Unsaturated Soil Mechanics: Fundamental Challenges, Breakthroughs, and Opportunities

Lu, Ning

doi:10.1061/(asce)gt.1943-5606.0002233

Cited by 55 publications

(23 citation statements)

References 58 publications

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“…We cannot exclude that some of the apparent differences are due to the limited capabilities of the method. Instead, we intend to contribute an easily applicable method for further studies of the interplay between RWU, SF and transpiration (Schymanski et al, 2009;Lu et al, 2020). The presented measurements may be a means to complement the analyses of the links between the subsurface and stand organisation (Metzger et al, 2017) and the transpiration of trees (Renner et al, 2016).…”

Section: Effects Of the Sites And Controls For Rwumentioning

confidence: 99%

“…It is well known that the controls of transpiration are not static (Renner et al, 2016;Dubbert and Werner, 2019). Plants can adapt their water uptake and transport to their assimilation under different stressors (Schymanski et al, 2009;Lu et al, 2020). Additionally, plants can store water to buffer intermediate stresses (Cermak et al, 2007;Gao et al, 2014), resulting in deviations between RWU and SF.…”

Section: Introductionmentioning

confidence: 99%

“…In that sense, spatially distributed monitoring of both RWU from soil moisture and SF could help to elucidate differences between the influence of the geological and pedological settings on water supply and the influence of the plants themselves, i.e. their adaptations in root systems, dynamic sourcing of water (Nadezhdina et al, 2010) and transpiration regulation (Lu et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

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Estimates of tree root water uptake from soil moisture profile dynamics

et al. 2020

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Abstract. Root water uptake (RWU), as an important process in the terrestrial water cycle, can help us to better understand the interactions in the soil–plant–atmosphere continuum. We conducted a field study monitoring soil moisture profiles in the rhizosphere of beech trees at two sites with different soil conditions. We present an algorithm to infer RWU from step-shaped, diurnal changes in soil moisture. While this approach is a feasible, easily implemented method for moderately moist and homogeneously textured soil conditions, limitations were identified during drier states and for more heterogeneous soil settings. A comparison with the time series of xylem sap velocity underlines that RWU and sap flow (SF) are complementary measures in the transpiration process. The high correlation between the SF time series of the two sites, but lower correlation between the RWU time series, suggests that soil characteristics affect RWU of the trees but not SF.

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Section: Effects Of the Sites And Controls For Rwumentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimates of tree root water uptake from soil moisture profile dynamics

et al. 2020

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“…In many cases, pore water in the soil is not completely frozen at subzero temperatures due to the soil grain matrix effect (Andersland & Ladanyi, 2004), which includes the surface tension of pore water, the size of pore, and the adsorption of soil grain to water (Lu, 2020; Scherer, 1999). The correlation between unfrozen water content and temperature is described by the phase composition curve (Anderson & Tice, 1972; Liu & Yu, 2013; Lovell, 1957).…”

Section: Introductionmentioning

confidence: 99%

A Simplified Model for the Phase Composition Curve of Saline Soils Considering the Second Phase Transition

Wang

Liu

et al. 2021

Water Resources Research

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Phase composition curves are the basis for the thermo‐hydraulic analysis of saline soil in cold regions. Two types of phase transition, namely, the water‐ice and solution‐crystal phase transitions, would occur in saline soils due to the variation in temperature and migration of moisture and solute, and the occurrence order of the two types of phase transition is governed by the initial salt and water content. This study proposed a conceptual model for the water phase composition curve in saline soils by simplifying the correlation between pore solution properties and soil grain. This model was subsequently applied to the analysis of phase composition characteristics and explained the occurrence of a second phase transition in saline soil. The model was validated by the experimental data from known soils and showed both good results and ease of use when compared to three previous models. The conceptual model provides a convenient and intuitive way to understand the phase composition characteristics of pore solution in saline soil in cold regions and is also easy to use in the thermo‐hydraulic analysis such as the prediction of unfrozen water content and solute concentration.

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“…In particular, hydraulic properties of the vadose zone such as soil water retention curve and unsaturated hydraulic conductivity regulate the amount of water stored in the soil and drained into fractured bedrock and streams (Hammond et al, 2019) and thus could be the dominating parameters influencing the hydraulic partitioning in the critical zones in, for example, mountainous western United States. In addition to critical zone hydrology, the hydraulic properties of unsaturated soils are also important in other disciplines such as agriculture engineering (Kirkham, 2014), geotechnical engineering (Lu, 2020), and environmental sciences (Leme & Miguel, 2018).…”

Section: Introductionmentioning

confidence: 99%

Coupled inversion of hydraulic and self‐potential data from transient outflow experiments to estimate soil petrophysical properties

Xie

Cui

Niu

2021

Vadose Zone Journal

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Hydraulicproperties of soils could play an important role in affecting the partitioning of precipitation in the critical zone. In addition to traditional approaches, in the last two decades, many geophysical methods have been used to aid the hydrologic characterization and measurement of geological materials. In particular, the self-potential (SP) method shows great potential in these hydrogeophysical applications. The objective of this study is to evaluate whether the addition of SP data can improve the estimation of hydraulic properties of soils in an outflow experiment. A stochastic, coupled hydrogeophysical inversion was developed, in which the governing equations were solved using the finite volume method and the parameter estimation was conducted using a Bayesian approach associated with the Markov chain Monte Carlo technique. The results show that the addition of SP data in the inversion could reduce the uncertainty related to the estimated hydraulic parameters of soils and the length of the associated 95% confidence interval can be shortened by ∼1/3. It is also shown that the electrical properties of soils at saturated and unsaturated conditions may also be estimated from the outflow experiment when SP data are available. Compared with hydraulic parameters, the accuracy of the estimated electrical properties is slightly lower. Among them, the saturated streaming potential coupling coefficient C sat has the highest accuracy and lowest uncertainty since C sat directly influences the magnitude of SP signals. The accuracy of other electrical parameters is lower than that of C sat (and hydraulic parameters), and the associated uncertainty can be one order of magnitude larger.

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Unsaturated Soil Mechanics: Fundamental Challenges, Breakthroughs, and Opportunities

Cited by 55 publications

References 58 publications

Estimates of tree root water uptake from soil moisture profile dynamics

Estimates of tree root water uptake from soil moisture profile dynamics

A Simplified Model for the Phase Composition Curve of Saline Soils Considering the Second Phase Transition

Coupled inversion of hydraulic and self‐potential data from transient outflow experiments to estimate soil petrophysical properties

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