Journal articles on the topic 'Soil hydraulic stress'
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1
Nguyen, Thuy Huu, Matthias Langensiepen, Jan Vanderborght, Hubert Hüging, Cho Miltin Mboh, and Frank Ewert. "Comparison of root water uptake models in simulating CO<sub>2</sub> and H<sub>2</sub>O fluxes and growth of wheat." Hydrology and Earth System Sciences 24, no. 10 (October 23, 2020): 4943–69. http://dx.doi.org/10.5194/hess-24-4943-2020.
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Abstract. Stomatal regulation and whole plant hydraulic signaling affect water fluxes and stress in plants. Land surface models and crop models use a coupled photosynthesis–stomatal conductance modeling approach. Those models estimate the effect of soil water stress on stomatal conductance directly from soil water content or soil hydraulic potential without explicit representation of hydraulic signals between the soil and stomata. In order to explicitly represent stomatal regulation by soil water status as a function of the hydraulic signal and its relation to the whole plant hydraulic conductance, we coupled the crop model LINTULCC2 and the root growth model SLIMROOT with Couvreur's root water uptake model (RWU) and the HILLFLOW soil water balance model. Since plant hydraulic conductance depends on the plant development, this model coupling represents a two-way coupling between growth and plant hydraulics. To evaluate the advantage of considering plant hydraulic conductance and hydraulic signaling, we compared the performance of this newly coupled model with another commonly used approach that relates root water uptake and plant stress directly to the root zone water hydraulic potential (HILLFLOW with Feddes' RWU model). Simulations were compared with gas flux measurements and crop growth data from a wheat crop grown under three water supply regimes (sheltered, rainfed, and irrigated) and two soil types (stony and silty) in western Germany in 2016. The two models showed a relatively similar performance in the simulation of dry matter, leaf area index (LAI), root growth, RWU, gross assimilation rate, and soil water content. The Feddes model predicts more stress and less growth in the silty soil than in the stony soil, which is opposite to the observed growth. The Couvreur model better represents the difference in growth between the two soils and the different treatments. The newly coupled model (HILLFLOW–Couvreur's RWU–SLIMROOT–LINTULCC2) was also able to simulate the dynamics and magnitude of whole plant hydraulic conductance over the growing season. This demonstrates the importance of two-way feedbacks between growth and root water uptake for predicting the crop response to different soil water conditions in different soils. Our results suggest that a better representation of the effects of soil characteristics on root growth is needed for reliable estimations of root hydraulic conductance and gas fluxes, particularly in heterogeneous fields. The newly coupled soil–plant model marks a promising approach but requires further testing for other scenarios regarding crops, soil, and climate.
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Windisch, Étienne J. "The hydraulics problem in slope stability analysis." Canadian Geotechnical Journal 28, no. 6 (December 1, 1991): 903–9. http://dx.doi.org/10.1139/t91-107.
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Hydraulic pressures and forces are obtained on a typical slice, as used in current methods of slope stability analysis, under hydrostatic and flowing groundwater conditions. It is shown that current methods do not satisfy some basic hydraulics and soil mechanics principles. The effective normal stress on the lower boundary of a slice is shown to be underestimated, and the resultant hydraulic force is not accounted for adequately. Key words: effective stress, hydraulic pressure, hydraulic gradient, hydraulic force, slope stability.
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Yang, N., and S. L. Barbour. "The impact of soil structure and confining stress on the hydraulic conductivity of clays in brine environments." Canadian Geotechnical Journal 29, no. 5 (October 1, 1992): 730–39. http://dx.doi.org/10.1139/t92-081.
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Numerous studies have been completed in recent years on the alteration of the hydraulic conductivity of clayey soils as a result of exposure to concentrated organic or inorganic permeants. These hydraulic conductivity changes have been attributed to either changes in microstructure, due to contraction of the diffuse double layer, or to the alteration of the macrostructure, as a result of volume changes leading to shrinkage fractures or fissures. In this paper, the change in hydraulic conductivity of a highly plastic natural clay during exposure to a concentrated sodium chloride (NaCl) solution is described. The performance of samples with three different initial soil structures, prepared by slurry, static compaction, and kneading compaction, were investigated under various levels of confining stress. Hydraulic conductivity tests were carried out before and after the samples were exposed to the NaCl solutions. Scanning electron microscope photography was used to compare the soil structures before and after brine permeation. The test results show that the alteration of hydraulic conductivity is strongly related to the initial soil structure and the level of confining stress. No significant change in the microfabric of the clay was observed; however, the size of the interaggregate pores appeared to increase as a result of the physicochemical volume change that occurred during brine permeation. The increase in hydraulic conductivity that occurred during brine permeation could be prevented by increasing the level of confining stress. The stress levels at which significant increases in hydraulic conductivity occurred appeared to be coincident with low levels of vertical stress which allowed the sample to undergo lateral shrinkage and a subsequent loss of confinement. Key words : hydraulic conductivity, clay soils, osmotic consolidation, sodium chloride brine, soil structure, scanning electron microscope.
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Chen, Meng Qiao, Jian Kun Liu, and Jun Hua Xiao. "Soil Stress of Shield Tunnel Face in Sands under High Hydraulic Pressure." Advanced Materials Research 588-589 (November 2012): 1983–87. http://dx.doi.org/10.4028/www.scientific.net/amr.588-589.1983.
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Based on the under river tunneling project of Nanjing Metro Puzhulu-Binjianglu interval, a numerical model was built to simulate the process of losing stability, variation of soil stress and the soil arching effect caused by soil stress redistribution under high hydraulic pressure were studied. The results show that, compared to no hydraulic pressure, the limit supporting pressure is reached when smaller soil deformation has occurred and it is much greater under high hydraulic pressure. Along the depth from the bottom, soil vertical stress first decreases and then remains unchanged with increasing face displacement; Soil horizontal stress first decreases and then increases slightly. Soil lateral pressure coefficient first increases and then decreases along the depth from the bottom. Soil vertical and horizontal stress decrease in front of the tunnel face, where the failure region forms. Soil vertical stress decreases and horizontal stress increases above the failure region, where the vault region forms. Soil vertical stress increases and horizontal stress decreases around the failure region, where the skewback region forms. The results are conductive to better reveal the failure mechanism and determine the limit supporting pressure under high hydraulic pressure.
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Brom, Jakub, Renata Duffková, Jan Haberle, Antonín Zajíček, Václav Nedbal, Tereza Bernasová, and Kateřina Křováková. "Identification of Infiltration Features and Hydraulic Properties of Soils Based on Crop Water Stress Derived from Remotely Sensed Data." Remote Sensing 13, no. 20 (October 15, 2021): 4127. http://dx.doi.org/10.3390/rs13204127.
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Knowledge of the spatial variability of soil hydraulic properties is important for many reasons, e.g., for soil erosion protection, or the assessment of surface and subsurface runoff. Nowadays, precision agriculture is gaining importance for which knowledge of soil hydraulic properties is essential, especially when it comes to the optimization of nitrogen fertilization. The present work aimed to exploit the ability of vegetation cover to identify the spatial variability of soil hydraulic properties through the expression of water stress. The assessment of the spatial distribution of saturated soil hydraulic conductivity (Ks) and field water capacity (FWC) was based on a combination of ground-based measurements and thermal and hyperspectral airborne imaging data. The crop water stress index (CWSI) was used as an indicator of crop water stress to assess the hydraulic properties of the soil. Supplementary vegetation indices were used. The support vector regression (SVR) method was used to estimate soil hydraulic properties from aerial data. Data analysis showed that the approach estimated Ks with good results (R2 = 0.77) for stands with developed crop water stress. The regression coefficient values for estimation of FWC for topsoil (0–0.3 m) ranged from R2 = 0.38 to R2 = 0.99. The differences within the study sites of the FWC estimations were higher for the subsoil layer (0.3–0.6 m). R2 values ranged from 0.12 to 0.99. Several factors affect the quality of the soil hydraulic features estimation, such as crop water stress development, condition of the crops, period and time of imaging, etc. The above approach is useful for practical applications for its relative simplicity, especially in precision agriculture.
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Andersen, Knut H., Colin G. Rawlings, Tom A. Lunne, and Trond H. By. "Estimation of hydraulic fracture pressure in clay." Canadian Geotechnical Journal 31, no. 6 (December 1, 1994): 817–28. http://dx.doi.org/10.1139/t94-099.
