A model to predict the water retention curve from basic geotechnical properties

2003 ◽  
Vol 40 (6) ◽  
pp. 1104-1122 ◽  
Author(s):  
M Aubertin ◽  
M Mbonimpa ◽  
B Bussière ◽  
R P Chapuis
Keyword(s):  
Grain Size ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Liquid Limit ◽  
Geotechnical Properties ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Adhesion Forces ◽  
Retention Curve ◽  
Fine Grained

The water retention curve (WRC) has become a key material function to define the unsaturated behavior of soils and other particulate media. In many instances, it can be useful to have an estimate of the WRC early in a project, when little or no test results are available. Predictive models, based on easy to obtain geotechnical properties, can also be employed to evaluate how changing parameters (e.g., porosity or grain size) affect the WRC. In this paper, the authors present a general set of equations developed for predicting the relationship between volumetric water content, θ, (or the corresponding degree of saturation, Sr) and suction, ψ. The proposed model assumes that water retention results from the combined effect of capillary and adhesion forces. The complete set of equations is given together with complementary relationships developed for specific applications on granular materials and on fine-grained soils. It is shown that the model provides a simple and practical means to estimate the water retention curve from basic geotechnical properties. A discussion follows on the capabilities and limitations of the model, and on additional tools developed to complement its use. Key words: water retention curve, unsaturated soils, prediction, porosity, grain size, liquid limit.

Soil-water retention curve model for fine-grained soils accounting for void ratio-dependent capillarity

2021 ◽  
Author(s):  
Jiangu Qian ◽  
Zhiqiang Lin ◽  
Zhenhao Shi
Keyword(s):  
Volume Change ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Void Ratio ◽  
Water Retention Curve ◽  
Capillary Water ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Fine Grained

This paper presents a soil-water retention curve (SWRC) model for fine-grained soils. Compared with existing studies, the proposed model accounts for the distinct roles of the volume change of soils on capillarity and adsorption mechanisms. The capillary water is described by a relation that includes the characteristics of the pore-size distributions as parameters, while the absorbed water is modeled by a novel proposition that both considers the phenomenon of capillary condensation and allows for the decoupling between the degree of capillary and adsorptive saturation. Based on this feature, the void ratio effects are considered in a way in which they only affect capillary water, i.e., consistent with how volume change influences soil microstructures. The relative contributions of void ratio effects and hydraulic hysteresis on the path- and history-dependence of SWRC in Sr-s-e space for deformable unsaturated soils are examined. The significance of discriminating the effects of volume change on capillary and adsorptive water is illustrated by applying the SWRC model to computing the shear strength of unsaturated soils with different void ratios. The model performance is assessed by comparing against test data reported for four types of fine-grained soils and that tested for natural loess in this work.

Predicting the unsaturated hydraulic conductivity of granular soils from basic geotechnical properties using the modified Kovács (MK) model and statistical models

2006 ◽  
Vol 43 (8) ◽  
pp. 773-787 ◽  
Author(s):  
M Mbonimpa ◽  
M Aubertin ◽  
B Bussière
Keyword(s):  
Hydraulic Conductivity ◽  
Statistical Models ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Geotechnical Properties ◽  
Water Retention Curve ◽  
Granular Soils ◽  
Retention Curve ◽  
Unsaturated Hydraulic Conductivity ◽  
Preliminary Validation

The water retention curve (WRC) is often used to define the relative hydraulic conductivity, kr, of unsaturated soils. In this paper, the authors propose the use of the modified Kovács (MK) model, developed to predict the WRC using basic geotechnical properties, combined with some existing statistical models to estimate the kr function. The proposed equations are implemented in MATLAB®. After a preliminary validation based on comparisons with existing solutions, predictive results are presented for granular soils. These indicate a relatively good agreement with experimental results from drainage tests taken from the literature. A discussion follows on the advantages and limitations of the proposed approach.Key words: water retention curve, unsaturated hydraulic conductivity, predictive models, granular soils.

Bishop coefficients in elastic and plastic regimes of unsaturated soils

2020 ◽  
Author(s):  
Jean-Michel Pereira ◽  
Patrick Dangla
Keyword(s):  
Experimental Data ◽  
Effective Stress ◽  
Unsaturated Soils ◽  
Water Retention ◽  
The Other ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Retention Curve ◽  
Deformation Regime ◽  
Definition Of

<p>The definition of a suitable effective stress to model the behaviour of unsaturated soils has been questioned for decades. This issue is still a matter of debate in the community. Recently, Alonso et al. (2010) have shown that this coefficient might depend on the microstructure of the soil and that fine plastic soils are characterised by a Bishop coefficient tending to deviate from the commonly used assumption according to which it is equal to the degree of saturation. On the other hand, Coussy et al. (2010) have shown that this coefficient deviates from the latter assumption if the isodeformation of all pores is not satisfied. They also showed that the Bishop coefficient might be different in elastic and plastic regimes, respectively.</p><p>In this work, we take advantage of experimental data available in the literature covering, for each soil, both elastic and plastic regimes at various saturation states and including the water retention curve together with microstructure data. We conclude that the Bishop coefficient depends on the deformation regime and that, in particular, distinct values might be used depending whether the plastic regime is active or not.</p><p>References:<strong><br></strong></p><p>Alonso, E. E., Pereira, J. M., Vaunat, J., & Olivella, S. (2010). A microstructurally based effective stress for unsaturated soils. <em>Géotechnique</em>, <em>60</em>(12), 913–925. https://doi.org/10.1680/geot.8.P.002</p><p>Coussy, O., Pereira, J. M., & Vaunat, J. (2010). Revisiting the thermodynamics of hardening plasticity for unsaturated soils. <em>Computers and Geotechnics</em>, <em>37</em>(1–2), 207–215. https://doi.org/10.1016/j.compgeo.2009.09.003</p>

scholarly journals The influence of rates of drying and wetting on measurements of soil water retention curves

