Publications

Grouped by Topic

Agroecology & Conservation

  1. Intercropping With Two Native Woody Shrubs Improves Water Status and Development of Interplanted Groundnut and Pearl Millet in the Sahel.
    Bogie, N. A., Bayala, R., Diedhiou, I., Dick, R., & Ghezzehei, T. A.
    Plant and Soil, 1-2, 143–159. 2019.

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    Abstract

    Aims\{To investigate the physiological responses of groundnut (Arachis hypogea) and pearl millet (Penisetum glaucum) that were intercropped with the native evergreen woody shrubs Piliostigma reticulatum (D.C.) Hochst and Guiera senegalensis J.F. Gmel compared to control crops throughout two growing seasons at two sites with contrasting climate and soil types in Senegal. Methods\{Shrubs grown in groundnut and millet fields at higher than native density were coppiced annually with aboveground biomass returned to the soil and no additional fertilizer. Crop leaf area index (LAI), handheld normalized difference vegetation index (NDVI), leaf water potential, and soil moisture and temperature were monitored in 2012–2013. Results\{At the drier site, the presence of shrubs reduced soil temperature at 5 cm depth by up to 5 °C during early crop growth. Shrub presence increased LAI by up to 266%, NDVI by up to 217% and increased groundnut leaf water potential throughout the day at the wetter site. Shrub effects on crop physiology were stronger overall at the drier site. Conclusions\{These results improve the understanding of how this unique agroforestry system alters the growing environment and the physiological response of associated crops throughout the season.

    BibTeX

    @article{p2019-Bogie-et-al-c,
      author = {Bogie, N.A. and Bayala, R. and Diedhiou, I. and Dick, R. and Ghezzehei, T.A.},
      doi = {10.1007/s11104-018-3882-4},
      journal = {Plant and Soil},
      status = {published},
      volume = {1-2},
      pages = {143–159},
      month = jan,
      sort-word = {agroecology},
      title = {Intercropping With Two Native Woody Shrubs Improves Water Status and Development of Interplanted Groundnut and Pearl Millet in the Sahel},
      year = {2019}
    }
    
  2. Alteration of soil physical properties and processes after ten years of intercropping with native shrubs in the Sahel.
    Bogie, N., Bayala, R., Diedhiou, I., Dick, R. P., & Ghezzehei, T. A.
    Soil and Tillage Research, 182, 153–163. 2018.

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    Abstract

    Scarcity of plant available water is a major challenge for rainfed agriculture throughout the Sahel. At two long-term experiments in Central and Southern Senegal, optimized intercropping with native woody shrubs, Piliostigma reticulatum (DC.) Hochst or Guiera senegalensis J.F. Gmel, (elevated densities and annual coppiced biomass returned to soils) have shown significant improvement of soil-plant-water relations, nutrient availability, and crop yields. The objective was to investigate soil physical properties to develop a mechanistic understanding for the observed improvement of water dynamics due to optimized shrub intercropping. The field experiments had a split-plot factorial design with shrubs as the main factor and fertilizer rate (0, 0.5, 1.0. 1.5 times the recommended addition of N-P-K fertilizer) as the subplot factor. This experiment was carried out at the sites of Keur Matar Arame (Keur Matar) with G. senegalensis and Nioro du Rip (Nioro) with P. reticulatum. Water retention characteristic, unsaturated hydraulic conductivity, surface evaporation, and surface infiltration were measured in the zero fertilizer treatment. At Keur Matar samples were collected from crop + shrub plots near (<0.5 m) the shrub canopy (CSn), crop + shrub plots far (>1 m) from the canopy (CSf) and in crop only plots (CO). At Nioro samples were taken in CSn, CSf, CO, and also from bare soil with no crops or shrubs growing (BS). Infiltration in CO plots compared to CSn plots was 75% and 28% higher at Keur Matar and Nioro, respectively. At Keur Matar water retention was significantly higher at wilting point (−1.5 MPa) in the CSn treatment than in the CSf treatment with values of 0.030 and 0.016 m3 m−3, respectively. At Nioro there was no significant difference in wilting point water content between treatments. These results indicate that shrubs slow down soil water as it infiltrates in the sandy soils and that the large additions of shrub biomass over a ten year period has had a small but significant effect on water retention at wilting point. This study highlights the role that shrub presence and biomass additions play in altering centimeter-scale soil properties.

    BibTeX

    @article{p2018-Bogie-et-al,
      author = {Bogie, N and Bayala, R. and Diedhiou, I. and Dick, R.P. and Ghezzehei, T. A.},
      doi = {10.1016/j.still.2018.05.010},
      status = {published},
      journal = {Soil and Tillage Research},
      keywords = {Soil structure, Sahel, Agroforestry},
      month = may,
      pages = {153--163},
      sort-word = {agroecology},
      title = {Alteration of soil physical properties and processes after ten years of intercropping with native shrubs in the Sahel},
      volume = {182},
      year = {2018},
      bdsk-url-1 = {https://doi.org/10.1016/j.still.2018.05.010}
    }
    
  3. Hydraulic Redistribution by Native Sahelian Shrubs: Bioirrigation to Resist In-Season Drought.
    Bogie, N. A., Bayala, R., Diedhiou, I., Conklin, M. H., Fogel, M., Dick, R., & Ghezzehei, T. A.
    Frontiers in Environmental Science: Agroecology & Land Use Systems, 6, 98. 2018.

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    Abstract

    Hydraulic redistribution (HR) by woody vegetation has been proposed as a potential water source for crops in intercropped systems. The native woody shrub, Guiera senegalensis J.F. Gmel, grows in the fields of farmers across the African Sahel and has shown profound yield benefits to associated pearl millet (Pennisetum glaucum) crops, especially in drought years. We tested whether this benefit resulted from the shrubs performing hydraulic redistribution (HR) with pearl millet using some of this HR water. During an experimentally imposed drought, an enriched deuterium (2H) water tracer applied to 1 m deep roots of G. senegalensis shrubs was detected (2H ≥ +300‰) in aboveground stems of intercropped millet within 12–96 h of tracer introduction. The only viable path for the 2H-enriched H2O into millet was via HR by the shrubs, which confirmed active HR during the time when growing millet was under severe drought stress. Millet biomass production when intercropped with shrubs was over 900% greater than crops grown without shrubs present. Improvement of growing conditions previously found near shrubs cannot fully account for the benefit to associated millet under extreme drought stress without considering the positive impact of the transfer of HR water. This finding illuminates HR and water transfer as an important mechanism in a successful agroforestry system in a region where food security is a serious issue.