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For offshore drilling, and in particular when drilling from fixed platforms in deep waters, the mud pressure will be high compared with the hydraulic fracture pressure (i.e., the formation strength) close to the sea floor. The first casing (the conductor) should therefore be installed to a depth where the formation strength is sufficient to prevent hydraulic fracturing of the soil. The consequences of hydraulic fracture could be mud flowing into the formation and loss of mud circulation. This slows down the drilling and, in cases where large quantities of mud flow into the formations beneath the platform, may even threaten the integrity of the foundation soils and create a safety problem. A conservative approach with too deep conductor setting depths will, on the other hand, lead to high unnecessary costs. This paper presents a new approach for calculating hydraulic fracture pressures. The new calculation approach considers two important factors that are generally not covered by theories found in the literature: nonlinearity of the stress–strain properties of the soil, and pore-pressure changes in the soil due to changes in total normal stress and shearing of the soil. The stress–strain properties and the shear-induced pore pressure are determined from laboratory tests. The proposed calculation approach has been verified against a series of laboratory model hydraulic fracture tests and in situ hydraulic fracture tests carried out at numerous offshore sites. The paper also presents a rational approach to establish the maximum allowable drilling mud pressure in clay formations and recommends partial safety coefficients that depend upon the consequences of hydraulic fracture and the quality of the soil data. Key words : hydraulic fracture, boreholes, clay, conductor setting depth, model tests, in situ tests, calculations.
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Guérin, Marceau, Georg von Arx, Dario Martin-Benito, Laia Andreu-Hayles, Kevin L. Griffin, Nate G. McDowell, William Pockman, and Pierre Gentine. "Distinct xylem responses to acute vs prolonged drought in pine trees." Tree Physiology 40, no. 5 (January 24, 2020): 605–20. http://dx.doi.org/10.1093/treephys/tpz144.
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Abstract Increasing dryness challenges trees’ ability to maintain water transport to the leaves. Most plant hydraulics models use a static xylem response to water stress. Yet, in reality, lower soil moisture and warmer temperatures during growing seasons feed back onto xylem development. In turn, adjustments to water stress in the newly built xylem influence future physiological responses to droughts. In this study, we investigate the annual variation of anatomical traits in branch xylem in response to different soil and atmospheric moisture conditions and tree stress levels, as indicated by seasonal predawn leaf water potential (ΨL,pd). We used a 6-year field experiment in southwestern USA with three soil water treatments applied to Pinus edulis Engelm trees—ambient, drought (45% rain reduction) and irrigation (15–35% annual water addition). All trees were also subject to a natural 1-year acute drought (soil and atmospheric) that occurred during the experiment. The irrigated trees showed only moderate changes in anatomy-derived hydraulic traits compared with the ambient trees, suggesting a generally stable, well-balanced xylem structure under unstressed conditions. The artificial prolonged soil drought increased hydraulic efficiency but lowered xylem construction costs and decreased tracheid implosion safety ((t/b)2), suggesting that annual adjustments of xylem structure follow a safety–efficiency trade-off. The acute drought plunged hydraulic efficiency across all treatments. The combination of acute and prolonged drought resulted in vulnerable and inefficient new xylem, disrupting the stability of the anatomical trade-off observed in the rest of the years. The xylem hydraulic traits showed no consistent direct link to ΨL,pd. In the future, changes in seasonality of soil and atmospheric moisture are likely to have a critical impact on the ability of P. edulis to acclimate its xylem to warmer climate. Furthermore, the increasing frequency of acute droughts might reduce hydraulic resilience of P. edulis by repeatedly creating vulnerable and less efficient anatomical structure.
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Han, Bowen, Guoqing Cai, Lin Xie, Jian Li, and Chenggang Zhao. "Bounding surface constitutive model for unsaturated soils considering microscopic pore structure and bonding effect." E3S Web of Conferences 195 (2020): 02007. http://dx.doi.org/10.1051/e3sconf/202019502007.
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This article presents a bounding surface model for unsaturated soils by using skeleton stress and bonding variable based on microcosmic pore structure as constitutive variables. A Hydraulic hysteresis soil-water characteristic curve model considering deformation and hydraulic hysteresis is combined to achieve hydraulic coupling. The proposed model can capture the change of the inter-particles bonding effect in the deformation process of unsaturated soils and accurately predict the hydraulic mechanical behavior of unsaturated soils under complicated loading paths and wetting-drying cycles. The validity of the proposed model is confirmed by the results of unsaturated isotropic compression tests, wetting-drying cycles tests and unsaturated triaxial shear tests reported in the literature.
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Ma, Tiantian, Changfu Wei, Pan Chen, Huihui Tian, and De'an Sun. "A Unified Elastoplastic Model of Unsaturated Soils Considering Capillary Hysteresis." Journal of Applied Mathematics 2013 (2013): 1–15. http://dx.doi.org/10.1155/2013/537185.
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Unlike its saturated counterparts, the mechanical behavior of an unsaturated soil depends not only upon its stress history but also upon its hydraulic history. In this paper, a soil-water characteristic relationship which is capable of describing the effect of capillary hysteresis is introduced to characterize the influence of hydraulic history on the skeletal deformation. The capillary hysteresis is viewed as a phenomenon associated with the internal structural rearrangements in unsaturated soils, which can be characterized by using a set of internal state variables. It is shown that both capillary hysteresis and plastic deformation can be consistently addressed in a unified theoretical framework. Within this context, a constitutive model of unsaturated soils is developed by generalizing the modified Cam-Clay model. A hardening function is introduced, in which both the matric suction and the degree of saturation are explicitly included as hardening variables, so that the effect of hydraulic history on the mechanical response can be properly addressed. The proposed model is capable of capturing the main features of the unsaturated soil behavior. The new model has a hierarchical structure, and, depending upon application, it can describe the stress-strain relation and the soil-water characteristics in a coupled or uncoupled manner.
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Nalbantoglu, Zalihe, and Erdil Riza Tuncer. "Compressibility and hydraulic conductivity of a chemically treated expansive clay." Canadian Geotechnical Journal 38, no. 1 (February 1, 2001): 154–60. http://dx.doi.org/10.1139/t00-076.
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The paper presents a series of laboratory tests and evaluates the effect of lime and fly ash on the compressibility and hydraulic characteristics of an expansive soil in Cyprus. The tests were performed at different percentages of lime (07%) and fly ash (15 and 25%) by dry weight of soil, and additional tests were also performed on soils treated with 15% fly ash plus 3% lime. Previously published research reveals that few data are available concerning the compressibility and hydraulic conductivity of lime-treated soils. The results of this study indicate an increase in the vertical effective yield stress (apparent preconsolidation pressure) and a decrease in the compressibility characteristics of the treated soils. Moreover, unlike some of the findings in the literature, higher hydraulic conductivity values were obtained with time. This finding has been substantiated by the reduced cation exchange capacity (CEC) values, which indicate that the pozzolanic reaction causes the soils to become more granular in nature, resulting in higher hydraulic conductivity.Key words: cementation, compressibility, fly ash, hydraulic conductivity, lime.
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Sheng, Daichao, and An-Nan Zhou. "Coupling hydraulic with mechanical models for unsaturated soils." Canadian Geotechnical Journal 48, no. 5 (May 2011): 826–40. http://dx.doi.org/10.1139/t10-109.
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This paper presents an alternative method to couple the hydraulic component with the mechanical component in a constitutive model for unsaturated soils. Some pioneering work on hydromechanical coupling is reviewed. Generalized constitutive relations on coupled hydromechanical behaviour are introduced. These generalized constitutive relations are then incorporated into existing mechanical and hydraulic models for unsaturated soils. A new coupling mechanism is proposed based on the fact that soil-water characteristic equations are usually obtained for constant stress, not constant volume. The proposed coupling mechanism also satisfies the intrinsic relationship between the degree of saturation and the volumetric strain for undrained compression. Numerical examples are presented to show the performance of the proposed model in predicting soil behaviour along drying and loading paths. Finally, the model is validated against experimental data for different soils.
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Sloan, Brandon P., Sally E. Thompson, and Xue Feng. "Plant hydraulic transport controls transpiration sensitivity to soil water stress." Hydrology and Earth System Sciences 25, no. 8 (August 3, 2021): 4259–74. http://dx.doi.org/10.5194/hess-25-4259-2021.
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Abstract. Plant transpiration downregulation in the presence of soil water stress is a critical mechanism for predicting global water, carbon, and energy cycles. Currently, many terrestrial biosphere models (TBMs) represent this mechanism with an empirical correction function (β) of soil moisture – a convenient approach that can produce large prediction uncertainties. To reduce this uncertainty, TBMs have increasingly incorporated physically based plant hydraulic models (PHMs). However, PHMs introduce additional parameter uncertainty and computational demands. Therefore, understanding why and when PHM and β predictions diverge would usefully inform model selection within TBMs. Here, we use a minimalist PHM to demonstrate that coupling the effects of soil water stress and atmospheric moisture demand leads to a spectrum of transpiration responses controlled by soil–plant hydraulic transport (conductance). Within this transport-limitation spectrum, β emerges as an end-member scenario of PHMs with infinite conductance, completely decoupling the effects of soil water stress and atmospheric moisture demand on transpiration. As a result, PHM and β transpiration predictions diverge most for soil–plant systems with low hydraulic conductance (transport-limited) that experience high variation in atmospheric moisture demand and have moderate soil moisture supply for plants. We test these minimalist model results by using a land surface model at an AmeriFlux site. At this transport-limited site, a PHM downregulation scheme outperforms the β scheme due to its sensitivity to variations in atmospheric moisture demand. Based on this observation, we develop a new “dynamic β” that varies with atmospheric moisture demand – an approach that overcomes existing biases within β schemes and has potential to simplify existing PHM parameterization and implementation.
