Comparison of Wetting Front Advancing Method and Instantaneous Profile Method for the Hydraulic Conductivity Measurement
Wetting front advancing method is of lower cost and faster experimental progress for measuring the unsaturated hydraulic conductivities. In this paper, a new method is proposed to identify the wetting front, in which the monitored data is used to infer we
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Abstract. Wetting front advancing method is of lower cost and faster experimental progress for measuring the unsaturated hydraulic conductivities. In this paper, a new method is proposed to identify the wetting front, in which the monitored data is used to infer wetting front. Data analysis of three column tests reported by earlier scholar proves that the new method is applicable. Wetting front advancing method can be used to analyze wetting column test data and offer high quality results of unsaturated hydraulic conductivities. The limitation of a clear wetting front that can be observed is not necessary. The remove of this limitation will greatly expand the applicability of the wetting front advancing method. Keywords: Wetting front advancing method Soil column test Instantaneous profile method Unsaturated hydraulic conductivities
1 Introduction Wetting front advancing method (Li et al. 2009) can be used to measure the unsaturated hydraulic conductivities of soil. It is of lower cost and faster experimental progress comparing the instantaneous profile method. Both the capillary rising process (Lu and Likos 2004) and infiltration process can be used in analyzed by the wetting front advancing method. However, the accuracy of these two methods is still lack of a thorough comparison. In this paper, the data of soil column test reported by (Cui et al. 2008; Ng and Leung 2012) are analyzed by both wetting front advancing method and instantaneous profile method. The accuracy of two methods and the key parameters involved in these methods are also discussed.
2 Soil Column Test and the Determination of Wetting Front Advancing Velocity Soil column test is often used to study the water infiltration or capillary process in single layer or multilayer soils (Li et al. 2009). Li et al. (2009) initially reported that a clear wetting front that be observed is required. However, it is not right. In fact, wetting © Springer Nature Singapore Pte Ltd. 2018 L. Hu et al. (Eds.): GSIC 2018, Proceedings of GeoShanghai 2018 International Conference: Multi-physics Processes in Soil Mechanics and Advances in Geotechnical Testing, pp. 47–53, 2018. https://doi.org/10.1007/978-981-13-0095-0_5
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Fig. 1. Soil column test
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Wetting front recorded by sensor Wetting front fitted
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Fig. 2. Fitted wetting front advancing curve
front can be extracted from the monitored data in the cases where no clear wetting front (WF) is observed. As shown in Fig. 1, there are three monitoring sections A, B, and C. If a water content hc is used as an indicator of wetting front, hc may be monitored in sections A, B and C at time of tA , tB and tC , respectively. The distances between the infiltration boundary and sections A, B; and C are hA , hB and hC . The relation between distance and time is plot in Fig. 2 and fitted by exponential function. Further, the wetting front velocity can be extracted as, vð t Þ ¼
@h @t
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