    BibTeX

    @article{p2018-Bogie-et-al-b,
      author = {Bogie, NA and Bayala, R and Diedhiou, I and Conklin, MH and Fogel, M and Dick, R and Ghezzehei, TA},
      doi = {10.3389/fenvs.2018.00098},
      status = {published},
      journal = {Frontiers in Environmental Science: Agroecology \& Land Use Systems},
      pages = {98},
      pdf = {http://www.readcube.com/articles/10.3389/fenvs.2018.00098},
      sort-word = {agroecology},
      title = {Hydraulic Redistribution by Native Sahelian Shrubs: Bioirrigation to Resist In-Season Drought},
      volume = {6},
      year = {2018},
      bdsk-url-1 = {https://doi.org/10.3389/fenvs.2018.00098}
    }
    

Aggregation & Soil Structure

  1. Using Wastewater in Irrigation: The Effects on Infiltration Process in a Clayey Soil.
    Albalasmeh, A. A., Gharaibeh, M. A., Alghzawi, M. Z., Morbidelli, R., Saltalippi, C., Ghezzehei, T. A., & Flammini, A.
    Water, 12(4), 968. 2020.

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    Abstract

    Soil water infiltration is a critical process in the soil water cycle and agricultural practices, especially when wastewater is used for irrigation. Although research has been conducted to evaluate the changes in the physical and chemical characteristics of soils irrigated by treated wastewater, a quantitative analysis of the effects produced on the infiltration process is still lacking. The objective of this study is to address this issue. Field experiments previously conducted on three adjacent field plots characterized by the same clayey soil but subjected to three different irrigation treatments have been used. The three irrigation conditions were: non-irrigated (natural conditions) plot, irrigated plot with treated wastewater for two years, and irrigated plot with treated wastewater for five years. Infiltration measurements performed by the Hood infiltrometer have been used to estimate soil hydraulic properties useful to calibrate a simplified infiltration model widely used under ponding conditions, that were existing during the irrigation stage. Our simulations highlight the relevant effect of wastewater usage as an irrigation source in reducing cumulative infiltration and increasing overland flow as a result of modified hydraulic properties of soils characterized by a lower capacity of water drainage. These outcomes can provide important insights for the optimization of irrigation techniques in arid areas where the use of wastewater is often required due to the chronic shortage of freshwater.

    BibTeX

    @article{p2020-Albalasmeh-et-al,
      title = {Using Wastewater in Irrigation: The Effects on Infiltration Process in a Clayey Soil},
      author = {Albalasmeh, Ammar A. and Gharaibeh, Mamoun A. and Alghzawi, Ma’in Z. and Morbidelli, Renato and Saltalippi, Carla and Ghezzehei, Teamrat A. and Flammini, Alessia.},
      doi = {10.3390/w12040968},
      pdf = {https://www.mdpi.com/2073-4441/12/4/968/pdf},
      sort-word = {CO2 flux, Soil respiration, Soil Carbon, aggregation, modeling,biogeoscience},
      journal = {Water},
      status = {published},
      volume = {12},
      number = {4},
      pages = {968},
      year = {2020}
    }
    
  2. Soil structure is an important omission in Earth System Models.
    Fatichi, S., OR, D., Walko, R., Vereecken, H., Young, M. H., Ghezzehei, T. A., … Avissar, R.
    Nature Communications, 11, 522. 2020.

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    Abstract

    Most soil hydraulic information used in Earth System Models (ESMs) is derived from pedo-transfer functions that use easy-to-measure soil attributes to estimate hydraulic parameters. This parameterization relies heavily on soil texture, but overlooks the critical role of soil structure originated by soil biophysical activity. Soil structure omission is pervasive also in sampling and measurement methods used to train pedotransfer functions. Here we show how systematic inclusion of salient soil structural features of biophysical origin affect local and global hydrologic and climatic responses. Locally, including soil structure in models significantly alters infiltration-runoff partitioning and recharge in wet and vegetated regions. Globally, the coarse spatial resolution of ESMs and their inability to simulate intense and short rainfall events mask effects of soil structure on surface fluxes and climate. Results suggest that although soil structure affects local hydrologic response, its implications on global-scale climate remains elusive in current ESMs.

    BibTeX

    @article{p2020-Fatichi-et-al,
      title = {Soil structure is an important omission in Earth System Models},
      author = {Fatichi, Simone and OR, Dani and Walko, Robert and Vereecken, Harry and Young, Michael H. and Ghezzehei, Teamrat A. and Hengl, Tomislav and Kollet, Stefan and Agam, Nurit and Avissar, Roni},
      doi = {10.1038/s41467-020-14411-z},
      sort-word = {CO2 flux, Soil respiration, Soil Carbon, aggregation, modeling,biogeoscience},
      journal = {Nature Communications},
      status = {published},
      pdf = {https://www.nature.com/articles/s41467-020-14411-z.pdf},
      data = {https://static-content.springer.com/esm/art%3A10.1038%2Fs41467-020-14411-z/MediaObjects/41467_2020_14411_MOESM3_ESM.zip},
      mendeley = {https://www.mendeley.com/catalogue/47459482-43dc-319e-95bf-b9110c277f4e/},
      volume = {11},
      pages = {522},
      year = {2020}
    }
    
  3. Effect of Cover Crop on Carbon Distribution in Size and Density Separated Soil Aggregates.
    Schaefer, M. V., Bogie, N. A., Rath, D., Marklein, A. R., Garniwan, A., Haensel, T., … Ying, S. C.
    Soil Systems, 4(1), 6. 2020.

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    Abstract

    Increasing soil organic carbon (SOC) stocks in agricultural soils can contribute to stabilizing or even lowering atmospheric greenhouse gas (GHG) concentrations. Cover crop rotation has been shown to increase SOC and provide productivity benefits for agriculture. Here we used a split field design to evaluate the short-term effect of cover crop on SOC distribution and chemistry using a combination of bulk, isotopic, and spectroscopic analyses of size-and density-separated soil aggregates. Macroaggregates (>250 µm) incorporated additional plant material with cover crop as evidenced by more negative δ13C values (−25.4‰ with cover crop compared to −25.1‰ without cover crop) and increased phenolic (plant-like) resonance in carbon NEXAFS spectra. Iron EXAFS data showed that the Fe pool was composed of 17–21% Fe oxide with the remainder a mix of primary and secondary minerals. Comparison of oxalate and dithionite extractions suggests that cover crop may also increase Fe oxide crystallinity, especially in the dense (>2.4 g cm−3) soil fraction. Cover crop δ13C values were more negative across density fractions of bulk soil, indicating the presence of less processed organic carbon. Although no significant difference was observed in bulk SOC on a mass per mass basis between cover and no cover crop fields after one season, isotopic and spectroscopic data reveal enhanced carbon movement between aggregates in cover crop soil