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Yeh, Hsin-Fu, Tsien-Ting Huang, and Jhe-Wei Lee. "Effect of Unimodal and Bimodal Soil Hydraulic Properties on Slope Stability Analysis." Water 13, no. 12 (June 16, 2021): 1674. http://dx.doi.org/10.3390/w13121674.
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Rainfall infiltration is the primary triggering factor of slope instability. The process of rainfall infiltration leads to changes in the water content and internal stress of the slope soil, thereby affecting slope stability. The soil water retention curve (SWRC) was used to describe the relationship between soil water content, matric suction, and the water retention characteristics of the soil. This characteristic is essential for estimating the properties of unsaturated soils, such as unsaturated hydraulic conductivity function and shear strength. Thus, SWRC is regarded as important information for depicting the properties of unsaturated soil. The SWRC is primarily affected by the soil pore size distribution (PSD) and has unimodal and bimodal features. The bimodal SWRC is suitable for soils with structural or dual-porous media. This model can describe the structure of micropores and macropores in the soil and allow the hydraulic behavior at different pore scales to be understood. Therefore, this model is more consistent with the properties of onsite soil. Few studies have explored the differences in the impact of unimodal and bimodal models on unsaturated slopes. This study aims to consider unimodal and bimodal SWRC to evaluate the impact of unsaturated slope stability under actual rainfall conditions. A conceptual model of the slope was built based on field data to simulate changes in the hydraulic behavior of the slope. The results of seepage analysis show that the bimodal model has a better water retention capacity than the unimodal model, and therefore, its water storage performance is better. Under the same saturated hydraulic conductivity function, the wetting front of the bimodal model moves down faster. This results in changes in the pressure head, water content, and internal stress of the soil. The results show that the water content and suction stress changes of the bimodal model are higher than those of the unimodal model due to the difference in water retention capacity. Based on the stability of the slope, calculated using the seepage analysis, the results indicate that the potential failure depth of the bimodal model is deeper than that of the unimodal model.
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Mehdizade, B., H. Asadi, M. Shabanpour, and H. Ghadiri. "Impact of erosion and tillage on the productivity and quality of selected semiarid soils of Iran." International Agrophysics 27, no. 3 (September 1, 2013): 291–97. http://dx.doi.org/10.2478/v10247-012-0097-4.
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Abstract This greenhouse research was carried out to study the effects of water and tillage erosion on agricultural productivity and soil quality in soil samples from a semiarid region of Iran. A factorial experiment of complete randomized block design was used to compare the effects of soil erosion (eroded and non-eroded soils), slope position, water stress and fertilizer (N-P-K) on yield and yield components of wheat as soil productivity index. The results showed that erosion ie water and tillage erosion has a significant effect (p<0.01) in decreasing soil productivity due to its negative impact on soil organic matter, nutrients (N and K) and hydraulic conductivity. Complete N-P-K fertilization and water stress had significant effects on increasing and decreasing of wheat yield, respectively. The effect of water stress in particular was so high that it could eclipse the erosion impact on yield reduction. Wheat dry matter and grain mass on foot and mid slopes were significantly higher than that on upslope positions where total N and available K were the lowest and equivalent calcium carbonate the highest. Saturated hydraulic conductivity and total nitrogen were found to be the most important soil properties as far as their correlations to wheat yield are concerned.
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Li, Duan, Jianhua Si, Xiaoyou Zhang, Yayu Gao, Huan Luo, Jie Qin, and Guanlong Gao. "The Mechanism of Changes in Hydraulic Properties of Populus euphratica in Response to Drought Stress." Forests 10, no. 10 (October 15, 2019): 904. http://dx.doi.org/10.3390/f10100904.
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Stable hydraulic conductivity in forest trees maintains the survival of trees which contribute to productivity in forest ecosystems. Drought conditions break down this relationship, but the mechanisms are poorly known. To increase the understanding of the mechanism of hydraulic characteristics during drought, we determined hydraulic parameters in Populus euphratica Oliv. (P. euphratica) in a time-series of drought using a high-pressure flow meter. We found that P. euphratica could enhance hydraulic transport in severe drought stress under a threshold of soil water content. Drought-induced loss of hydraulic conductance could seriously impair water transport capacity. The soil water content of about 4.5% in the rhizosphere could lead to canopy mortality yet maintain live roots. Hydraulic conductance could be changed under drought stress as a consequence of changes in the anatomical structure and physiology. Furthermore, there was also a trade-off between hydraulic efficiency and safety. The consideration of hydraulic efficiency was first within the range of hydraulic safety limit. Once the hydraulic safety limit was reached, safety would be taken as the first consideration and hydraulic efficiency would be reduced. Research on the mechanism of hydraulic properties in riparian plants in arid areas provides a scientific basis for riparian forest restoration.
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Yang, Wei, Pan Ke Wei, and Ji Ming Sun. "Finite Element Modeling of Hydraulic Excavator in Soil Cutting Process." Applied Mechanics and Materials 145 (December 2011): 240–44. http://dx.doi.org/10.4028/www.scientific.net/amm.145.240.
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A three-dimensional finite element model of hydraulic excavator is proposed to simulate soil cutting. To consider nonlinear soil behaviors, we apply the theory of Arbitrary Lagrangian-Eulerian (ALE) and explicit dynamic method to analyze a large scale fluid-solid structure interaction problem. The elastic-plastic assumption theory is introduced to simulate soil material behavior during the process of soil cutting because the nonlinear elastic-plastic model has advantages of simultaneously accounting for dynamic effects of strain hardening, strain rate, automatic mesh contact with friction capability, soil mechanical behavior and soil-bucket interaction. Soil-bucket interaction is modeled as friction with adhesion depending upon different influencing factors. This paper also investigates the parameters that may cause computational instability in soil cutting analysis. The difficulties in the numerical simulation of soil cutting are overcome by adopting suitable parameters to meet the requirement of proper mesh separation criterion. The proposed modeling can also be used to predict soil stress distribution, soil deformation and Von Mises stress distribution of component in hydraulic excavator.
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Chang, Muhsiung, and Ren-Chung Huang. "Observations of hydraulic fracturing in soils through field testing and numerical simulations." Canadian Geotechnical Journal 53, no. 2 (February 2016): 343–59. http://dx.doi.org/10.1139/cgj-2015-0193.
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Hydraulic fracturing is a potential cause of leakage of earth dams or loss of fluid in drilling and field permeability testing. The effect of hydraulic fracturing on soil grouting is also a major concern. Although hydraulic fracturing has been adopted for decades by the petroleum industry for oil recovery in rock formations, studies on fracturing in soils are relatively few and inconclusive. The aim of this study is to provide further insight into the mechanism of hydrofracturing in soils through a field grouting trial and numerical simulation. We observe hydraulic fracturing in soils during this field trial as predicted by generally accepted groutability requirements. The hydraulic fractures are found vertically developed up to the ground surface. Numerical simulations show the hydraulic fracturing is easier to be initiated in anisotropic stress conditions, where the minor principal stress is the key factor. Numerical simulations also demonstrate significant compressions and shears during injection, suggesting the mechanism of fracturing in soils would be a shearing type. Based on this study, we propose a punching and splitting mode for the hydrofracturing in soils. The equation associated with estimating fracturing pressure is verified, and the results are found to be in good agreement with the cases examined.
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PK, Srivastava, M. Gupta, A. Pandey, V. Pandey, N. Singh, and Tewari SK. "Effects of sodicity induced changes in soil physical properties on paddy root growth." Plant, Soil and Environment 60, No. 4 (April 8, 2014): 165–69. http://dx.doi.org/10.17221/926/2013-pse.
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A study was conducted to investigate the influence of sodicity induced changes in soil physical properties on paddy root growth in the normal agriculture, semi-reclaimed and sodic soils. The root growth (length, length density, biomass and distribution pattern) were unfavourably affected by the soil physical properties (bulk density, soil aggregate stability, available water content, hydraulic conductivity and soil water retention potential) in the case of sodic soil. The microbial biomass carbon, bacterial, fungal population and dehydrogenase activity showed the lower values in the case of sodosol compared to the normal soil. These soil biological properties tend to sustain paddy root growth in normal and semi-reclaimed soils. Principal component analysis revealed that soil physical properties accounted for 98.2% of total variance in root growth. The study revealed that salt stress induces changes in soil physical properties limiting paddy root growth in the salt affected soils. It is important to reclaim sodosols to alleviate salt induced physical stress for optimum paddy root growth.
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Simms, P. H., and E. K. Yanful. "A pore-network model for hydromechanical coupling in unsaturated compacted clayey soils." Canadian Geotechnical Journal 42, no. 2 (April 1, 2005): 499–514. http://dx.doi.org/10.1139/t05-002.
