MODELING GROUNDWATER FLOW AND MASS TRANSPORT IN HETEROGENEOUS MEDIA: ISSUES AND CHALLENGES
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摘要: 对大空间尺度和长时间跨度的地下水流动及污染物质运移进行预测的需求, 使水文地质研究面临异乎寻常的挑战.这些需求来自于对核废料地质储放方法的安全性评价、地下水污染状况评价及其治理方案的选择.流动系统的非均质性是地下水流动及物质运移模拟中最主要的困难之一, 这种困难来自对非均质系统进行特征描述(通过原位观测实现)、概念化及模拟.评述了非均质介质中流动运移模拟的一些重要问题与挑战, 讨论了解决的途径.讨论的主题包括: 动力流动的沟道化, 示踪剂穿透曲线, 裂隙岩石中流体流动的多尺度, 观测的不同尺度, 模拟、预测与非均质性以及系统特征描述和预测性模拟的分析.Abstract: The need for predictions of groundwater flow and contaminant transport in the subsurface over large distances and long time periods has imposed extraordinary demands on the field of hydrogeology. Such a need arises in assessing the safety of a geologic nuclear waste repository and in evaluating groundwater contamination and remediation designs. One of the main difficulties in modeling groundwater flow and mass transport is the heterogeneity of the flow system, both in terms of its characterization through in situ measurements and its conceptualization and simulation. The paper reviews some important issues and challenges in modeling flow and transport in heterogeneous media, and discusses approaches to address certain aspects of the problem. Topics discussed include dynamic flow channeling, tracer breakthrough curves, multiple scales for flow in fractured rocks, different scales in measurement, modeling, prediction and heterogeneity, and system characterization and analysis for predictive modeling.
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Key words:
- groundwater /
- contamination /
- modeling /
- heterogeneous media /
- multiple scales
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图 1 二维非均质介质中流动沟道化随σ的变化
Fig. 1. Emergence of flow channeling, under pressure step applied from the top to the bottom boundary, as a function of σ for a 2D heterogeneous medium
a.λ′=0.15, σ=0.5;b.λ′=0.15, σ=2.0;c.λ′=0.15, σ=6.0
图 2 二维非均质介质中流动沟道化随λ′的变化
Fig. 2. Emergence of flow channeling, under pressure step applied from the top to the bottom boundary, as a function of λ′ for a 2D heterogeneous medium
a.λ′=0.015, σ=2.0;b.λ′=0.15, σ=2.0;c.λ′=0.3, σ=2.0
图 5 隙宽变化的裂隙网络中示踪剂穿透曲线(裂隙间距在4~8 m范围变化)
Fig. 5. Tracer breakthrough curves for a fracture network with variable apertures for each fracture
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