    BibTeX

    @article{p2020-Schaefer-et-al,
      title = {Effect of Cover Crop on Carbon Distribution in Size and Density Separated Soil Aggregates},
      author = {Schaefer, Michael V and Bogie, Nathaniel A and Rath, Daniel and Marklein, Alison R and Garniwan, Abdi and Haensel, Thomas and Lin, Ying and Avila, Claudia C and Nico, Peter S and Scow, Kate M and Brodie, Eoin L. and Riley, William J. Riley and Fogel, Marilyn L. and Berhe, Asmeret Asefaw and Ghezzehei, Teamrat A. andParikh, Sanjai and Keiluweit, Marco and Ying, Samantha C.},
      doi = {10.3390/soilsystems4010006},
      sort-word = {CO2 flux, Soil respiration, Soil Carbon, aggregation, modeling,biogeoscience},
      journal = {Soil Systems},
      status = {published},
      volume = {4},
      number = {1},
      pages = {6},
      year = {2020},
      publisher = {Multidisciplinary Digital Publishing Institute}
    }
    
  4. On the role of soil water retention characteristic on aerobic microbial respiration.
    Ghezzehei, T. A., Sulman, B., Arnold, C. L., Bogie, N. A., & Berhe, A. A.
    Biogeosciences, 16, 1187–1209. 2019.

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    Abstract

    Soil water status is one of the most important environmental factors that control microbial activity and rate of soil organic matter decomposition (SOM). Its effect can be partitioned into effect of water energy status (water potential) on cellular activity, effect of water volume on cellular motility and aqueous diffusion of substrate and nutrients, as well as effect of air content and gas-diffusion pathways on concentration of dissolved oxygen. However, moisture functions widely used in SOM decomposition models are often based on empirical functions rather than robust physical foundations that account for these disparate impacts of soil water. The contributions of soil water content and water potential vary from soil to soil according to the soil water characteristic (SWC), which in turn is strongly dependent on soil texture and structure. The overall goal of this study is to introduce a physically based modelling framework of aerobic microbial respiration that incorporates the role of SWC under arbitrary soil moisture status. The model was tested by compariing it with published datasets of SOM decomposition under laboratory conditions.

    BibTeX

    @article{p2019-Ghezzehei-et-al,
      author = {Ghezzehei, Teamrat A. and Sulman, Benjamin and Arnold, Chelsea L. and Bogie, Nathaniel A. and Berhe, Asmeret Asefaw},
      doi = {10.5194/bg-16-1187-2019},
      data = {10.6084/m9.figshare.7749332},
      pdf = {https://bg.copernicus.org/articles/16/1187/2019/bg-16-1187-2019.pdf},
      sort-word = {CO2 flux, Soil respiration, Soil Carbon, aggregation, modeling,biogeoscience},
      journal = {Biogeosciences},
      status = {published},
      volume = {16},
      pages = {1187-1209},
      month = mar,
      title = {On the role of soil water retention characteristic on aerobic microbial respiration},
      year = {2019}
    }
    
  5. Soil Structural Degradation during Low-severity Burns.
    Jian, M., Berli, M., & Ghezzehei, T. A.
    Geophysical Research Letters, 45(5553-5561). 2018.

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    Abstract

    Low-severity wildfires and prescribed burns have been steadily increasing for over three decades, currently accounting for more than half of total burned area in the Southwestern United States. Most observations immediately after low-severity burns report little adverse impacts on soil properties and processes. In a few studies, however, significant deterioration of soil structure has been observed several months after such fires. Here we show that rapid vaporization of pore water during low-severity burns raises pneumatic gas pressure inside large aggregates (20-30 mm) to damaging levels; on the order of aggregate tensile strength and high-enough to cause visco-plastic deformation. However, the impact on soil structure was not immediately perceptible. This suggests that other natural forces, such as wetting-drying and thermal cycles, are required to disrupt the weakened aggregates. Thus, adverse consequences of the suggested mechanism on soil processes and services (e.g., infiltration, erodibility, and organic matter protection) are likely overlooked.

    BibTeX

    @article{p2018-Jian-Berli-Ghezzehei,
      author = {Jian, Mathew and Berli, Markus and Ghezzehei, Teamrat A.},
      data = {10.6084/m9.figshare.6349469.v1},
      date-added = {2018-05-27 06:01:51 +0000},
      date-modified = {2018-11-14 14:17:28 -0800},
      doi = {10.1029/2018GL078053},
      journal = {Geophysical Research Letters},
      status = {published},
      month = may,
      number = {5553-5561},
      sort-word = {soil structure, aggregation},
      title = {Soil Structural Degradation during Low-severity Burns},
      volume = {45},
      year = {2018},
      bdsk-url-1 = {https://doi.org/10.1029/2018GL078053}
    }
    
  6. Decomposition of distinct organic matter pools is regulated by moisture status in structured wetland soils.
    Arnold, C., Berhe, A. A., & Ghezzehei, T. A.
    Soil Biology and Biochemistry, 81, 28–37. 2015.

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    Abstract

    Peatlands are garnering much attention for their greenhouse gas feedback potential in a warming climate. As of yet, the coupled biogeochemical and hydrological processes that control the amount and timing of soil organic matter (SOM) mineralization and, ultimately, whether peatlands will be sinks or sources of atmospheric CO 2 are not fully understood. Soil structure is a key feature of soils that mediates the coupling between biogeochemical and hydrological processes. However, we know very little about how soil structure responds when soils are exposed to wettingedrying cycles outside their normal range. In order to better understand how high elevation peatlands will respond to increasingly dry years, we incubated soils from high elevation meadows in the Sierra Nevada at 5 different water potentials and measured the CO 2 flux for over one year. We found that the cumulative carbon mineralization had a U-shaped pattern, with the greatest mineralization at the wettest (À0.1 bar) and driest (À4 bar) water potentials, across all hydrologic regions of the meadow. We propose a conceptual model that reproduces a similar pattern by incorporating the concept of dual porosity medium, with two distinct pore-size populations representing inter-and intra-aggregate porosity. Availability of water and oxygen to the two pore-size populations depends on the soil’s equilibrium water potential. The model and the data suggest that the decomposition rates of intra-aggregate SOM may increase due to prolonged drought events that lead to accelerated release of C from previously untapped pool.