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The behaviour of deformable unsaturated soils is difficult to characterize with simple relationships. Unsaturated hydraulic properties, namely the soil-water characteristic curve and the hydraulic conductivity function, are dependent on both volume change and degree of saturation, whereas volume change itself often cannot be related to a single stress variable but must be described by independent functions of mechanical loading and suction. It is proposed that a means to obtain these functions is through pore-network modelling, by which it is possible to integrate the phenomena of drainage and volume change and the different effects of suction and mechanical loading. The implementation of a two-dimensional pore-network model is described. A simple algorithm for individual pore volume change is adopted. The model uses pore-size distributions measured by mercury intrusion porosimetry to initially generate the simulated pore grid. Predictions of soil-water characteristic curves, void ratio versus suction curves, pore-size distributions at specific suctions, unsaturated hydraulic conductivity, and compression curves are compared with measured values from two compacted clayey soils.Key words: unsaturated soil, volume change, pore network, soil-water characteristic curve, unsaturated hydraulic conductivity, compacted clay.
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Kodikara, J. K., and F. Rahman. "Effects of specimen consolidation on the laboratory hydraulic conductivity measurement." Canadian Geotechnical Journal 39, no. 4 (August 1, 2002): 908–23. http://dx.doi.org/10.1139/t02-036.
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Laboratory hydraulic conductivity tests are commonly used for the design of clayey liners in waste containment. Although relatively small hydraulic gradients are encountered under field conditions, elevated gradients are desirable to reduce the testing time. It is generally believed, however, that these elevated gradients would reduce the conductivity measured owing to specimen consolidation. In the current paper a theoretical analysis is presented for assessing the effect of specimen consolidation. The theoretical results were compared with experimental results obtained for two local soils. Parametric analyses and nondimensional analyses were carried out and the results are presented. It was found that the hydraulic conductivity is dependent on the type of permeameter, the form of gradient application, and the state of stress within the soil. It was apparent that hydraulic conductivity can decrease with an increase in the hydraulic gradient, and the decrease was not significant up to a hydraulic gradient of about 300 for the soils tested.Key words: hydraulic conductivity, hydraulic gradient, specimen consolidation, volume change, permeameter.
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Ellis, Richard J., Christopher M. Taylor, Graham P. Weedon, Nicola Gedney, Douglas B. Clark, and Sietse Los. "Evaluating the Simulated Seasonality of Soil Moisture with Earth Observation Data." Journal of Hydrometeorology 10, no. 6 (December 1, 2009): 1548–60. http://dx.doi.org/10.1175/2009jhm1147.1.
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Abstract A critical function of a land surface scheme, used in climate and weather prediction models, is to partition the energy from insolation into sensible and latent heat fluxes. Many use a soil moisture function to control the surface moisture fluxes through the transpiration. The validity and global distribution of the parameters used to calculate this soil moisture stress function are difficult to assess. This work presents a method to map soil moisture stress globally from an earth observation vegetation index and precipitation data, and it compares the resulting distributions with output from the Joint U.K. Land Environment Simulator (JULES) land surface scheme. A number of model runs with different soil and vegetation parameters are compared. These examine the sensitivity of the seasonality of soil moisture stress, within the model, to the parameterization of soil hydraulic properties and the seasonality of leaf area index in the vegetation. It is found that the seasonality of soil moisture within the model is more sensitive to the soil hydraulic properties than the leaf area index. The partitioning of throughfall into evaporation and runoff, in the model, is the dominant factor in determining the timing of soil moisture stress.
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Rezaei, M., P. Seuntjens, I. Joris, W. Boënne, S. Van Hoey, P. Campling, and W. M. Cornelis. "Sensitivity of water stress in a two-layered sandy grassland soil to variations in groundwater depth and soil hydraulic parameters." Hydrology and Earth System Sciences 20, no. 1 (January 29, 2016): 487–503. http://dx.doi.org/10.5194/hess-20-487-2016.
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Abstract. Monitoring and modelling tools may improve irrigation strategies in precision agriculture. We used non-invasive soil moisture monitoring, a crop growth and a soil hydrological model to predict soil water content fluctuations and crop yield in a heterogeneous sandy grassland soil under supplementary irrigation. The sensitivity of the soil hydrological model to hydraulic parameters, water stress, crop yield and lower boundary conditions was assessed after integrating models. Free drainage and incremental constant head conditions were implemented in a lower boundary sensitivity analysis. A time-dependent sensitivity analysis of the hydraulic parameters showed that changes in soil water content are mainly affected by the soil saturated hydraulic conductivity Ks and the Mualem–van Genuchten retention curve shape parameters n and α. Results further showed that different parameter optimization strategies (two-, three-, four- or six-parameter optimizations) did not affect the calculated water stress and water content as significantly as does the bottom boundary. In this case, a two-parameter scenario, where Ks was optimized for each layer under the condition of a constant groundwater depth at 135–140 cm, performed best. A larger yield reduction, and a larger number and longer duration of stress conditions occurred in the free drainage condition as compared to constant boundary conditions. Numerical results showed that optimal irrigation scheduling using the aforementioned water stress calculations can save up to 12–22 % irrigation water as compared to the current irrigation regime. This resulted in a yield increase of 4.5–6.5 %, simulated by the crop growth model.
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Bonan, G. B., M. Williams, R. A. Fisher, and K. W. Oleson. "Modeling stomatal conductance in the earth system: linking leaf water-use efficiency and water transport along the soil–plant–atmosphere continuum." Geoscientific Model Development 7, no. 5 (September 30, 2014): 2193–222. http://dx.doi.org/10.5194/gmd-7-2193-2014.
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Abstract. The Ball–Berry stomatal conductance model is commonly used in earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must be empirically parameterized. We evaluated the Ball–Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil–plant–atmosphere continuum (SPA). The SPA model simulates stomatal conductance numerically by (1) optimizing photosynthetic carbon gain per unit water loss while (2) constraining stomatal opening to prevent leaf water potential from dropping below a critical minimum. We evaluated two optimization algorithms: intrinsic water-use efficiency (ΔAn /Δgs, the marginal carbon gain of stomatal opening) and water-use efficiency (ΔAn /ΔEl, the marginal carbon gain of transpiration water loss). We implemented the stomatal models in a multi-layer plant canopy model to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using leaf analyses, eddy covariance fluxes at six forest sites, and parameter sensitivity analyses. The primary differences among stomatal models relate to soil moisture stress and vapor pressure deficit responses. Without soil moisture stress, the performance of the SPA stomatal model was comparable to or slightly better than the CLM Ball–Berry model in flux tower simulations, but was significantly better than the CLM Ball–Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from water flow along the soil-to-leaf pathway rather than being imposed a priori, as in the CLM Ball–Berry model. Similar functional dependence of gs on Ds emerged from the ΔAn/ΔEl optimization, but not the ΔAn /gs optimization. Two parameters (stomatal efficiency and root hydraulic conductivity) minimized errors with the SPA stomatal model. The critical stomatal efficiency for optimization (ι) gave results consistent with relationships between maximum An and gs seen in leaf trait data sets and is related to the slope (g1) of the Ball–Berry model. Root hydraulic conductivity (Rr*) was consistent with estimates from literature surveys. The two central concepts embodied in the SPA stomatal model, that plants account for both water-use efficiency and for hydraulic safety in regulating stomatal conductance, imply a notion of optimal plant strategies and provide testable model hypotheses, rather than empirical descriptions of plant behavior.
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Tramontini, Sara, Johanna Döring, Marco Vitali, Alessandra Ferrandino, Manfred Stoll, and Claudio Lovisolo. "Soil water-holding capacity mediates hydraulic and hormonal signals of near-isohydric and near-anisohydric Vitis cultivars in potted grapevines." Functional Plant Biology 41, no. 11 (2014): 1119. http://dx.doi.org/10.1071/fp13263.
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Grapevine (Vitis vinifera L.) expresses different responses to water stress, depending not only on genotype, but also on the influence of vineyard growing conditions or seasonality. Our aim was to analyse the effects on drought response of two grapevine cultivars growing on two soils, one water draining (WD) containing sand 80% volume and the other water retaining (WR), with no sand. Under these two different water-holding capacities Syrah, displaying a near-anisohydric response to water stress, and Cabernet Sauvignon (on the contrary, near-isohydric) were submitted to water stress in a pot trial. Xylem embolism contributed to plant adaptation to soil water deprivation: in both cultivars during late phases of water stress, however, in Syrah, already at moderate early stress levels. By contrast, Syrah showed a less effective stomatal control of drought than Cabernet Sauvignon. The abscisic acid (ABA) influenced tightly the stomatal conductance of Cabernet Sauvignon on both pot soils. In the near-anisohydric variety Syrah an ABA-related stomatal closure was induced in WR soil to maintain high levels of water potential, showing that a soil-related hormonal root-to-shoot signal causing stomatal closure superimposes on the putatively variety-induced anisohydric response to water stress.
