate intrinsic permeability,water pressure distributions,flow patterns,and critical flow paths in soils with pores varying in size,connectivity,and anisotropy.The results show that increased mean diameter,decreased standard deviation,and increased coordination number of the pores can lead to an increase in intrinsic permeability in soils.Non-uniform water pressure and flow rate distribution will more likely occur in soils with a larger pore size variability.A higher coordination number mitigates the pressure localization but slightly exacerbates non-uniform flow.With the increase in the coefficient of variation (COV) of pore diameters,the percolation path becomes more tortuous and carries more flow.When COV increases from 0 (homogeneous) to 1 (large pore size variability),the tortuosity increases from 1.00 to ～1.71 and the flux carried by the percolation path in soils increases from 2.0％ to 7.8％.Pronounced preferential flows may take place in soils with uniformly distributed pore sizes,in which the percolation path can carry as much as 9.2％ of the total flux.The anisotropy in pore throat sizes also increases the flow tortuosity and the fraction of flux carried by the percolation path.The permeability anisotropy Kh/Kv increases linearly as the pore throat size anisotropy μdh/μdv increases logarithmically.These results provide insight for designing soil barriers for either uniform flows or exacerbated preferential flow for fast transport.

Pore network modelingIntrinsic permeabilityFlow propertiesPore characteristics

Guang-yao LI、Sheng DAI、Liang-tong ZHAN、Yun-min CHEN

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MOE Key Laboratory of Soft Soils and Environmental Engineering, Zhejiang University, Hangzhou 310058, China

School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta 30332 GA, USA

孔隙网络模型 固有渗透率 流动特性 孔隙特征

Project supported by the National Science Fund for Distinguished Young ScholarsProject supported by the National Science Fund for Distinguished Young ScholarsProgram of China Scholarships CouncilZhejiang Provincial Key Research Project of ChinaEngineering Research Center Program of the US National Science Foundationand the US DOE/NETL Gas Hydrate Research Program

No.51625805ChinaNo.201706320096No.2015C03021No.EEC-1449501

2019

浙江大学学报(英文版)(A辑:应用物理和工程)
浙江大学

浙江大学学报(英文版)(A辑:应用物理和工程)

CSTPCDCSCDSCIEI
影响因子：0.556
ISSN：1673-565X
年,卷(期)：2019.20(12)
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