    BibTeX

    @article{p2015-Arnold-Ghezzehei-Berhe,
      author = {Arnold, Chelsea and Berhe, Asmeret Asefaw and Ghezzehei, Teamrat A.},
      doi = {10.1016/j.soilbio.2014.10.029},
      journal = {Soil Biology and Biochemistry},
      status = {published},
      keywords = {CO2 flux, Soil respiration, Hydrology, Meadows, Climate extremes, Soil structure},
      month = sep,
      pages = {28-37},
      researchgate = {https://www.researchgate.net/publication/268630795_Decomposition_of_distinct_organic_matter_pools_is_regulated_by_moisture_status_in_structured_wetland_soils},
      sort-word = {aggregation, biogeoscience},
      title = {Decomposition of distinct organic matter pools is regulated by moisture status in structured wetland soils},
      volume = {81},
      year = {2015}
    }
    
  7. Stress-induced volume reduction of isolated pores in wet soil.
    Ghezzehei, T. A., & Or, D.
    Water Resources Research, 39(3). 2003.

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    Abstract

    This study deals with deformation of small pores in wet soils of relatively high bulk density such as in the final settlement phase of tilled or disturbed soils. Pore deformation was modeled by volume reduction of spherical voids embedded in a homogenous soil matrix. External constant stress and overburden were considered as steady stresses because the change in interaggregate contact stress under overburden is slow compared to the associated strain rate. In contrast, stress due to passage of farm implements was considered as transient because the rate of change of interaggregate stress is comparable with the strain rate. Rheological behavior of the soil matrix under steady and transient stresses was obtained from independent rheological measurements. Experimental data from the literature were used to illustrate the model. Model predictions of relative density compared favorably with experimental data for constant stress application as well as for constant strain rate experiments. Results showed that the rate of densification decreased as the relative density approached unity (complete pore closure) and the relative stress required for driving densification increased exponentially with increasing relative density.

    BibTeX

    @article{p2003-Ghezzehei-Or-b,
      author = {Ghezzehei, Teamrat A. and Or, Dani},
      date-modified = {2018-05-27 19:55:55 +0000},
      journal = {Water Resources Research},
      status = {published},
      month = mar,
      number = {3},
      sort-word = {aggregation},
      title = {Stress-induced volume reduction of isolated pores in wet soil},
      volume = {39},
      year = {2003}
    }
    
  8. Analytical Models for Soil Pore-Size Distribution After Tillage.
    Leij, F. J., Ghezzehei, T. A., & Or, D.
    Soil Science Society of America Journal, 66(4), 1104. 2002.

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    Abstract

    Tillage causes soil fragmentation thereby increasing the proportion of interaggregate (structural) pore space. The resulting tilled layer tends to be structurally unstable as manifested by a gradual decrease in interaggregate porosity until a new equilibrium has been reached between external loads and internal capillary forces at a rate governed by the soil rheological properties. The soil pore-size distribution (PSD) will change accordingly with time. We have previously applied the Fokker-Planck equation (FPE) to describe the evolution of the PSD as the result of drift, dispersion, and degradation processes that affect the pore space in unstable soils. In this study, we provide closed-form solutions for PSD evolution, which can be used to predict temporal behavior of unsaturated soil hydraulic properties. Solutions and moments of the PSD were obtained in case: (i) drift and degradation coefficients depend on time and the dispersivity is constant and (ii) drift and dispersivity are also linearly related to pore size. Both solutions can model the reduction in pore size during the growing season while the second solution can account for a reduction in the dispersion of the PSD. The solutions for PSD were plotted for a mathematically convenient expression for the drift and degradation coefficients and for an expression derived from a model for soil aggregate coalescence. Experimental data on the settlement of a Millville (coarse-silty, carbonatic, mesic Typic Haploxeroll) silt loam during wetting and drying cycles were used to determine time-dependent drift and degradation coefficients according to this coalescence model. The solution for the PSD was used to independently predict the water retention curve, which exhibited a satisfactory agreement with experimental retention data at the end of two drying cycles.

    BibTeX

    @article{p2002-Leij-Ghezzehei-Or-b,
      author = {Leij, Feike J. and Ghezzehei, Teamrat A. and Or, Dani},
      date-modified = {2018-05-31 01:37:35 +0000},
      journal = {Soil Science Society of America Journal},
      status = {published},
      number = {4},
      pages = {1104},
      researchgate = {https://www.researchgate.net/publication/37450945_Analytical_Models_for_Soil_Pore-Size_Distribution_After_Tillage},
      sort-word = {aggregation},
      title = {Analytical Models for Soil Pore-Size Distribution After Tillage},
      volume = {66},
      year = {2002}
    }
    
  9. Modeling post-tillage soil structural dynamics: a review.
    Or, D., & Ghezzehei, T. A.
    Soil and Tillage Research, 64(1-2), 41–59. 2002.

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    Abstract

    Tillage modifies the soil structure to create conditions favorable for plant growth. However, the resulting loose structure is susceptible to collapse by internal capillary forces and external compactive stresses with concurrent changes in soil hydraulic properties. Presently, limited understanding of these complex processes often leads to consideration of the soil plow-layer as a static porous medium. Our objective is to provide a review of recent progress in modeling soil structural dynamics at the pore-scale, based on soil mechanical and rheological properties. The basic geometrical framework of the models was a cubic arrangement of monosized spherical aggregates (other arrangements are discussed). The process of soil aggregate rejoining by capillary forces was modeled by considering the rate of energy dissipation due to viscous deformation of wet soil, and corresponding energy release due to reconfiguration of water capillary menisci. The model was complemented by independent rheological characterization of soil that provides control on the rate as well as the onset and termination of aggregate coalescence. The model was also adapted for consideration of steady stress (such as overburden) acting upon the unit cells. Unlike steady stress, transient stress (such as traffic) is applied for too short of a period to allow for total energy dissipation by viscous deformation. Hence, a portion of the deformation is elastic (with a recoverable portion of the applied energy). Rheological characterization under transient (oscillatory) stress provided coupled elastic and viscous properties under several loading frequencies. Effects of transient stresses on the geometrical model were modeled by considering a combination of (i) Hertzian-type elastic strain and (ii) viscous flow of soil at the contacts. Application of the models is demonstrated using illustrative examples and rheological measurements of Millville silt loam soil. Finally, we provide an outlook for upscaling the unit cell results to an aggregate bed scale.

    BibTeX

    @article{p2002-Or-Ghezzehei,
      author = {Or, D and Ghezzehei, T. A.},
      date-modified = {2018-05-31 01:36:51 +0000},
      journal = {Soil and Tillage Research},
      status = {published},
      keywords = {Rheology, Soil-structure, Compaction, Aggregate},
      number = {1-2},
      pages = {41-59},
      researchgate = {https://www.researchgate.net/publication/222697340_Modeling_post-tillage_soil_structural_dynamics_A_review},
      sort-word = {aggregation},
      title = {Modeling post-tillage soil structural dynamics: a review},
      volume = {64},
      year = {2002}
    }
    
  10. Modeling the dynamics of the soil pore-size distribution.
    Leij, F. J., Ghezzehei, T. A., & Or, D.
    Soil and Tillage Research, 64(1-2), 61–78. 2002.

