Macropore–Matrix Water Flow Interaction around a Vertical Macropore Embedded in Fine Sand—Laboratory Investigations
Macropore–Matrix Water Flow Interaction around a Vertical Macropore Embedded in Fine Sand—Laboratory Investigations
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细砂中嵌入的垂直大孔周围的大孔-基质水流相互作用——实验室研究
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
J. Braun
中科院分区：
文献类型：
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作者：
K. Germer;J. Braun
在大型容器装置中进行了渗透实验，以研究水通过大孔以及大孔与周围多孔介质基质之间的流动。实验容器高度为120 cm。底座为半圆盘，直径100厘米。集装箱由不锈钢制成，有一个观察玻璃窗作为切面。里面均匀地填满了细沙。沿玻璃面板的中心线垂直放置一个人工大孔。整个过程中嵌入的张力计允许连续观察孔隙水压力头。在向大孔注水过程中，采用间隔摄影技术来观察基质中水前缘的传播情况。结果表明，由于毛细力的作用，水被吸收到周围的基质中，从而耗尽了大孔中的流量。对于初干砂，这种基质-大孔隙相互作用有效地限制了水在大孔隙中的渗透深度。只有经过较长的注入周期（低注入速率时为8 h），同时大孔周围多孔基质含水饱和度增加后，大孔垂直流动才会依次增加，从而探测到向更深层的渗透。在所有注入速率下，对基质中的水分布进行了直观观察，结果表明，在中小流量下，基质中的横向分布暂时主导了大孔隙中的垂直流入。实验设计允许计算水在大孔和周围基质之间流动的传递速度。此外，传递速度可能与周围细粒砂基质中的水压水头有关。在这里，观察到从干燥到潮湿条件下的传递速度明显下降。对所得的传递速度进行了讨论，并与其他作者的类似实验结果进行了比较。这些实验提供了大量的数据集，从而为测试和改进数值模型奠定了良好的基础。
Infiltration experiments were conducted in a large‐scale container setup to investigate water flow through a macropore and between the macropore and the surrounding porous media matrix. The experimental container had a height of 120 cm. Its base was a half disk with a diameter of 100 cm. The container was built from stainless steel with an observation glass window as a section plane. It was homogeneously filled with fine sand. An artificial macropore was placed vertically along the centerline of the glass pane. Tensiometers embedded throughout allowed for a continuous observation of pore water pressure heads. During the injection of water into the macropore, interval photography was employed to visualize the propagation of the water front in the matrix. It was shown that water is being imbibed into the surrounding matrix due to capillary forces, thus depleting the discharge in the macropore. For initially dry sand, this matrix–macropore interaction effectively limits the penetration depth of water inside the macropore. Only after long injection periods (>8 h for low injection rates) with a concurrent increase in water saturation in the porous matrix around the macropore does the vertical macropore flow increase successively and thus a penetration to deeper zones is detected. For all injection rates the water distribution in the matrix was observed visually and showed that for small and medium flow rates the lateral distribution in the matrix temporarily predominated the vertical inflow in the macropore. The experimental design allowed for the calculation of transfer velocity in water flows between the macropore and the surrounding matrix. Furthermore the transfer velocities could be related to the water pressure head in the surrounding fine‐grained sand matrix. Here a distinct decrease of transfer velocity from dry to wet conditions was observed. The transfer velocities obtained were discussed and compared with the results from similar experiments conducted by other authors. These experiments provide a large data set and thus a sound basis for testing and improving numerical models.