Laboratory investigations of effective flow behavior in unsaturated heterogeneous sands
Laboratory investigations of effective flow behavior in unsaturated heterogeneous sands
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DOI：
10.1029/98wr01958
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发表时间：
1999-01
影响因子：
5.4
通讯作者：
D. Wildenschild;K. Jensen
中科院分区：
文献类型：
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作者：
D. Wildenschild;K. Jensen
在受控的实验室条件下，研究了非均质砂土的二维非饱和流动和输运。采用稳态流量控制法测定了5种均质砂土及由其组成的3种非均质体系的非饱和导水率。非均质砂系统是在实验室水槽中建立的，用于三种实现均质砂的随机分布，包括207个网格单元的系统。在上边界处控制水通量，而在下边界处施加吸力，使得平均建立均匀的压力分布并施加重力流。在离散点在坦克使用时域反射仪，以及染料示踪剂的路径测量的溶质突破曲线，表明流动和运输发生在一个非常曲折的模式，其中几个网格单元被完全绕过。弯曲度似乎取决于饱和度，因为弯曲度随着饱和度的降低而增加。尽管流动模式是曲折的，我们发现，有效的非饱和水力传导率以及保留曲线的三个实现的非均质砂是非常相似的，从而表明这种类型的非均质流系统可以被视为一个等效的均匀介质的有效参数的特征。
Two‐dimensional unsaturated flow and transport through heterogeneous sand was investigated under controlled laboratory conditions. The unsaturated hydraulic conductivity of five homogeneous sands and three heterogeneous systems composed of these five sands was measured using a steady state flux controlled method. The heterogeneous sand systems were established in a laboratory tank for three realizations of random distributions of the homogeneous sands comprising a system of 207 grid cells. The water flux was controlled at the upper boundary, while a suction was applied at the lower boundary such that on the average a uniform pressure profile was established and gravity flow applied. Solute breakthrough curves measured at discrete points in the tank using time domain reflectometry, as well as dye tracer paths, showed that flow and transport took place in a very tortuous pattern where several grid cells were completely bypassed. The degree of tortuosity appeared to be dependent on the degree of saturation, as the tortuosity increased with decreasing saturation. Despite the tortuous flow patterns, we found that the effective unsaturated hydraulic conductivity as well as the retention curves for the three realizations of the heterogeneous sand were quite similar, thus suggesting that this type of heterogeneous flow system can be treated as an equivalent homogeneous medium characterized by effective parameters.