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Yang, Ting, Xuguang Xing, Yan Gao, and Xiaoyi Ma. "An Environmentally Friendly Soil Amendment for Enhancing Soil Water Availability in Drought-Prone Soils." Agronomy 12, no. 1 (January 6, 2022): 133. http://dx.doi.org/10.3390/agronomy12010133.
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Applying soil amendments plays a critical role in relieving water stress in arid and semiarid areas. The natural clay mineral attapulgite (ATP) can be utilized to adjust the balance of water and soil environment. In this study, we investigated four different particle size distribution typical soils in the Loess Plateau: (1) lou soil (LS), (2) dark loessial soil (DS), (3) cultivated loess soil (CS), (4) sandy soil (SS). Five ATP application rates (0, 1%, 2%, 3%, and 4%) were selected to test the effect of ATP on the soil water retention curve, soil saturated hydraulic conductivity, and soil structure. The results showed that applied ATP significantly increased the soil clay content, and the relative change of SS with 3% ATP applied increased by 53.7%. The field water holding capacity of LS, DS, CS, and SS with 3% ATP applied increased by 8.9%, 9.6%, 18.2%, and 45.0%, respectively. Although applied ATP reduced the saturated hydraulic conductivity, the values of CS and SS were opposite when the amount of ATP applied was >3%. The relative change in the amount of 0.25–1 mm soil water-stable aggregates of SS was 155.9% when 3% ATP was applied. Applied ATP can enhance soil water retention and soil stability, which may improve limited water use efficiency and relieve soil desiccation in arid and semiarid areas or similar hydrogeological areas.
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Říha, Jaromír, and Jan Jandora. "Pressure conditions in the hole erosion test." Canadian Geotechnical Journal 52, no. 1 (January 2015): 114–19. http://dx.doi.org/10.1139/cgj-2013-0474.
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The hole erosion test (HET) is used in the study of soil erosion in the case of what is known as “piping” when concentrated leaks occur. The HET enables the determination of soil erosion characteristics such as the critical shear stress along the pre-formed hole (pipe) and the coefficient of soil erosion. Normally, in the HET, the hydraulic gradient is determined from the difference between the piezometric heads measured at the inflow and outflow chambers (upstream and downstream of the soil specimen). Hydraulic analysis shows that such measurements ignore losses at the entrance and exit of the hole, causing the overestimation of the hydraulic gradient along the length of the hole, and thus the calculated shear stress. In this technical note, the results of preliminary analysis using the Bernoulli principle and of numerical study of the pressure conditions in the HET apparatus are shown. The turbulent flow in the HET apparatus was calculated using ANSYS commercial CFD (computational fluid dynamics) software. The analysis was performed for various hole entrance shapes. The conclusion of this note details the differences between traditionally determined hydraulic gradients and those numerically derived along the length of a hole.
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Chen, Sijie, Haiwen Yan, Wei Shao, Wenjun Yu, Lingna Wei, Zongji Yang, Ye Su, Guangyuan Kan, and Shaohui Luo. "Inverse Estimation of Soil Hydraulic Parameters in a Landslide Deposit Based on a DE-MC Approach." Water 14, no. 22 (November 15, 2022): 3693. http://dx.doi.org/10.3390/w14223693.
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Extreme rainfall is a common triggering factor of landslide disasters, for infiltration and pore water pressure propagation can reduce suction stress and shear strength at the slip surface. The subsurface hydrological model is an essential component in the early-warning system of rainfall-triggered landslides, whereas soil moisture and pore water pressure simulated by the Darcy–Richards equation could be significantly affected by uncertainties in soil hydraulic parameters. This study conducted an inverse analysis of in situ measured soil moisture in an earthquake-induced landslide deposit, and the soil hydraulic parameters were optimized with the Differential Evolution Markov chain Monte Carlo method (DE-MC). The DE-MC approach was initially validated with a synthetic numerical experiment to demonstrate its effectiveness in finding the true soil hydraulic parameters. Besides, the soil water characteristic curve (SWCC) and hydraulic conductivity function (HCF) described with optimized soil hydraulic parameter sets had similar shapes despite the fact that soil hydraulic parameters may be different. Such equifinality phenomenon in inversely estimated soil hydraulic parameters, however, did not affect the performance of simulated soil moisture dynamics in the synthetic numerical experiment. The application of DE-MC to a real case study of a landslide deposit also indicated satisfying model performance in terms of accurate match between the in situ measured soil moisture content and ensemble of simulations. In conclusion, based on the satisfying performance of simulated soil moisture and the posterior probability density function (PDF) of parameter sets, the DE-MC approach can significantly reduce uncertainties in specified prior soil hydraulic parameters. This study suggested the integration of the DE-MC approach with the Darcy–Richards equation for an accurate quantification of unsaturated soil hydrology, which can be an essential modeling strategy to support the early-warning of rainfall-triggered landslides.
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Abbaszadeh, Mohammad M., and Sandra L. Houston. "Influence of Soil Cracking on the Soil-Water Characteristic Curve of Clay Soil." Soils and Rocks 38, no. 1 (January 1, 2015): 49–58. http://dx.doi.org/10.28927/sr.381049.
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The hydraulic conductivity for unsaturated soil conditions is more difficult to estimate than for the saturated condition. In addition, as the soil transitions from intact to cracked, the difficulty in estimating the unsaturated hydraulic conductivity increases. One critical step in the determination of unsaturated flow hydraulic conductivity is the evaluation of the Soil-Water Characteristic Curve (SWCC). In this paper, a series of laboratory studies of direct measurements of cracked soil SWCCs is presented, including challenges associated with the control of very low suction levels associated with crack dewatering. An oedometer-type SWCC apparatus, capable of suction and net normal stress control, and volume change measurement, was used in these experimental studies. It is common that SWCCs are comprised of matric suction values below about 1500 kPa, and total suction values for suctions higher than about 1500 kPa (Fredlund et al., 2012). In this study, all measured or controlled suction values were less than 1500 kPa and obtained using the axis translation method, and the curve in the higher suction range was projected by forcing the SWCC through 106 kPa for completely dried conditions (Fredlund et al., 2012). Volume change corrections were made to the reported volumetric water contents, which is of particular importance when the soil under consideration undergoes volume change in response to wetting or drying. A technique for the determination of the SWCC for cracked clay soils is presented. Test results validated the fact that the SWCC of a cracked soil can be represented by a bimodal function due to the Air Entry Value (AEV) of the cracks being much lower than the AEV of the soil matrix. It was also found that differences between the SWCC for cracked and intact soil appears only in the very low suction range.
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Chien, L. K., and Y. N. Oh. "Influence of fines content and initial shear stress on dynamic properties of hydraulic reclaimed soil." Canadian Geotechnical Journal 39, no. 1 (February 1, 2002): 242–53. http://dx.doi.org/10.1139/t01-082.
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The hydraulic placement of sand fill is one of the most important methods of land reclamation. During the reclamation process, losses of fines in sand are induced by the transportation of soil which affects the dynamic properties of the soil materials. In this study, the reclaimed soil in the Yunlin area of Taiwan is adopted as the test material. Different fines contents, different relative densities, and initial stress ratio were taken as test conditions. Resonant column tests were performed to evaluate the shear modulus and damping ratio of the reclaimed soil under initial shear stress. The results show that the maximum shear modulus decreases as the fines content increases. The influences of initial shear stress are discussed. A prediction method for maximum shear modulus under different fines content and initial shear stress is proposed based on empirical equations obtained. The results can be helpful for land reclamation design and assessment.Key words: reclaimed soil, fines content, initial shear stress, dynamic properties.
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Filipović, Vilim, Thomas Weninger, Lana Filipović, Andreas Schwen, Keith L. Bristow, Sophie Zechmeister-Boltenstern, and Sonja Leitner. "Inverse estimation of soil hydraulic properties and water repellency following artificially induced drought stress." Journal of Hydrology and Hydromechanics 66, no. 2 (June 1, 2018): 170–80. http://dx.doi.org/10.2478/johh-2018-0002.
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AbstractGlobal climate change is projected to continue and result in prolonged and more intense droughts, which can increase soil water repellency (SWR). To be able to estimate the consequences of SWR on vadose zone hydrology, it is important to determine soil hydraulic properties (SHP). Sequential modeling using HYDRUS (2D/3D) was performed on an experimental field site with artificially imposed drought scenarios (moderately M and severely S stressed) and a control plot. First, inverse modeling was performed for SHP estimation based on water and ethanol infiltration experimental data, followed by model validation on one selected irrigation event. Finally, hillslope modeling was performed to assess water balance for 2014. Results suggest that prolonged dry periods can increase soil water repellency. Inverse modeling was successfully performed for infiltrating liquids, water and ethanol, withR2and model efficiency (E) values both > 0.9. SHP derived from the ethanol measurements showed large differences in van Genuchten-Mualem (VGM) parameters for the M and S plots compared to water infiltration experiments. SWR resulted in large saturated hydraulic conductivity (Ks) decrease on the M and S scenarios. After validation of SHP on water content measurements during a selected irrigation event, one year simulations (2014) showed that water repellency increases surface runoff in non-structured soils at hillslopes.
