Abstract The effect of preferential flow (PF) in loess is of direct interest as flood irrigation is commonly found in loess regions where precipitation is scarce. This study was to assess the applicability of time-lapse electrical resistivity tomography (ERT) data on monitoring infiltration in loess and to analyze the effects of preexisting preferential path on infiltration process at a localized scale. An in situ single-ring infiltrometer (SRI) test was conducted above a preexisting near-surface crack under a constant influx (10 cm water head for 8 h), and the test was monitored by the means of 2-D time-lapse ERT and validated by an exploratory trench. The ERT results observed some increasing uncertainties in the electrical resistivity in part due to daily temperature variation; however, they showed that the infiltration process under the presence of preferential path can be effectively monitored by time-lapse ERT with a combination of unit electrode spacing (UES). The test results showed a high relative reduction of electrical resistivity (>80%) due to matrix flow (MF) and PF within 0–0.5 h of the test, and followed by a transformation of preferential flow to a more matrix-dominated unsaturated flow, i.e. preferential-to-matrix flow (PMF), with continuous downward progression into the deeper subsurface (greater than 1.2 m) while MF stagnated at the near-surface (about 0.4 m). The results suggested that the presence of even a near-surface preferential path significantly accelerate the infiltration into the deeper loess by the means of PMF, as compared to observed slow infiltration of pure matrix flow in previous studies.

中文翻译：

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使用延时电阻率层析成像技术对黄土中的优先渗透进行现场监测

摘要 黄土中优先流 (PF) 的影响具有直接意义，因为洪水灌溉普遍存在于降水稀少的黄土地区。本研究旨在评估延时电阻率层析成像 (ERT) 数据在监测黄土渗透方面的适用性，并在局部尺度上分析预先存在的优先路径对渗透过程的影响。在恒定流入量（10 cm 水头，持续 8 小时）下，在预先存在的近地表裂纹上方进行原位单环渗透计 (SRI) 测试，并通过二维延时 ERT 监测测试并通过探槽验证。ERT 结果观察到电阻率的一些不确定性增加，部分原因是每日温度变化；然而，他们表明，在优先路径存在下的渗透过程可以通过延时 ERT 与单位电极间距 (UES) 的组合进行有效监测。测试结果表明，在测试后 0-0.5 小时内，由于基质流动 (MF) 和 PF，电阻率相对降低 (>80%)，随后优先流动转变为更多以基质为主的不饱和流动，即优先矩阵流 (PMF)，连续向下推进到更深的地下（大于 1.2 m），而 MF 停滞在近地表（约 0.4 m）。结果表明，与先前研究中观察到的纯基质流的缓慢渗透相比，即使是近地表优先路径的存在也显着加速了通过 PMF 向更深黄土的渗透。