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    Abstract

    Soil tillage often results in a structurally unstable soil layer with an elevated inter-aggregate porosity that is gradually decreased by the interplay of capillary and rheological processes. We have previously proposed to describe the evolution of the pore-size distribution (PSD) with the Fokker–Planck equation (FPE). The coefficients of this equation quantify the drift, dispersion, and degradation processes acting upon the PSD. An analytical solution for the PSD is presented for the case where drift and degradation coefficients depend on time, and the dispersion coefficient is proportional to the drift coefficient. These coefficients can be estimated from independent measurements of the PSD or (surrogate) water retention data or from mechanistic models. In this paper, we illustrate the application of the pore-size evolution model for: (i) a generic drift coefficient, (ii) static water retention data for soils under different tillage regimes, and (iii) dynamic hydraulic data for a soil subject to a sequence of wetting and drying cycles. These applications show the viability of our approach to model pore-size evolution. However, the development and application of the model is hampered by a lack of definitive data on soil structural and hydraulic dynamics.

    BibTeX

    @article{p2002-Leij-Ghezzehei-Or,
      author = {Leij, FJ and Ghezzehei, TA and Or, D},
      date-modified = {2018-05-31 01:36:25 +0000},
      journal = {Soil and Tillage Research},
      status = {published},
      keywords = {Soil hydraulic properties, Compaction, Wetting, Drying, Pore-size distribution, Analytical solution},
      number = {1-2},
      pages = {61-78},
      researchgate = {https://www.researchgate.net/publication/222696315_Modeling_the_dynamics_of_the_soil_pore-size_distribution_Soil_Tillage_Reseach},
      sort-word = {aggregation},
      title = {Modeling the dynamics of the soil pore-size distribution},
      volume = {64},
      year = {2002}
    }
    
  11. Rheological Properties of Wet Soils and Clays under Steady and Oscillatory Stresses.
    Ghezzehei, T. A., & Or, D.
    Soil Science Society of America Journal, 65(3), 624. 2001.

    Details BibTeX

    Abstract

    Tilled agricultural soils are in a constant state of change induced by variations in soil strength due to wetting and drying and compaction by farm implements. Changes in soil structure affect many hydraulic and transport properties; hence their quantification is critical for accu- rate hydrological and environmental modeling. This study highlights the role of soil rheology in determining time-dependent stress–strain relationships that are essential for prediction and analysis of structural changes in soils. The primary objectives of this study were (i) to extend a previously proposed aggregate-pair model to prediction of compaction under external steady or transient stresses and (ii) to provide experimentally determined rheological information for the above models. Rheological properties of soils and clay minerals were measured with a rotational rheometer with parallel-plate sensors. These measurements, under controlled steady shear stress application, have shown that wet soils have viscoplastic behavior with well-defined yield stress and nearly constant plastic viscosity. In contrast, rapid transient loading (e.g., passage of a tractor) is often too short for complete viscous dissipation of applied stress, resulting in an elastic (recoverable) component of deformation (viscoelastic behavior). Measured viscoelastic properties were expressed by complex viscosity and shear modulus whose components denote viscous energy dissipa- tion, and energy storage (elastic). Results show that for low water contents and fast loading (tractor speed), the elastic component of deformation increases, whereas with higher water contents, viscosity and shear modulus decrease. Steady and oscillatory stress application to an aggregate pair model illustrates potential use of rheological properties towards obtaining predictions of strains in soils.

    BibTeX

    @article{p2001-Ghezzehei-Or,
      author = {Ghezzehei, Teamrat A. and Or, Dani},
      date-modified = {2018-05-30 21:37:12 +0000},
      journal = {Soil Science Society of America Journal},
      status = {published},
      number = {3},
      pages = {624},
      researchgate = {https://www.researchgate.net/publication/37450913_Rheological_Properties_of_Wet_Soils_and_Clays_under_Steady_and_Oscillatory_Stresses},
      sort-word = {aggregation, mechanics},
      title = {Rheological Properties of Wet Soils and Clays under Steady and Oscillatory Stresses},
      volume = {65},
      year = {2001}
    }
    
  12. Stochastic model for posttillage soil pore space evolution.
    Or, D., Leij, F. J., Snyder, V., & Ghezzehei, T. A.
    Water Resources Research, 36(7), 1641–1652. 2000.

    Details BibTeX

    Abstract

    Tillage operations disrupt surface layers of agricultural soils, creating a loosened structure with a substantial proportion of interaggregate porosity that enhances liquid and gaseous exchange properties favorable for plant growth. Unfortunately, such desirable soil tilth is structurally unstable and is susceptible to change by subsequent wetting and drying processes and other mechanical stresses that reduce total porosity and modify pore size distribution (PSD). Ability to model posttillage dynamics of soil pore space and concurrent changes in hydraulic properties is important for realistic predictions of transport processes through this surface layer. We propose a stochastic modeling framework that couples the probabilistic nature of pore space distributions with physically based soil deformation models using the Fokker‐Planck equation (FPE) formalism. Three important features of soil pore space evolution are addressed: (1) reduction of the total porosity, (2) reduction of mean pore radius, and (3) changes in the variance of the PSD. The proposed framework may be used to provide input to hydrological models concerning temporal variations in near‐surface soil hydraulic properties. In a preliminary investigation of this approach we link a previously proposed mechanistic model of soil aggregate coalescence to the stochastic FPE framework to determine the FPE coefficients. An illustrative example is presented which describes changes in interaggregate pore size due to wetting‐drying cycles and the resulting effects on dynamics of the soil water characteristic curve and hydraulic conductivity functions.

    BibTeX

    @article{p2000-Or-etal,
      author = {Or, D and Leij, FJ and Snyder, V and Ghezzehei, T. A.},
      date-modified = {2018-05-30 21:36:47 +0000},
      journal = {Water Resources Research},
      status = {published},
      month = jul,
      number = {7},
      pages = {1641-1652},
      researchgate = {https://www.researchgate.net/publication/37450896_Stochastic_model_for_post-tillage_soil_pore_size_evolution},
      sort-word = {aggregation},
      title = {Stochastic model for posttillage soil pore space evolution},
      volume = {36},
      year = {2000},
      bdsk-url-1 = {https://doi.org/10.1029/2000WR900092}
    }
    
  13. Dynamics of soil aggregate coalescence governed by capillary and rheological processes.
    Ghezzehei, T. A., & Or, D.
    Water Resources Research, 36(2), 367–379. 2000.