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Agbai, W. P., and M. T. Kosuowei. "Influence of land-use systems on hydraulic properties of soils in Yenagoa and Amassoma, Bayelsa State, Nigeria." International Journal of Environment 11, no. 1 (June 20, 2022): 23–45. http://dx.doi.org/10.3126/ije.v11i1.45838.
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This research aimed to determine the effect of different land-use systems on the matric potential, and hydraulic conductivity of the soils of Yenagoa and Amassoma communities. Soil samples were collected from four respective land-use types namely: Fallow land, Oil Palm Plantation, Plantain Plantation, and Virgin land. A total of 12 samples were bulked from three replicates at each land use type and were collected at depths of 0-15cm, 15-30cm, and 30-45cm respectively. The samples were taken to the laboratory to analyze their physical, chemical, and hydrological properties. The result showed that the different land use had a significant effect (P<0.05) on some soil physical, chemical, and hydraulic characteristics. The different land-use systems had a significant effect on the soil hydraulic conductivity with the highest in virgin (13.6 cm/hr) and lowest in the plantain plantation (7.6 cm/hr). The virgin land recorded the highest Soil Water Holding Capacity (SWHC) of 2.85 cm with a range of 1.55 – 2.85cm and Plant Available Water Capacity (PAWC) of 0.19 cm3cm-3, with a range of 0.10 - 0.19 cm3cm-3, while the plantain plantation recorded the lowest (1.55 cm and 0.10 cm3cm3). Based on the study, it is recommended that soils with high Plant Available Water Capacity (PAWC) and Soil Water Holding Capacity (SWHC) be used to cultivate crops that are non-tolerant to water stress while organic amendments are used on soils with low fertility.
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Barrientos-Sanhueza, Cesar, Danny Cargnino-Cisternas, Alvaro Díaz-Barrera, and Italo F. Cuneo. "Bacterial Alginate-Based Hydrogel Reduces Hydro-Mechanical Soil-Related Problems in Agriculture Facing Climate Change." Polymers 14, no. 5 (February 25, 2022): 922. http://dx.doi.org/10.3390/polym14050922.
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Agricultural systems are facing the negative impacts of erosion and water scarcity, directly impacting the hydro-mechanical behavior of soil aggregation. Several technologies have been proposed to reduce hydro-mechanical soil-related problems in agriculture. Biopolymer-based hydrogels have been reported to be a great tool to tackle these problems in soils. In this study, we investigated the hydro-mechanical behavior of different soils media treated with Ca-bacterial alginate hydrogel. We used an unconfined uniaxial compression test, aggregate stability test and hydraulic conductivity measurements to investigate the mechanical and hydraulic behavior of treated soils media. Our results from unconfined uniaxial compression test showed that yield stress (i.e., strength) increased in treated soils with higher kaolinite and water content (i.e., HCM3), compared with untreated coarse quartz sand (i.e., CM1). Furthermore, we found that temperature is an important factor in the gelation capacity of our hydrogel. At room temperature, HCM3 displayed the higher aggregate stability, almost 5.5-fold compared with treated coarse quartz sand (HCM1), while this differential response was not sustained at warm temperature. In general, the addition of different quantities of kaolinite decreased the saturated hydraulic conductivity for all treatments. Finally, bright field microscopy imaging represents the soil media matrix between sand and clay particles with Ca-bacterial alginate hydrogel that modify the hydro-mechanical behavior of different soils media. The results of this study could be helpful for the soil-related problems in agriculture facing the negative effects of climate change.
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Taha, Mazahir M. M., Cheng-Pei Feng, and Sara H. S. Ahmed. "Modification of Mechanical Properties of Expansive Soil from North China by Using Rice Husk Ash." Materials 14, no. 11 (May 24, 2021): 2789. http://dx.doi.org/10.3390/ma14112789.
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The construction of buildings on expansive soils poses considerable risk of damage or collapse due to soil shrinkage or swelling made likely by the remarkable degree compressibility and weak shear resistance of such soils. In this research, rice husk ash (RHA) was added to expansive soil samples in different quantities of 0%, 4%, 8%, 12%, and 16% by weight of soil to determine their effects on the plasticity index, compaction parameters, consolidation performance, and California bearing ratio (CBR)of clay soil. The results show that the use of RHA increases the effective stress and decreases the void ratio and coefficient of consolidation. Adding 16% RHA resulted in the greatest reduction in the hydraulic conductivity, void ratio, and coefficient of consolidation. The void ratio decreased from 0.96 to 0.93, consolidation coefficient decreased from 2.52 to 2.33 cm2/s, and hydraulic conductivity decreased from 1.12 to 0.80 cm/s. The addition of RHA improved the soil properties and coefficient of consolidation due to the high density and cohesiveness of RHA. The results of this study can be used to provide a suitable basis for the treatment of expansive soil to provide improved conditions for infrastructure construction.
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Shao, Longtan, Shixiong Wu, Xiaoxia Guo, and Tiande Wen. "One−Dimensional Seepage of Unsaturated Soil Based on Soil−Water Characteristic Curve." Processes 10, no. 12 (December 2, 2022): 2564. http://dx.doi.org/10.3390/pr10122564.
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The uneven pore water distribution in unsaturated soil will cause water movement, change the hydraulic and mechanical characteristics of soil, and then cause soil damage. Therefore, it is important to study the hydraulic characteristics of unsaturated soil. In this paper, the law of conservation of mass and Darcy’s law were used to analyze the unit soil after seepage to obtain a continuous equation. Combined with the soil-water characteristic curve (SWCC), the effect of matric suction and permeability coefficient of unsaturated soil on infiltration rate is substituted into the equation. Through the analysis of pore water stress of the unit soil, the function of the unsaturated permeability coefficient with the effective saturation degree is obtained, and the theoretical formula of the one-dimensional infiltration rate of unsaturated soil is derived. Compared with other models, this formula has fewer parameters and is easy to use.
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Hashemi, Amirhossein, and Melis Sutman. "Thermo-hydro-mechanical behaviour of partially saturated fine-grained soils in the context of energy geostructures." Soils and Rocks 45, no. 1 (February 18, 2022): 1–17. http://dx.doi.org/10.28927/sr.2022.076821.
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The multi-physical phenomena, particularly water content and temperature variations, governing the behaviour of soils should be considered in the design and analysis of the energy geostructures. Soil temperature and water content variations impose a significant risk on the stability and serviceability of existing and future geostructures. Although potential failure modes, impacts at a system scale, and the response of saturated soils to thermal loads are previously discussed, interpretation of the thermo-hydro-mechanical behaviour of partially saturated soils in the context of energy geostructures is not thoroughly investigated. In this regard, this paper brings together the experimental data from several laboratory investigations to attain a comprehensive understanding of the partially saturated fine-grained soils response under thermo-hydro-mechanical loading, which plays a vital role in the analysis of the soil behaviour and energy geostructures in contact with them. In this paper, the effect of thermal loading in different matric suctions and hydraulic loading at different temperatures on soil preconsolidation stress, water content variation, thermal and hydraulic conductivities, and compression indexes are studied. Furthermore, soil thermal deformation is studied in detail for different overconsolidation ratios and matric suctions.
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Yan, Guo Xin, Wei Wu, and De Jun Zhao. "Numerical Simulation of Seepage Field of Tailing Water Channel in Construction Period of Coupling Fields of Stress and Seepage." Advanced Materials Research 919-921 (April 2014): 1240–43. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.1240.
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On the basic of rock and soil mass mathematic model, with the boundary conditions of classic section, the seepage field in construction period is simulated. Some conclusions are drawn: the hydraulic gradient of the channel slope where the seepage spills out exceeds the allowable hydraulic gradient and some engineering measures are needed to avoid seepage damage; hydraulic gradient on rock base is less than the allowable hydraulic gradient and the seepage is safe.
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Barbour, S. L., and N. Yang. "A review of the influence of clay–brine interactions on the geotechnical properties of Ca-montmorillonitic clayey soils from western Canada." Canadian Geotechnical Journal 30, no. 6 (December 1, 1993): 920–34. http://dx.doi.org/10.1139/t93-090.
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Natural Ca-montmorillonite clay soils or engineered clay barriers in western Canada are often used to contain brine generated from the surface disposal of potash tailings or from drilling activities associated with the oil and gas industry. The performance of these barriers has ranged from excellent to poor. The influence of salt brines on the geotechnical properties of these soils has been recognized as a potentially important factor for some time. It has been well documented in the literature that the behavior of clayey soils is strongly influenced by physicochemical interactions between clay particles and pore-fluid chemistry; consequently, the properties of these soils are sensitive to changes in the electrolyte concentration of the pore fluid. An increase in the concentration of the pore fluid to the levels of a concentrated brine can cause significant changes in the geotechnical properties of the soil. In this paper, the impact of brine contamination on the geotechnical properties of two Ca-montmorillonitic clayey soils of glacial origin from western Canada is reviewed. The influence of clay–brine interactions on the index properties (liquid limit, plastic limit, plastic index, mineralogy, density, grain size, and compaction characteristics), mechanical properties (volume change and shear strength), and hydraulic properties (hydraulic conductivity) is described. A quantitative explanation for the changes that occur in the hydraulic and mechanical properties of these soils as a result of brine permeation is also provided. This explanation relates the changes in pore-fluid chemistry to changes in an effective physicochemical stress state. This approach may be used to predict the changes in hydraulic conductivity, volume, or shear strength of a clayey soil as a result of brine contamination. Key words : clay–brine interactions, diffuse double layer, hydraulic conductivity, soil structure, physicochemical.
