Application of the Groenevelt - Grant soil water retention model to predict the hydraulic conductivity

We outline several formulations of the Groenevelt–Grant water retention model of 2004 to show how it can be anchored at different points. The model is highly flexible and easy to perform multiple differentiations and integrations on. Among many possible formulations of the model we choose one anchored solely at the saturated water content, θs, to facilitate comparison with the van Genuchten model of 1980 and to obtain a hydraulic conductivity function through analytical integration: where, k0, k1, and n are fitting parameters. We divided this formulation by θs to obtain the relative water content, θr(h), and inverted the function to produce a form required for integration, namely: in which the parameter β is introduced to accommodate both the ‘Burdine’ and ‘Mualem’ models. The integrals are identified as incomplete gamma functions and are distinctly different from the incomplete beta functions embodied in the van Genuchten–Mualem models. Rijtema’s data from 1969 for 20 Dutch soils are used to demonstrate the procedures involved. The water retention curves produced by our Groenevelt–Grant model are virtually indistinguishable from those produced by the van Genuchten model. Relative hydraulic conductivities produced by our Mualem and Burdine models produced closer estimates of Rijtema’s measured values than those produced by the van Genuchten–Mualem model for 19 of his 20 soils. This work provides an alternative to the widely used van Genuchten–Mualem approach and represents a preamble for the, as yet unsatisfactory, treatment of the tortuosity component of the unsaturated hydraulic conductivity function.

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On the Improvement of Hydraulic Conductivity Function in Van Genuchten-Mualem Model

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.513-517.4417 ◽

2014 ◽

Vol 513-517 ◽

pp. 4417-4420 ◽

Cited By ~ 2

Author(s):

Yeong Mog Park ◽

Seboong Oh ◽

Inchul Jin ◽

Kyun Kwon Oh

Keyword(s):

Hydraulic Conductivity ◽

Unsaturated Soils ◽

Water Retention ◽

Rapid Change ◽

Model Fit ◽

Soil Water Retention ◽

Rapid Reduction ◽

Integration Interval ◽

Van Genuchten Model ◽

Conductivity Function

Hydraulic conductivity (HC) is deduced indirectly from soil water retention curves (SWRC) by Mualem model, but the mathematical calculation in the Mualem model is sensitive to integration interval near saturation. After the van Genuchten model fit actual SWRC, the van Genuchten-Mualem (VGM) HC is integrated simply by an analytical function for unsaturated soils. However the analytical solution on VGM HC results in the rapid change of HC near saturation. For unsaturated soils sampled in Korea, SWRCs and unsaturated HCs were obtained by experiments. The HC experiments were compared with the HC models from the SWRCs. As a result, VGM models of HC function underestimate the unsaturated HC and show rapid reduction near saturation. It is found that a modification in VGM model should be required to predict accurate HC functions.

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A numerical study on the effect of salinity on stability of an unsaturated railway embankment under rainfall

E3S Web of Conferences ◽

10.1051/e3sconf/202019501004 ◽

2020 ◽

Vol 195 ◽

pp. 01004

Author(s):

Ali Kolahdooz ◽

Hamed Sadeghi ◽

Mohammad Mehdi Ahmadi

Keyword(s):

Hydraulic Conductivity ◽

Soil Water ◽

Water Retention ◽

Numerical Study ◽

Water Retention Curve ◽

Soil Water Retention Curve ◽

Soil Water Retention ◽

Unsaturated Hydraulic Conductivity ◽

Influence Of Water ◽

Dispersive Soils

Dispersive soils, as one of the main categories of problematic soils, can be found in some parts of the earth, such as the eastern-south of Iran, nearby the Gulf of Oman. One of the most important factors enhancing the dispersive potential is the existence of dissolved salts in the soil water. The main objective of this study is to explore the influence of water salinity on the instability of a railway embankment due to rainfall infiltration. In order to achieve this goal, the embankment resting on a dispersive stratum is numerically modeled and subjected to transient infiltration flow. The effect of dispersion is simplified through variations in the soil-water retention curve with salinity. The measured water retention curves revealed that by omitting the natural salinity in the soil-water, the retention capability of the soil decreases; therefore, the unsaturated hydraulic conductivity of the soil stratum will significantly decline. According to the extensive decrease in the hydraulic conductivity of the desalinated materials, the rainfall cannot infiltrate in the embankment and the rainfall mostly runs off. However, in the saline embankment, the infiltration decreases the soil suction; and consequently, the factor of safety of the railway embankment decreases.