    Details BibTeX

    Abstract

    The desired soil structure following tillage of agricultural soils is often unstable and susceptible to coalescence of aggregates and reduction of interaggregate porosity due to wetting and drying cycles. This process of aggregate rejoining was modeled by equating the rate of work done by liquid‐vapor menisci, to the rate of energy dissipation due to viscous deformation of a pair of spherical aggregates. The nonlinearity of wet soil viscous flow behavior was accounted for by introducing a Bingham rheological model. A natural outcome of the analysis was the formulation of a mathematical condition for the onset and termination of coalescence based on soil strength at specified water content. The condition states that sufficient energy in excess of soil strength (yield stress) must be available for coalescence to proceed. The rate of aggregate coalescence is proportional to available energy and is inversely related to the coefficient of plastic viscosity. Transport of wet soil to the periphery of the interaggregate contact by viscous flow leads to smoothing of the neck, resulting in pore closure, on the one hand, and restricting the minimum matric potential that can be achieved, on the other. The interplay between rheology and geometry prevent coalescence from proceeding indefinitely. Independently determined soil rheological properties were used to illustrate the use of the model. Coalescence under constant water content and during wetting‐drying cycles was calculated. Comparison of data from experiments on one‐dimensional, aggregate bed settlement has shown reasonable agreement with the model predictions.

    BibTeX

    @article{p2000-Ghezzehei-Or,
      author = {Ghezzehei, T. A. and Or, D.},
      date-modified = {2018-05-30 21:21:45 +0000},
      journal = {Water Resources Research},
      status = {published},
      month = feb,
      number = {2},
      pages = {367-379},
      researchgate = {https://www.researchgate.net/publication/37450893_Dynamics_of_soil_aggregate_coalescence_governed_by_capillary_and_rheological_processes},
      sort-word = {soil structure, aggregation},
      title = {Dynamics of soil aggregate coalescence governed by capillary and rheological processes},
      volume = {36},
      year = {2000},
      bdsk-url-1 = {https://doi.org/10.1029/1999WR900316}
    }
    

Nuclear Waste

  1. Modeling Coupled Evaporation and Seepage in Ventilated Cavities.
    Ghezzehei, T. A., Trautz, R. C., Finsterle, S., Cook, P. J., & Ahlers, C. F.
    Vadose Zone Journal, 3(3), 806–818. 2004.

    Details BibTeX

    Abstract

    Cavities excavated in unsaturated geological formations are important to activities such as nuclear waste disposal and mining. Such cavities provide a unique setting for simultaneous occurrence of seepage and evaporation. Previously, inverse numerical modeling of field liquid-release tests and associated seepage into cavities were used to provide seepage-related large-scale formation properties, ignoring the impact of evaporation. The applicability of such models was limited to the narrow range of ventilation conditions under which the models were calibrated. The objective of this study was to alleviate this limitation by incorporating evaporation into the seepage models. We modeled evaporation as an isothermal vapor diffusion process. The semiphysical model accounts for the relative humidity (RH), temperature, and ventilation conditions of the cavities. The evaporation boundary layer thickness (BLT) over which diffusion occurs was estimated by calibration against free-water evaporation data collected inside the experimental cavities. The estimated values of BLT were 5 to 7 mm for the open underground drifts and 20 mm for niches closed off by bulkheads. Compared with previous models that neglected the effect of evaporation, this new approach showed significant improvement in capturing seepage fluctuations into open cavities of low RH. At high relative-humidity values (>85%), the effect of evaporation on seepage was very small.

    BibTeX

    @article{p2004-Ghezzehei-et-al,
      author = {Ghezzehei, T. A. and Trautz, R. C. and Finsterle, S. and Cook, P. J. and Ahlers, C. F.},
      date-modified = {2018-05-27 20:09:29 +0000},
      doi = {10.2136/vzj2004.0806},
      journal = {Vadose Zone Journal},
      status = {published},
      month = aug,
      number = {3},
      pages = {806--818},
      researchgate = {https://www.researchgate.net/publication/236570656_Modeling_coupled_evaporation_and_seepage_in_ventilated_tunnels},
      sort-word = {nuclear waste},
      title = {Modeling Coupled Evaporation and Seepage in Ventilated Cavities},
      volume = {3},
      year = {2004}
    }
    
  2. Dripping into subterranean cavities from unsaturated fractures under evaporative conditions.
    Or, D., & Ghezzehei, T. A.
    Water Resources Research, 36(2), 381–393. 2000.

    Details BibTeX

    Abstract

    Water dripping into subterranean cavities within fractured porous media is studied in order to improve estimates of dripping rates, drop sizes, and chemical composition of droplets that could affect long‐term integrity of waste disposal canisters placed in caverns. Steady state liquid flux in fracture surfaces supported by flow in partially liquid‐filled grooves and liquid films in adjacent planes was calculated as a function of the matric potential (vapor pressure) of the fracture. At an intersection of a vertical fracture with a wider cavity the liquid flux feeds a growing pendant drop that eventually detaches. Equilibrium state size and approximate shape of liquid drops suspended from the cavity ceiling were determined from lateral and vertical force balance considering capillarity, gravity, and hydrostatic pressure. A one‐dimensional, viscous extension model with appropriate gravitational and surface tension components was employed to determine dripping rate from specified fracture roughness geometry as a function of matric potential (flux). The effect of evaporation from drop surface during drop formation was incorporated; the resulting alterations in drop volume, dripping rate, and drop solute concentration were determined. To facilitate experimental testing of the proposed model, a decoupled solution that considers independently controlled flux and evaporation is presented. Under evaporative conditions, dripping in finite period is possible only when volumetric flux exceeds evaporative demand. Calculations indicate that dripping rate and solute concentration are extremely sensitive to ambient matric potential. The results of this work may be extended to study other phenomena including formation and growth of stalactites and rivulet flow in cave ceilings.

    BibTeX

    @article{p2000-Or-Ghezzehei,
      author = {Or, D and Ghezzehei, T. A.},
      date-modified = {2018-05-30 21:36:21 +0000},
      journal = {Water Resources Research},
      status = {published},
      month = feb,
      number = {2},
      pages = {381-393},
      researchgate = {https://www.researchgate.net/publication/37450895_Dripping_into_cavities_from_unsaturated_fractures_under_evaporative_conditions},
      sort-word = {nuclear},
      title = {Dripping into subterranean cavities from unsaturated fractures under evaporative conditions},
      volume = {36},
      year = {2000},
      bdsk-url-1 = {https://doi.org/10.1029/1999WR900311}
    }
    

Nuclear Waste

  1. Modeling Coupled Evaporation and Seepage in Ventilated Cavities.
    Ghezzehei, T. A., Trautz, R. C., Finsterle, S., Cook, P. J., & Ahlers, C. F.
    Vadose Zone Journal, 3(3), 806–818. 2004.

