The Technical Challenges for Applying Unsaturated Soil Sensors to Conduct Laboratory-Scale Seepage Experiments

Abstract

Although many unsaturated soil experiments have successfully delivered positive outcomes, most studies just concisely illustrated sensor techniques, because their main objectives focused on bridging research gaps. Inexperienced research fellows might rarely follow up those techniques, so they could encounter very trivial and skill-demanding difficulties, undermining the quality of experimental outcomes. With a motivation to avoid those, this work introduces technical challenges in applying three sensor techniques: high precision tensiometer, spatial time-domain reflectometry (spatial TDR) and digital bench scales, which were utilized to measure three fundamental variables: soil suction, moisture content and accumulative outflow. The technical challenges are comprehensively elaborated from five aspects: the functional mechanism, assembling/manufacturing approaches, installation procedure, simultaneous data-logging configurations and post data/signal processing. The conclusions drawn in this work provide sufficient technical details of three sensors in terms of the aforementioned five aspects. This work aims to facilitate any new research fellows who carry out laboratory-scale soil column tests using the three sensors mentioned above. It is also expected that this work will salvage any experimenters having troubleshooting issues with those sensors and help researchers bypass those issues to focus more on their primary research interests.

Mechanisms and Early Warning Strategies of Geotechnical Disasters

“…KEYWORDS land utilization type, groundwater balance, groundwater Since initiating China's modernization and globalization in the 1990s and accelerating the process of urbanization in the 2000s, the spatiotemporal variations of land utilization types have become the most straightforward manifestation of an expansion of human activities (e.g., the rapid expansion of cultivated and construction areas in recent decades). Meanwhile, underground aqueous resources, such as soil moisture in the vadose zone Ma et al, 2015;Yan et al, 2022a;Yan et al, 2022b), perched water Freeze and Cherry, 1979;Izbicki et al, 2015;Liu J. et al, 2019), shallow groundwater (Charbeneau and Sherif, 2002;Hancock, 2002;Hu et al, 2021), are scarce in arid and semi-arid regions. More adversely, the surging demand for water consumption leads to a nonnegligible groundwater table drawdown in these regions (Claessens et al, 2009;Chen et al, 2010;Lei-hua et al, 2012).…”

“…First and foremost, the saturated condition was only considered in the triaxial tests. However, the in-situ might encounter a partially saturated condition, which requires technical support of unsaturated soil seepage and mechanism (Yan et al, 2022a). Second, trapping bubbles inside the pore structure can be further considered as a mechanism reducing friction between interparticle, which might lead to different research findings compared to a fully saturated condition (Ma et al, 2015;.…”

Measurement of In-Situ Flow Rate in Borehole by Heat Pulse Flowmeter: Field-Case Study and Reflection

“…Usually, the seepage measurement could be conducted in the laboratory based on seepage testing standards [13][14][15] or innovative testing platforms [16] with novel sensor techniques [17]. Those standard and novel seepage tests have also been combined with computational fluid dynamic (CFD) models to better understand seepage mechanics at the pore scale [18][19][20][21].…”

Discrete Bubble Flow in Granular Porous Media via Multiphase Computational Fluid Dynamic Simulation

“…where ϕ s is the total porosity; ϕ r is the residual porosity to the total porosity; α, n, m and L are the Van Genuchten (1980) parameters, which depend on the soil type. These parameters could be determined using unsaturated soil tests, including standard tests and soil column tests (Yan et al, 2021a) with various unsaturated soil sensors (Yan et al, 2022a). This approach described above can simulate continuous gas phase transport in the soil layer, driven by pressure.…”