2020 ◽  
Vol 195 ◽  
pp. 03005
Author(s):  
Arash Azizi ◽  
Ashutosh Kumar ◽  
Mwajuma Ibrahim Lingwanda ◽  
David Geoffrey Toll
Keyword(s):  
Unsaturated Soils ◽  
Water Retention ◽  
Continuous Measurement ◽  
High Capacity ◽  
Water Retention Curve ◽  
Testing System ◽  
Soil Water Retention ◽  
Comprehensive Description ◽  
Retention Curve ◽  
Lower Saturation

The water retention curve is fundamental for a comprehensive description of the hydro-mechanical behaviour of unsaturated soils. The water retention testing system developed at Durham University allows direct and continuous measurement of suction using a high capacity tensiometer, water content determined from mass readings of a digital balance and measurements of volume change. The system was modified to accommodate an additional tensiometer to measure suction at the top besides the existing one at the bottom of the soil specimen. Soil specimens were subjected to drying and wetting following two procedures: discrete measurements carried out in stages to ensure equalisation and continuous measurement at different rates. All suctions measured during continuous and discrete measurements were very close at high saturation degrees. At lower saturation degrees, the suction values from the top and bottom of the specimen deviated from suctions observed in discrete measurements. This deviation in suction values was more evident in accelerated drying and wetting patterns. This can be explained by the fact that water permeability reduces with the decrease in saturation levels.

scholarly journals Evolution of the soil water retention curve based on plastic volumetric strain

2020 ◽  
Vol 195 ◽  
pp. 02016
Author(s):  
J. Kodikara ◽  
C. Jayasundara
Keyword(s):  
Soil Water ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Void Ratio ◽  
Volumetric Strain ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Plastic Volumetric Strain

The water retention behaviour of soil can be defined as the relationship between the degree of saturation (or water content) and suction at a constant temperature, which characterises the hydraulic behaviour of unsaturated soils, normally represented as the soil water retention curve (SWRC). The SWRC is commonly measured at nominal net stress by initially saturating a soil specimen and then subjecting it to drying and wetting paths, resulting in major drying and wetting curves. However, there is evidence that during these major drying and wetting paths and initial saturation, soil can undergo volumetric deformation with changes in void ratio, sometimes plastically. Therefore, for coupling the SWRC with mechanical behaviour, the dependency of SWRC on other state variables such as void ratio has been proposed. In this paper, an approach to defining SWRC for a particular plastic volumetric strain is presented within the generalised MPK model. The SWRC evolves as soil is subjected to wet/dry cycles, eventually approaching drying and wetting curves relevant to an environmentally-stabilised state. The performance of this model is demonstrated by the simulation of the loading/unloading/drying/wetting paths followed in a laboratory experiment. In addition, the evolution of the commonly-considered major drying and wetting curves is simulated, highlighting key features of the environmentally-stabilised line..

Experiments and interpretations on unsaturated hydraulic properties using water retention tests based on the membrane in Korea

2020 ◽  
Author(s):  
Seboong Oh ◽  
Sungjin Kim ◽  
Kwang Ik Son
Keyword(s):  
Unsaturated Soils ◽  
Hydraulic Properties ◽  
Water Retention ◽  
Void Ratio ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Huge Amount ◽  
Retention Curve ◽  
Hydraulic Behavior

<p>In unsaturated soils, the soil water retention curve (SWRC) is most important in the fundamental hydraulic properties. In order to measure SWRCs through an alternative method in Korea, high air entry disks were replaced by micro membranes. Micro membranes are thin in which the air entry value is around 100kPa. Tests with the membrane are fast to reduce the duration of infiltration through the high air entry disk.</p><p>The water retention curves using the membrane were compared with the data using high air entry disks from the volumetric pressure plate extractor and Tempe pressure cell for samples of various sites. As a result, the SWRCs using the membrane were very similar for most cases and the micro membrane was verified as a useful tool to measure SWRCs.</p><p>The unsaturated hydraulic behavior could be measured easily using the membrane than ceramic disks and the huge amount of data could have been obtained in Korea. Using DB of SWRCs, the hydraulic properties were interpreted based on the parameters of the van Genuchten SWRC model. The void ratio and density are correlated to SWRCs under the same classification soil.</p><p><strong>Acknowledgements</strong> This research is supported by grant from Korean NRF (2019R1A2C1003604) and MOE (79608), which are greatly appreciated.</p>

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