    Details BibTeX

    Abstract

    Cavities excavated in unsaturated geological formations are important to activities such as nuclear waste disposal and mining. Such cavities provide a unique setting for simultaneous occurrence of seepage and evaporation. Previously, inverse numerical modeling of field liquid-release tests and associated seepage into cavities were used to provide seepage-related large-scale formation properties, ignoring the impact of evaporation. The applicability of such models was limited to the narrow range of ventilation conditions under which the models were calibrated. The objective of this study was to alleviate this limitation by incorporating evaporation into the seepage models. We modeled evaporation as an isothermal vapor diffusion process. The semiphysical model accounts for the relative humidity (RH), temperature, and ventilation conditions of the cavities. The evaporation boundary layer thickness (BLT) over which diffusion occurs was estimated by calibration against free-water evaporation data collected inside the experimental cavities. The estimated values of BLT were 5 to 7 mm for the open underground drifts and 20 mm for niches closed off by bulkheads. Compared with previous models that neglected the effect of evaporation, this new approach showed significant improvement in capturing seepage fluctuations into open cavities of low RH. At high relative-humidity values (>85%), the effect of evaporation on seepage was very small.

    BibTeX

    @article{p2004-Ghezzehei-et-al,
      author = {Ghezzehei, T. A. and Trautz, R. C. and Finsterle, S. and Cook, P. J. and Ahlers, C. F.},
      date-modified = {2018-05-27 20:09:29 +0000},
      doi = {10.2136/vzj2004.0806},
      journal = {Vadose Zone Journal},
      status = {published},
      month = aug,
      number = {3},
      pages = {806--818},
      researchgate = {https://www.researchgate.net/publication/236570656_Modeling_coupled_evaporation_and_seepage_in_ventilated_tunnels},
      sort-word = {nuclear waste},
      title = {Modeling Coupled Evaporation and Seepage in Ventilated Cavities},
      volume = {3},
      year = {2004}
    }
    
  2. Dripping into subterranean cavities from unsaturated fractures under evaporative conditions.
    Or, D., & Ghezzehei, T. A.
    Water Resources Research, 36(2), 381–393. 2000.

    Details BibTeX

    Abstract

    Water dripping into subterranean cavities within fractured porous media is studied in order to improve estimates of dripping rates, drop sizes, and chemical composition of droplets that could affect long‐term integrity of waste disposal canisters placed in caverns. Steady state liquid flux in fracture surfaces supported by flow in partially liquid‐filled grooves and liquid films in adjacent planes was calculated as a function of the matric potential (vapor pressure) of the fracture. At an intersection of a vertical fracture with a wider cavity the liquid flux feeds a growing pendant drop that eventually detaches. Equilibrium state size and approximate shape of liquid drops suspended from the cavity ceiling were determined from lateral and vertical force balance considering capillarity, gravity, and hydrostatic pressure. A one‐dimensional, viscous extension model with appropriate gravitational and surface tension components was employed to determine dripping rate from specified fracture roughness geometry as a function of matric potential (flux). The effect of evaporation from drop surface during drop formation was incorporated; the resulting alterations in drop volume, dripping rate, and drop solute concentration were determined. To facilitate experimental testing of the proposed model, a decoupled solution that considers independently controlled flux and evaporation is presented. Under evaporative conditions, dripping in finite period is possible only when volumetric flux exceeds evaporative demand. Calculations indicate that dripping rate and solute concentration are extremely sensitive to ambient matric potential. The results of this work may be extended to study other phenomena including formation and growth of stalactites and rivulet flow in cave ceilings.

    BibTeX

    @article{p2000-Or-Ghezzehei,
      author = {Or, D and Ghezzehei, T. A.},
      date-modified = {2018-05-30 21:36:21 +0000},
      journal = {Water Resources Research},
      status = {published},
      month = feb,
      number = {2},
      pages = {381-393},
      researchgate = {https://www.researchgate.net/publication/37450895_Dripping_into_cavities_from_unsaturated_fractures_under_evaporative_conditions},
      sort-word = {nuclear},
      title = {Dripping into subterranean cavities from unsaturated fractures under evaporative conditions},
      volume = {36},
      year = {2000},
      bdsk-url-1 = {https://doi.org/10.1029/1999WR900311}
    }
    

Nuclear Waste

  1. Modeling Coupled Evaporation and Seepage in Ventilated Cavities.
    Ghezzehei, T. A., Trautz, R. C., Finsterle, S., Cook, P. J., & Ahlers, C. F.
    Vadose Zone Journal, 3(3), 806–818. 2004.

    Details BibTeX

    Abstract

    Cavities excavated in unsaturated geological formations are important to activities such as nuclear waste disposal and mining. Such cavities provide a unique setting for simultaneous occurrence of seepage and evaporation. Previously, inverse numerical modeling of field liquid-release tests and associated seepage into cavities were used to provide seepage-related large-scale formation properties, ignoring the impact of evaporation. The applicability of such models was limited to the narrow range of ventilation conditions under which the models were calibrated. The objective of this study was to alleviate this limitation by incorporating evaporation into the seepage models. We modeled evaporation as an isothermal vapor diffusion process. The semiphysical model accounts for the relative humidity (RH), temperature, and ventilation conditions of the cavities. The evaporation boundary layer thickness (BLT) over which diffusion occurs was estimated by calibration against free-water evaporation data collected inside the experimental cavities. The estimated values of BLT were 5 to 7 mm for the open underground drifts and 20 mm for niches closed off by bulkheads. Compared with previous models that neglected the effect of evaporation, this new approach showed significant improvement in capturing seepage fluctuations into open cavities of low RH. At high relative-humidity values (>85%), the effect of evaporation on seepage was very small.

    BibTeX

    @article{p2004-Ghezzehei-et-al,
      author = {Ghezzehei, T. A. and Trautz, R. C. and Finsterle, S. and Cook, P. J. and Ahlers, C. F.},
      date-modified = {2018-05-27 20:09:29 +0000},
      doi = {10.2136/vzj2004.0806},
      journal = {Vadose Zone Journal},
      status = {published},
      month = aug,
      number = {3},
      pages = {806--818},
      researchgate = {https://www.researchgate.net/publication/236570656_Modeling_coupled_evaporation_and_seepage_in_ventilated_tunnels},
      sort-word = {nuclear waste},
      title = {Modeling Coupled Evaporation and Seepage in Ventilated Cavities},
      volume = {3},
      year = {2004}
    }
    
  2. Dripping into subterranean cavities from unsaturated fractures under evaporative conditions.
    Or, D., & Ghezzehei, T. A.
    Water Resources Research, 36(2), 381–393. 2000.

