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Browsing by Subject Vadose Zone

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Showing results 6 to 9 of 9
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  • The Effect of Drying around Power Cables on the Vadose Zone Temperature

    • Authors: Hruška, M;  Advisor: -;  Participants: Clauser, C.; De Doncker, R.W. (2018)

  • The critical isotherm is assessed by the temperature at which the steepest change occurs in the moisture content with temperature. We considered the impact of the properties of the surrounding medium and of the ambient temperature and moisture content on the dry‐out temperature. We found that seasonal variations in ambient conditions in a field in Italy have a greater impact on the critical temperature than the variations in soil properties in that field (under the assumption of a nearly uniform moisture content with depth). However, our analysis shows that, under certain conditions, a change in the van Genuchten parameter n and in a specific combination of parameters that we call a d...
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  • Undrained Shear Strength of Unsaturated Soils under Zero or Low Confining Pressures in the Vadose Zone

    • Authors: Oh, T.W.;  Advisor: -;  Participants: Vanapalli, S. (2018)

  • In geotechnical engineering practice, many projects such as stability analysis of slopes or trenches and pavement design involve soils in vadose zones at shallow depths, where soils are under unsaturated conditions. For these types of projects, undrained shear strength test results obtained under zero or low confining pressure can be effectively used to analyze the behaviors of unsaturated soils. Experimental procedures to determine the undrained shear strength for different soil suction values, however, is time consuming even under low confining pressure. For this reason, we attempted to develop a semi‐empirical model to predict the undrained shear strength of unsaturated soils at a ...
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  • UZIG Research: Measurement and Characterization of Unsaturated Zone Processes under Wide‐Ranging Climates and Changing Conditions

    • Authors: Trost, J.J.;  Advisor: -;  Participants: Perkins, K.S.; Henson, W.; Mirus, B.B.; Nimmo, J.R.; Muñoz-Carpena, R. (2018)

  • We summarize key findings from 14 papers, several of which originated from a meeting convened by UZIG in 2017 at the University of Florida in Gainesville titled “Land‐Use Change, Climate Change, and Hydrologic Extremes: Unsaturated Zone Responses and Feedbacks.” This special section of Vadose Zone Journal contains multidisciplinary research in three general categories relevant to measuring and understanding unsaturated zone responses to changing land uses and climate: (i) unsaturated zone properties and processes; (ii) soil–plant–atmosphere interactions; and (iii) novel field sampling devices. A strong cross‐cutting theme in these papers is the value of continuous monitoring data and ...
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  • Vadose Zone Gas Migration and Surface Effluxes after a Controlled Natural Gas Release into an Unconfined Shallow Aquifer

    • Authors: Forde, O.N. .;  Advisor: -;  Participants: Mayer, K.U.; Cahill, A.G; Mayer, B.; Cherry, J.A.; Parker, B.L. (2018)

  • This paper presents results from vadose zone gas and surface efflux monitoring during a natural gas release experiment at Canadian Forces Base Borden, Alliston, Ontario, Canada. Over 72 d, 51 m3 of natural gas (>93% CH4) was injected into a shallow, unconfined sand aquifer at depths of 4.5 and 9 m. Methane and CO2 effluxes in combination with soil gas concentrations and stable C isotopic signatures were used to quantify the spatiotemporal migration and fate of injected gas. Preferential gas migration pathways led to vadose zone hot spots, with CH4 concentrations exceeding the lower explosive limit (5% v/v). From these hot spots, episodic surface CH4 effluxes (temporally exceeding 2500...