A Fractal Approach for Predicting Unsaturated Hydraulic Conductivity of Deformable Clay

Tao, Gaoliang; Zhu, Xueliang; Cai, Jingong; Xiao, Henglin; Chen, Qingsheng; Yin, Chen

doi:10.1155/2019/8013851

Cited by 12 publications

(9 citation statements)

References 48 publications

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“…10.1680/jgeot.19.p.058 Chen et al, 2019;Tao et al, 2019). Unsaturated permeability also can be determined using empirical formulations, macroscopic models, or statistical models involving SWRCs (Leong and Rahardjo, 1997;Patil and Singh, 2016).…”

Section: Introductionmentioning

confidence: 99%

Measurements of permeability of saturated and unsaturated soils

Pandey

Lynch²,

Sivakumar

et al. 2021

Géotechnique

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The management and engineering assessments of geotechnical assets within the national transportation inventory require an appropriate knowledge of permeability of saturated and unsaturated soils. Determination of the permeability of saturated soils can be carried out using direct measurements, whereas that of unsaturated soils is often made using indirect methods based on Soil Water Retention Curve (SWRC). In this study an attempt was made to develop a novel approach for measuring the saturated and unsaturated permeability of soils. The tests were conducted on 100mm diameter reconstituted and compacted samples of glacial till. Suctions were generated by circulating low humidity air through a slender sand column located at the centre of the samples. Measurements of suction were made by two tensiometers located radially at the base of the samples. The drying process was terminated when the observed suctions reached or approached the limiting capacity of the tensiometers (1500 kPa). Combinations of suction measurements and volumetric strains during the drying process were used to determine the permeability by adopting analytical solutions as applicable to a radial flow condition.

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Section: Introductionmentioning

confidence: 99%

Measurements of permeability of saturated and unsaturated soils

Pandey

Lynch²,

Sivakumar

et al. 2021

Géotechnique

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“…Therefore, it is reasonable to use simple mapping method to predict the permeability coefficient of unsaturated soil. Tao and Zhu [25] derive a fractal model of the relative permeability coefficient of unsaturated soil based on fractal theory and seepage theory. The expression is as follows:…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, this paper recommends first measuring the unsaturated relative permeability coefficient and SWCC of the soil before deformation and fitting the value of λ based on the measured data before deformation, that is the λ value after deformation. This paper takes the Touchet silt loam in the literature [23] as an example to compare and analyze the difference between the prediction method proposed by Tao and Zhu [25], and the predicted results are shown in Figure 7. As illustrated in Figure 7, the predicted values of the unsaturated relative permeability coefficient obtained using the simplified unified model are better to those obtained using the Tao and Zhu model and are more in line with the measured value.…”

Section: Discussionmentioning

confidence: 99%

Simple Graphical Prediction of Relative Permeability of Unsaturated Soils under Deformations

et al. 2021

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At present, there are only a few existing models that can be used to predict the relative permeability of unsaturated soil under deformations, and the calculation process is relatively complex. In order to fit the measured value of the relative permeability coefficient of unsaturated soil before deformation, this work employs the simplified unified model of the relative permeability coefficient of unsaturated soil, and it obtains the index λ before deformation of the soil. In addition, the value of index λ remains unchanged before and after deformation. Based on the actual measured value of the soil–water characteristic curve before deformation, the air-entry value prediction model is used to predict the air-entry value of soil with different initial void ratios. The relative permeability coefficient of unsaturated soil is then conveniently predicted using the graphical method in combination with the simplified unified model. The method is validated by using the test data of silt loam, sandy loam, and unconsoildated sand. The results show that the predicted results are consistent with the measured values. The prediction method in this paper is simple and overcomes the limitations associated with the determination of the index λ. It expands the application range of the unsaturated relative permeability coefficient model while improving the accuracy of predictions.

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“…Previous studies have shown that the expansion and contraction of soils will have a significant impact on the soil water retention curve (e.g., Chen, Chen, & Yang, 2020;Romero, Della Vecchia, & Jommi, 2011). Many models have also been proposed to describe the soil water retention curve and relative hydraulic conductivity for deformable soils (e.g., Chen et al, 2020;Hu, Chen, Liu, & Zhou, 2013;Huang, Barbour, & Fredlund, 1998;Tao et al, 2019). However, further investigations of the models for the soil water retention curve and relative hydraulic conductivity of deformable soils are beyond the scope of this study.…”

Section: Models For Comparisonmentioning

confidence: 99%

A modification to the van Genuchten model for improved prediction of relative hydraulic conductivity of unsaturated soils

Kuang

Jiao

Shan

et al. 2020

European J Soil Science

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Modelling of flow and transport in unsaturated soils requires information on two fundamental hydraulic properties: the soil water retention curve and relative hydraulic conductivity. A soil's relative hydraulic conductivity is frequently predicted from the soil water retention curve. The most widely used combination is the van Genuchten model for the soil water retention curve and the Mualem model for relative hydraulic conductivity (VGM). Previous studies show that the VGM model underestimates measured relative hydraulic conductivity for soils with fine textures; a sharp drop in relative hydraulic conductivity can be seen near saturation. A new modification of the van Genuchten soil water retention model is proposed with the aim of improving the agreement between predicted and measured relative hydraulic conductivity. The Brooks and Corey-Burdine model is used to predict relative hydraulic conductivity from the modified van Genuchten soil water retention curve (MVG-BCB). The modified model assumes independent m and n in the van Genuchten model but with constraints n > 2 and 0 < m < 1. The MVG-BCB model is evaluated by comparing calculated and measured data for 59 soils that have widely varying soil textures, ranging from sandstone to clay. The MVG-BCB model improves the agreement between calculated and measured data for both the soil water retention curve and relative hydraulic conductivity. The MVG-BCB model is closer to measured relative hydraulic conductivity data for most of the selected soils and the sharp drop near saturation is eliminated. Both the modified soil water retention curve and relative hydraulic conductivity functions are smooth curves and can easily be incorporated into vadose zone flow and transport modellings. Highlights• A new modification to the van Genuchten soil water retention model.• The model improves the fit to measured soil water retention data.• The chosen model improves the prediction of relative hydraulic conductivity.

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A Fractal Approach for Predicting Unsaturated Hydraulic Conductivity of Deformable Clay

Cited by 12 publications

References 48 publications

Measurements of permeability of saturated and unsaturated soils

Measurements of permeability of saturated and unsaturated soils

Simple Graphical Prediction of Relative Permeability of Unsaturated Soils under Deformations

A modification to the van Genuchten model for improved prediction of relative hydraulic conductivity of unsaturated soils

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