    Details BibTeX

    Abstract

    Water dripping into subterranean cavities within fractured porous media is studied in order to improve estimates of dripping rates, drop sizes, and chemical composition of droplets that could affect long‐term integrity of waste disposal canisters placed in caverns. Steady state liquid flux in fracture surfaces supported by flow in partially liquid‐filled grooves and liquid films in adjacent planes was calculated as a function of the matric potential (vapor pressure) of the fracture. At an intersection of a vertical fracture with a wider cavity the liquid flux feeds a growing pendant drop that eventually detaches. Equilibrium state size and approximate shape of liquid drops suspended from the cavity ceiling were determined from lateral and vertical force balance considering capillarity, gravity, and hydrostatic pressure. A one‐dimensional, viscous extension model with appropriate gravitational and surface tension components was employed to determine dripping rate from specified fracture roughness geometry as a function of matric potential (flux). The effect of evaporation from drop surface during drop formation was incorporated; the resulting alterations in drop volume, dripping rate, and drop solute concentration were determined. To facilitate experimental testing of the proposed model, a decoupled solution that considers independently controlled flux and evaporation is presented. Under evaporative conditions, dripping in finite period is possible only when volumetric flux exceeds evaporative demand. Calculations indicate that dripping rate and solute concentration are extremely sensitive to ambient matric potential. The results of this work may be extended to study other phenomena including formation and growth of stalactites and rivulet flow in cave ceilings.

    BibTeX

    @article{p2000-Or-Ghezzehei,
      author = {Or, D and Ghezzehei, T. A.},
      date-modified = {2018-05-30 21:36:21 +0000},
      journal = {Water Resources Research},
      status = {published},
      month = feb,
      number = {2},
      pages = {381-393},
      researchgate = {https://www.researchgate.net/publication/37450895_Dripping_into_cavities_from_unsaturated_fractures_under_evaporative_conditions},
      sort-word = {nuclear},
      title = {Dripping into subterranean cavities from unsaturated fractures under evaporative conditions},
      volume = {36},
      year = {2000},
      bdsk-url-1 = {https://doi.org/10.1029/1999WR900311}
    }
    

Nuclear Waste

  1. Modeling Coupled Evaporation and Seepage in Ventilated Cavities.
    Ghezzehei, T. A., Trautz, R. C., Finsterle, S., Cook, P. J., & Ahlers, C. F.
    Vadose Zone Journal, 3(3), 806–818. 2004.

    Details BibTeX

    Abstract

    Cavities excavated in unsaturated geological formations are important to activities such as nuclear waste disposal and mining. Such cavities provide a unique setting for simultaneous occurrence of seepage and evaporation. Previously, inverse numerical modeling of field liquid-release tests and associated seepage into cavities were used to provide seepage-related large-scale formation properties, ignoring the impact of evaporation. The applicability of such models was limited to the narrow range of ventilation conditions under which the models were calibrated. The objective of this study was to alleviate this limitation by incorporating evaporation into the seepage models. We modeled evaporation as an isothermal vapor diffusion process. The semiphysical model accounts for the relative humidity (RH), temperature, and ventilation conditions of the cavities. The evaporation boundary layer thickness (BLT) over which diffusion occurs was estimated by calibration against free-water evaporation data collected inside the experimental cavities. The estimated values of BLT were 5 to 7 mm for the open underground drifts and 20 mm for niches closed off by bulkheads. Compared with previous models that neglected the effect of evaporation, this new approach showed significant improvement in capturing seepage fluctuations into open cavities of low RH. At high relative-humidity values (>85%), the effect of evaporation on seepage was very small.

    BibTeX

    @article{p2004-Ghezzehei-et-al,
      author = {Ghezzehei, T. A. and Trautz, R. C. and Finsterle, S. and Cook, P. J. and Ahlers, C. F.},
      date-modified = {2018-05-27 20:09:29 +0000},
      doi = {10.2136/vzj2004.0806},
      journal = {Vadose Zone Journal},
      status = {published},
      month = aug,
      number = {3},
      pages = {806--818},
      researchgate = {https://www.researchgate.net/publication/236570656_Modeling_coupled_evaporation_and_seepage_in_ventilated_tunnels},
      sort-word = {nuclear waste},
      title = {Modeling Coupled Evaporation and Seepage in Ventilated Cavities},
      volume = {3},
      year = {2004}
    }
    
  2. Dripping into subterranean cavities from unsaturated fractures under evaporative conditions.
    Or, D., & Ghezzehei, T. A.
    Water Resources Research, 36(2), 381–393. 2000.

    Details BibTeX

    Abstract

    Water dripping into subterranean cavities within fractured porous media is studied in order to improve estimates of dripping rates, drop sizes, and chemical composition of droplets that could affect long‐term integrity of waste disposal canisters placed in caverns. Steady state liquid flux in fracture surfaces supported by flow in partially liquid‐filled grooves and liquid films in adjacent planes was calculated as a function of the matric potential (vapor pressure) of the fracture. At an intersection of a vertical fracture with a wider cavity the liquid flux feeds a growing pendant drop that eventually detaches. Equilibrium state size and approximate shape of liquid drops suspended from the cavity ceiling were determined from lateral and vertical force balance considering capillarity, gravity, and hydrostatic pressure. A one‐dimensional, viscous extension model with appropriate gravitational and surface tension components was employed to determine dripping rate from specified fracture roughness geometry as a function of matric potential (flux). The effect of evaporation from drop surface during drop formation was incorporated; the resulting alterations in drop volume, dripping rate, and drop solute concentration were determined. To facilitate experimental testing of the proposed model, a decoupled solution that considers independently controlled flux and evaporation is presented. Under evaporative conditions, dripping in finite period is possible only when volumetric flux exceeds evaporative demand. Calculations indicate that dripping rate and solute concentration are extremely sensitive to ambient matric potential. The results of this work may be extended to study other phenomena including formation and growth of stalactites and rivulet flow in cave ceilings.

    BibTeX

    @article{p2000-Or-Ghezzehei,
      author = {Or, D and Ghezzehei, T. A.},
      date-modified = {2018-05-30 21:36:21 +0000},
      journal = {Water Resources Research},
      status = {published},
      month = feb,
      number = {2},
      pages = {381-393},
      researchgate = {https://www.researchgate.net/publication/37450895_Dripping_into_cavities_from_unsaturated_fractures_under_evaporative_conditions},
      sort-word = {nuclear},
      title = {Dripping into subterranean cavities from unsaturated fractures under evaporative conditions},
      volume = {36},
      year = {2000},
      bdsk-url-1 = {https://doi.org/10.1029/1999WR900311}
    }