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Savi, Tadeja, Maria Marin, Jessica Luglio, Francesco Petruzzellis, Sefan Mayr, and Andrea Nardini. "Leaf hydraulic vulnerability protects stem functionality under drought stress in Salvia officinalis." Functional Plant Biology 43, no. 4 (2016): 370. http://dx.doi.org/10.1071/fp15324.
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Functional coordination between leaf and stem hydraulics has been proposed as a key trait of drought-resistant plants. A balanced water transport efficiency and safety of different plant organs might be of particular importance for plant survival in the Mediterranean climate. We monitored seasonal changes of leaf and stem water relations of Salvia officinalis L. in order to highlight strategies adopted by this species to survive in harsh environmental conditions. During summer drought, the water potential dropped below the turgor loss point thus reducing water loss by transpiration, whereas the photosynthetic efficiency remained relatively high. Leaves lost their water transport efficiency earlier than stems, although in both plant organs P50 (water potential inducing 50% loss of hydraulic conductivity) indicated surprisingly high vulnerability when compared with other drought-tolerant species. The fast recovery of leaf turgor upon restoration of soil water availability suggests that the reduction of leaf hydraulic conductance is not only a consequence of vein embolism, but cell shrinkage and consequent increase of resistance in the extra-xylem pathway may play an important role. We conclude that the drought tolerance of S. officinalis arises at least partly as a consequence of vulnerability segmentation.
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Wu, Haohao, Congsheng Fu, Lingling Zhang, and Huawu Wu. "Elevated Wildfire and Ecosystem Carbon Loss Risks Due to Plant Hydraulic Stress Functions: A Global Modeling Perspective." Fire 5, no. 6 (November 5, 2022): 187. http://dx.doi.org/10.3390/fire5060187.
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Wildfire risks are increasing due to the atmospheric and vegetation aridity under global warming. Plant hydraulic stress (PHS) functions regulate water transport along the soil–plant–atmosphere continuum under water stress conditions, which probably results in shifts in ecosystem wildfire regimes. Currently, how the PHS functions affect wildfire occurrence and subsequently the ecosystem carbon cycle via carbon loss at a global scale remains unclear. Here, we conducted global simulations during 1850–2010 using Community Land Model version 5 with and without the PHS configuration and quantified the PHS-induced changes. From the global perspective, the PHS functions increased plant transpiration, induced hydraulic redistribution (HR) of soil water by root, and decreased soil moisture; then, the functions increased fire occurrence (count), fire induced carbon loss, and ecosystem net primary productivity by 72%, 49%, and 15%, respectively. Spatially, the PHS functions greatly promoted fire occurrence and the consequent carbon loss in circumboreal forests and tropical savannas; whereas, the fire occurrence was limitedly affected or even decreased in equatorial rainforests. The strong downward HR process in the humid rainforests transported rainwater into deep soil layers, and strict stomatal regulation of the tropical trees restricted transpiration increment under atmospheric aridity, both of which helped to buffer the rainforests against drought and thus decreased fire risk. In contrast, dry savannas showed substantial upward HR, which increased water loss via soil evaporation and transpiration of the grasses with shallow roots. The tree–grass competition for limited soil moisture in the savannas benefited soil evaporation, which could aggravate plant hydraulic failure and increase wildfire risk.
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Liu, Xue Yan, Da Jun Yuan, and Ming Jing Jiang. "Macro-Micro Analysis of Soil Failure Mechanism in Unloading Condition." Applied Mechanics and Materials 170-173 (May 2012): 1847–55. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.1847.
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Numerical tests are carried out to research mechanism of hydraulic fracturing. As well as that: reservoir storage leads to bending of the embankment dam because of water pressure, especially upright core wall when reservoir storing rapidly, and then bending leads to vertical stress unload. The macro and micro mechanism of soil fracturing in unloading condition are analyzed by the Distinct Element Method (DEM). The results indicate that: (1) Initial stage of specimen will lead to volume response of dilatancy in the unloading condition. Actually, volume response is expressed as dilatancy consistently with the low level confining pressure and is expressed as dilatancy then compression latterly with the high level confining pressure. It suggests that the unloading condition may be a factor for granular material cracks. Particularly, not only the unloading condition with low level confining pressure leads to cracks, but also it helps the cracks development. So we argue that: unload condition, such as reservoir storage is a factor for hydraulic fracturing in the embankment dams, especially in low level stress areas. (2)The strength of soil in the unloading condition decreases than the loading condition, which contributes to hydraulic fracturing.
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Anderson, S. H., D. K. Cassel, and R. W. Skaggs. "Influence of Spatially Variable Soil Hydraulic Properties on Predictions of Water Stress." Soil Science Society of America Journal 51, no. 1 (January 1987): 17–22. http://dx.doi.org/10.2136/sssaj1987.03615995005100010004x.
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Nouwakpo, Sayiro K., Chi-hua Huang, Laura Bowling, and Phillip Owens. "Impact of Vertical Hydraulic Gradient on Rill Erodibility and Critical Shear Stress." Soil Science Society of America Journal 74, no. 6 (November 2010): 1914–21. http://dx.doi.org/10.2136/sssaj2009.0096.
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Kang, Hyo Sub, and Yun Tae Kim. "Rheological properties of loose sands subjected to upward flow." Canadian Geotechnical Journal 54, no. 5 (May 2017): 664–73. http://dx.doi.org/10.1139/cgj-2016-0171.
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The objective of this study was to investigate the rheological properties of loose sands subjected to upward flow by using a vane-type rheometer that controlled upward flow in the loose sand specimens. Various hydraulic gradients (i.e., i = 0–2.0) were applied to loose sands. The rheological properties of the loose sands, such as yield stress and viscosity, were determined based on the Bingham and Herschel–Bulkley models. The experimental results showed that the flow behavior of loose sand samples exhibited a shear thickening when the Herschel–Bulkley model was applied (i.e., nondimensional flow index n > 1) and exhibited a Bingham-like within a limited shear rate range (i.e., 1∼30 1/s). The latter is clearly shown for a relatively high shear rate. As the hydraulic gradient was increased, the flow characteristics were close to the Bingham fluid. Yield stress showed a tendency to decrease linearly as hydraulic gradient was increased. However, the viscosity of the loose sands maintained a constant value irrespective of hydraulic gradient. The test results indicated that the pore fluid pressure resulting from upward flow in a soil sample affects yield stress, which contributes to the initiation of debris flow mobilization. As a result, it was possible to estimate the rheological properties of soil at the condition of liquefaction (critical hydraulic gradient), or initial occurrence of debris flow.
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Moffat, Ricardo, and R. Jonathan Fannin. "A hydromechanical relation governing internal stability of cohesionless soil." Canadian Geotechnical Journal 48, no. 3 (March 2011): 413–24. http://dx.doi.org/10.1139/t10-070.
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Results are presented from permeameter tests involving unidirectional seepage flow through reconstituted specimens of four widely graded cohesionless soils. The onset of instability is defined by a significant decrease in local hydraulic gradient over a relatively short period of time. The novel concept of a hydromechanical path in stress ([Formula: see text]) – gradient (ijk) space is proposed, which describes the response to seepage flow during testing and terminates at the value of critical hydraulic gradient. The path terminus establishes a hydromechanical boundary governing the onset of seepage-induced internal instability in one-dimensional flow. The boundary represents a failure envelope, which is different for each of the four soils tested. A ranking of seepage-induced instability for each soil, from most unstable to least unstable, is found similar, but not identical to, the susceptibility to internal instability determined from empirical analysis of the gradation shape.
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Siemens, Greg, and James A. Blatz. "Development of a hydraulic conductivity apparatus for bentonite soils." Canadian Geotechnical Journal 44, no. 8 (August 2007): 997–1005. http://dx.doi.org/10.1139/t07-025.
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Measurement and interpretation of hydraulic conductivity in porous media is a complicated process, and many laboratory apparatuses exist for different soil types and conditions. To use models for interpretation and prediction of hydraulic conductivity, accurate test measurements are required. A new hydraulic conductivity apparatus is presented that includes simultaneous control of volume and stress states. The apparatus includes the ability to automatically control volume to apply selected displacement boundary conditions while imposing radial flow conditions. The capabilities of the system are displayed using two selected hydraulic conductivity tests on an unsaturated sand–bentonite mixture, which is a swelling soil. Hydraulic conductivity on the order of 10−13 m/s was measured using the new system and compared closely with previously measured values using a similar material. Post-test measurements displayed internal water content, density, and saturation changes that occurred during testing.