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Simultaneous scaling of soil water retention and unsaturated hydraulic conductivity functions assuming lognormal pore-size distribution

Advances in Water Resources ◽

10.1016/s0309-1708(00)00070-1 ◽

2001 ◽

Vol 24 (6) ◽

pp. 677-688 ◽

Cited By ~ 49

Author(s):

A. Tuli ◽

K. Kosugi ◽

J.W. Hopmans

Keyword(s):

Hydraulic Conductivity ◽

Pore Size Distribution ◽

Pore Size ◽

Size Distribution ◽

Soil Water ◽

Water Retention ◽

Soil Water Retention ◽

Unsaturated Hydraulic Conductivity

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Finite formulation for the computation of sorptivity

10.5194/egusphere-egu2020-22664 ◽

2020 ◽

Author(s):

Pierre-Emmanuel Peyneau ◽

Laurent Lassabatere ◽

Joseph Pollacco ◽

Jesús Fernández-Gálvez ◽

Borja Latorre ◽

...

Keyword(s):

Hydraulic Conductivity ◽

Water Content ◽

Water Retention ◽

Water Pressure ◽

Pressure Head ◽

Concentration Function ◽

Point Of View ◽

Water Infiltration ◽

Unsaturated Hydraulic Conductivity ◽

Flux Concentration

<p>Soil sorptivity is one of the key hydraulic parameters for modelling water infiltration into soil. It quantifies the capacity of a soil to infiltrate water by capillarity. Several formulations, based on various models, have been proposed to compute it from the water retention and the unsaturated hydraulic conductivity functions. All these formulations use the integration of the product of either the hydraulic conductivity or diffusivity function with the flux concentration function. The integration can be performed either over an interval of water pressure head or water content, yielding two equal values. However, the expression of the integral as a function of water pressure head may involve a huge or even infinite interval, which can be numerically difficult to handle. In opposite, the expression of the integral as a function of water content involves the integration of a diverging function (diffusivity) over a large interval, which is also troublesome from a numerical point of view. In this paper, we provide a new expression for sorptivity by cutting the integral in two parts, in order to involve only the integration of a finite function over a finite interval. The dependency of the integral on the flux concentration function is also investigated.</p>

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A study on the geotechnical characterization and water retention characteristic curve of pond ash

Water Science & Technology ◽

10.2166/wst.2019.334 ◽

2019 ◽

Vol 80 (5) ◽

pp. 929-938

Author(s):

Janmeet Singh ◽

Sanjay Kumar Singh ◽

M. A. Alam

Keyword(s):

Hydraulic Conductivity ◽

Water Retention ◽

Characteristic Curve ◽

Input Parameter ◽

Wetting And Drying ◽

Pond Ash ◽

Retention Characteristic ◽

Unsaturated Hydraulic Conductivity ◽

Conductivity Function ◽

Engineering Practices

Abstract The understanding of the engineering behaviour of unsaturated soil is totally dependent on the water retention characteristic curve (WRCC). In this paper, a comprehensive study of the WRCCs of pond ash along with the ash's geotechnical behaviour has been made. The WRCC has been drawn experimentally using a Fredlund device based upon the pressure plate technique for both wetting and drying cycles. Further, an investigation was carried out to study WRCC hysteresis of pond ash. There exists a considerable hysteresis in drying and wetting curves of pond ash sample. The different WRCC models were used to fit the experimental WRCC data. The effect of compaction on WRCC was also studied. The air entry value in the case of a loose sample is low and the sample gets nearly desaturated at low soil suction as compared to a dense sample. Also, the wetting WRCC is predicted using the Feng and Fredlund model as it is difficult and time consuming to measure the whole hysteresis. The predicted results are compared with the measured wetting WRCC. Since the direct measurement of unsaturated hydraulic conductivity is difficult to obtain in engineering practices, the unsaturated hydraulic conductivity function is predicted using the measured WRCC as the input parameter using SEEP/W software.

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Effect of Unimodal and Bimodal Soil Hydraulic Properties on Slope Stability Analysis

Water ◽

10.3390/w13121674 ◽

2021 ◽

Vol 13 (12) ◽

pp. 1674

Author(s):

Hsin-Fu Yeh ◽

Tsien-Ting Huang ◽

Jhe-Wei Lee

Keyword(s):

Hydraulic Conductivity ◽

Slope Stability ◽

Water Content ◽

Water Retention ◽

Water Retention Capacity ◽

Retention Capacity ◽

Seepage Analysis ◽

Hydraulic Behavior ◽

Conductivity Function ◽

The Impact

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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