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Rezaei, M., P. Seuntjens, I. Joris, W. Boënne, S. Van Hoey, P. Campling, and W. M. Cornelis. "Sensitivity of water stress in a two-layered sandy grassland soil to variations in groundwater depth and soil hydraulic parameters." Hydrology and Earth System Sciences Discussions 12, no. 7 (July 20, 2015): 6881–920. http://dx.doi.org/10.5194/hessd-12-6881-2015.
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Abstract. Monitoring and modeling tools may improve irrigation strategies in precision agriculture. We used non-invasive soil moisture monitoring, a crop growth and a soil hydrological model to predict soil-water content fluctuations and crop yield in a heterogeneous sandy grassland soil under supplementary irrigation. The sensitivity of the model to hydraulic parameters, water stress, crop yield and lower boundary conditions was assessed. Free drainage and incremental constant head conditions was implemented in a lower boundary sensitivity analysis. A time-dependent sensitivity analysis showed that changes in soil water content are mainly affected by the soil saturated hydraulic conductivity Ks and the Mualem-van Genuchten retention curve shape parameters n and α. Results further showed that different parameter optimization strategies (two-, three-, four- or six-parameter optimizations) did not affect the calculated water stress and water content as significantly as does the bottom boundary. For this case, a two-parameter scenario, where Ks was optimized for each layer under the condition of a constant groundwater depth at 135–140 cm, performed best. A larger yield reduction, and a larger number and longer duration of stress conditions occurred in the free drainage condition as compared to constant boundary conditions. Numerical results showed that optimal irrigation scheduling using the aforementioned water stress calculations can save up to 12–22 % irrigation water as compared to the current irrigation regime. This resulted in a yield increase of 4.5–6.5 %, simulated by crop growth model.
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Moffat, Ricardo, R. Jonathan Fannin, and Stephen J. Garner. "Spatial and temporal progression of internal erosion in cohesionless soil." Canadian Geotechnical Journal 48, no. 3 (March 2011): 399–412. http://dx.doi.org/10.1139/t10-071.
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Permeameter tests were performed on four widely graded cohesionless soils, to study their susceptibility to internal erosion. Test specimens were reconstituted as a saturated slurry, consolidated, and then subjected to multi-stage seepage flow under increasing hydraulic gradient. The occurrence of internal instability is described qualitatively, from visual observations through the wall of the permeameter during a test and from post-test observations; it is also described quantitatively, from change of hydraulic gradient within the specimen and from axial displacement during a test. The results provide a novel insight into the spatial and temporal progression of seepage-induced internal instability. This insight yields an improved characterization of suffusion and suffosion in cohesionless soils, the progression of which appears governed by a critical combination of hydraulic gradient and effective stress.
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Dumais, Simon, and Jean-Marie Konrad. "One-dimensional large-strain thaw consolidation using nonlinear effective stress – void ratio – hydraulic conductivity relationships." Canadian Geotechnical Journal 55, no. 3 (March 2018): 414–26. http://dx.doi.org/10.1139/cgj-2017-0221.
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A one-dimensional model for the consolidation of thawing soils is formulated in terms of large-strain consolidation and heat-transfer equations. The model integrates heat transfer due to conduction, phase change, and advection. The hydromechanical behaviour is modelled by large-strain consolidation theory. The equations are coupled in a moving boundary scheme developed in Lagrangian coordinates. Finite strains are allowed and nonlinear effective stress – void ratio – hydraulic conductivity relationships are proposed to characterize the thawing soil properties. Initial conditions and boundary conditions are presented with special consideration for the moving boundary condition at the thaw front developed in terms of large-strain consolidation. The proposed model is applied and compared with small-strain thaw consolidation theory in a theoretical working example of a thawing fine-grained soil sample. The modelling results are presented in terms of temperature, thaw penetration, settlements, void ratio, and excess pore-water pressures.
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Guo, Mingming, Zhuoxin Chen, Wenlong Wang, Tianchao Wang, Qianhua Shi, Hongliang Kang, Man Zhao, and Lanqian Feng. "Spatiotemporal changes in flow hydraulic characteristics and soil loss during gully headcut erosion under controlled conditions." Hydrology and Earth System Sciences 25, no. 8 (August 19, 2021): 4473–94. http://dx.doi.org/10.5194/hess-25-4473-2021.
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Abstract. The spatiotemporal changes in flow hydraulics and energy consumption and their associated soil erosion remain unclear during gully headcut retreat. A simulated scouring experiment was conducted on five headcut plots consisting of upstream area (UA), gully headwall (GH), and gully bed (GB) to elucidate the spatiotemporal changes in flow hydraulic, energy consumption, and soil loss during headcut erosion. The flow velocity at the brink of a headcut increased as a power function of time, whereas the jet velocity entry to the plunge pool and jet shear stress either logarithmically or linearly decreased over time. The jet properties were significantly affected by upstream flow discharge. The Reynolds number, runoff shear stress, and stream power of UA and GB increased as logarithmic or power functions of time, but the Froude number decreased logarithmically over time. The Reynolds number, shear stress, and stream power decreased by 56.0 %, 63.8 %, and 55.9 %, respectively, but the Froude number increased by 7.9 % when flow dropped from UA to GB. The accumulated energy consumption of UA, GH, and GB positions linearly increased with time. In total, 91.12 %–99.90 % of total flow energy was consumed during headcut erosion, of which the gully head accounted for 77.7 % of total energy dissipation, followed by UA (18.3 %), and GB (4.0 %). The soil loss rate of the “UA-GH-GB” system initially rose and then gradually declined and levelled off. The soil loss of UA and GH decreased logarithmically over time, whereas the GB was mainly characterized by sediment deposition. The proportion of soil loss at UA and GH is 11.5 % and 88.5 %, respectively, of which the proportion of deposited sediment on GB reached 3.8 %. The change in soil loss of UA, GH, and GB was significantly affected by flow hydraulic and jet properties. The critical energy consumption initiating soil erosion of UA, GH, and GB is 1.62, 5.79, and 1.64 J s−1, respectively. These results are helpful for deepening the understanding of gully erosion process and hydrodynamic mechanisms and can also provide a scientific basis for the construction of gully erosion model and the design of gully erosion prevention measures.
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Bonan, G. B., M. Williams, R. A. Fisher, and K. W. Oleson. "Modeling stomatal conductance in the Earth system: linking leaf water-use efficiency and water transport along the soil-plant-atmosphere continuum." Geoscientific Model Development Discussions 7, no. 3 (May 7, 2014): 3085–159. http://dx.doi.org/10.5194/gmdd-7-3085-2014.
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Abstract. The empirical Ball–Berry stomatal conductance model is commonly used in Earth system models to simulate biotic regulation of evapotranspiration. However, the dependence of stomatal conductance (gs) on vapor pressure deficit (Ds) and soil moisture must both be empirically parameterized. We evaluated the Ball–Berry model used in the Community Land Model version 4.5 (CLM4.5) and an alternative stomatal conductance model that links leaf gas exchange, plant hydraulic constraints, and the soil–plant–atmosphere continuum (SPA) to numerically optimize photosynthetic carbon gain per unit water loss while preventing leaf water potential dropping below a critical minimum level. We evaluated two alternative optimization algorithms: intrinsic water-use efficiency (Δ An/Δ gs, the marginal carbon gain of stomatal opening) and water-use efficiency (Δ An/Δ El, the marginal carbon gain of water loss). We implemented the stomatal models in a multi-layer plant canopy model, to resolve profiles of gas exchange, leaf water potential, and plant hydraulics within the canopy, and evaluated the simulations using: (1) leaf analyses; (2) canopy net radiation, sensible heat flux, latent heat flux, and gross primary production at six AmeriFlux sites spanning 51 site–years; and (3) parameter sensitivity analyses. Without soil moisture stress, the performance of the SPA stomatal conductance model was generally comparable to or somewhat better than the Ball–Berry model in flux tower simulations, but was significantly better than the Ball–Berry model when there was soil moisture stress. Functional dependence of gs on soil moisture emerged from the physiological theory linking leaf water-use efficiency and water flow to and from the leaf along the soil-to-leaf pathway rather than being imposed a priori, as in the Ball–Berry model. Similar functional dependence of gs on Ds emerged from the water-use efficiency optimization. Sensitivity analyses showed that two parameters (stomatal efficiency and root hydraulic conductivity) minimized errors with the SPA stomatal conductance model. The critical stomatal efficiency for optimization (ι) was estimated from leaf trait datasets and is related to the slope parameter (g1) of the Ball–Berry model. The optimized parameter value was consistent with this estimate. Optimized root hydraulic conductivity was consistent with estimates from literature surveys. The two central concepts embodied in the stomatal model, that plants account for both water-use efficiency and for hydraulic safety in regulating stomatal conductance, imply a notion of optimal plant strategies and provide testable model hypotheses, rather than empirical descriptions of plant behavior.