Coupled water retention and shrinkage properties of a compacted silt under isotropic and deviatoric stress paths

2012 ◽  
Vol 49 (8) ◽  
pp. 928-938 ◽  
Author(s):  
C.F. Chiu ◽  
Charles W.W. Ng
Keyword(s):  
Hysteresis Loop ◽  
Unsaturated Soil ◽  
Water Retention ◽  
Stress Path ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Mean Stress ◽  
Test Results ◽  
Retention Curve ◽  
Shrinkage Curve

Although it is generally recognized that unsaturated soil behavior is governed by two constitutive variables (matric suction and net normal stress) and that the hydromechanical behavior of unsaturated soil is coupled, a water retention curve obtained from tests under zero stress and assuming no volume change is still fairly common. A relatively limited number of studies on the stress path–dependent water retention curve (SDWRC), particularly under a broader range of stress paths, exist in the literature. In this paper, the SDWRC, shrinkage curve, and swelling curve of a compacted silt subjected to isotropic and deviatoric stress paths are presented. The test results show that the air-entry value (AEV) increases, but the hydraulic hysteresis loop decreases with an increase in net mean stress. Furthermore, for a given stress level, the K0-compressed specimen exhibits higher AEV, but a smaller hysteresis loop than that of the isotropically compressed specimen. A nonlinear shrinkage curve is observed and the gradient of the post-yield shrinkage curve depends on the degree of saturation and net mean stress, but is independent of the stress path. For the range of suction studied, the gradient reduces with a decreasing degree of saturation, but with an increasing net mean stress. Finally, the test results are compared with the prediction of a model based on two independent constitutive stress variables.

scholarly journals Investigating the effect of porosity on the soil water retention curve using the multiphase Lattice Boltzmann Method

2021 ◽  
Vol 249 ◽  
pp. 09007
Author(s):  
Reihaneh Hosseini ◽  
Krishna Kumar ◽  
Jean-Yves Delenne
Keyword(s):  
Lattice Boltzmann Method ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Lattice Boltzmann ◽  
Water Retention ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Boltzmann Method

The soil water retention curve (SWRC) is the most commonly used relationship in the study of unsaturated soil. In this paper, the effect of porosity on the SWRC is investigated by numerically modeling unsaturated soil using the Shan-Chen multiphase Lattice Boltzmann Method. The shape of simulated SWRCs are compared against that predicted by the van Genuchten model, demonstrating a good fit except at low degrees of saturation. The simulated SWRCs show an increase in the air-entry value as porosity decreases.

scholarly journals Hydromechanical behaviour of a silty sand from a steep slope triggered by artificial rainfall: from unsaturated to saturated conditions

2013 ◽  
Vol 50 (1) ◽  
pp. 28-40 ◽  
Author(s):  
Francesca Casini ◽  
Victor Serri ◽  
Sarah M. Springman
Keyword(s):  
Mechanical Behaviour ◽  
Water Retention ◽  
Stress Path ◽  
Steep Slope ◽  
Silty Sand ◽  
Water Retention Curve ◽  
Retention Curve ◽  
Hydromechanical Behaviour ◽  
Water Contents

This paper presents an experimental investigation aimed at studying the hydromechanical behaviour of a silty sand from a steep slope in Ruedlingen in the northeast of Switzerland, where a landslide-triggering experiment was carried out. The hydromechanical behaviour of the statically compacted Ruedlingen silty sand has been studied under saturated and unsaturated conditions, beginning with different initial void ratios and water contents. The specimens were prepared in the laboratory using static compaction, to reproduce the mean dry density and mean water content expected in natural unsaturated in situ conditions, thus promoting specimen homogeneity and test repeatability. The choice of compaction parameters was supported by a detailed physical and microstructural investigation to produce laboratory specimens with a similar microstructure to that of the natural soil. The aim of the work was to characterize the mechanical behaviour of the soil at different gravimetric water contents in a triaxial stress path apparatus and to link the mechanical behaviour with the soil-water retention curve obtained under suction-controlled conditions with different void ratios. Soil specimens with three different gravimetric water contents were exposed to conventional isotropically consolidated drained and undrained stress paths for the water phase and to stress paths simulating in situ anisotropic compression followed by a decrease of mean effective stress at constant axial load. The radial deformation of the unsaturated specimens was measured with a laser device installed in a triaxial stress path cell. Results have been interpreted using a Bishop stress approach, evaluating the suction through the water retention curve. A simple equation has been proposed to model the compressibility behaviour of the soil tested, which depends on the parameter χ and the stress ratio η. Possible unstable response along the stress path analysed has been investigated by means of second-order work and the validity of a unified framework has also been verified under unsaturated conditions.

Water retention and volumetric characteristics of intact and re-compacted loess

2016 ◽  
Vol 53 (8) ◽  
pp. 1258-1269 ◽  
Author(s):  
Charles Wang Wai Ng ◽  
Hamed Sadeghi ◽  
S.K. Belal Hossen ◽  
C.F. Chiu ◽  
Eduardo E. Alonso ◽  
...  
Keyword(s):  
Volume Change ◽  
Water Retention ◽  
Water Retention Curve ◽  
Test Results ◽  
Retention Curve ◽  
Vapor Equilibrium ◽  
Wetting Curve ◽  
Stress Dependent ◽  
Compacted Loess ◽  
Intact Loess

A laboratory testing program was conducted to investigate the effects of microstructure on the water retention curve (WRC) and wetting–drying induced volume change in loess. The axis translation and vapor equilibrium techniques were adopted to control suction in the range of 0–400 kPa and 4–140 MPa, respectively. Hysteresis in the WRC of loess was observed for the entire range of suction studied. Compared to re-compacted loess, intact loess exhibits a more pronounced hysteresis in the suction range below 20 kPa, which can be explained by the ink-bottle pore neck effect or constricted pores. The hypothesis is supported by microstructural evidence of mercury intrusion porosimetry and scanning electron microscopy tests. However, re-compacted loess exhibits larger hysteresis than intact loess for suctions above 30 kPa. A conceptual model was introduced, which links WRC to the corresponding pore-size density (PSD) function. Regarding volume change, more noticeable drying-induced shrinkage, but yielding at a lower suction, was observed for re-compacted loess. This is consistent with the compression test results. Stress has a significant effect on change of PSD and constricted macropores leading to a shift in the main wetting curve and a less pronounced hysteresis. Intact loess exhibits a stress-dependent wetting-induced collapse and drying-induced shrinkage.

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.

scholarly journals Experimental Study And Modeling Of Water Retention Curve Of A Silty Soil Compacted And Treated With Cement

2020 ◽  
Vol 9 (3) ◽  
pp. 157-176
Author(s):  
Belal Tewfik ◽  
Ghembaza Moulay Smaine ◽  
Bellia Zoheir
Keyword(s):  
Soil Water ◽  
Water Retention ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Experimental Measurements ◽  
Characteristic Curves ◽  
Retention Curve ◽  
Treated Soil ◽  
Water Behavior ◽  
Soil Water Characteristic Curves

The evaluation of unsaturated soils' fundamental properties is ensured by the characteristic water retention curve for a wide range of soil suction values. However, a minimal number of research works have focused on studying the water retention properties of natural soils and treated with hydraulic binders using soil-water characteristic curves (SWCC). The present work is motivated by the lack of experimental evidence of this type. Firstly, experimental measurements of soil-water characteristic curves of a natural loam soil from the region of Sidi Bel Abbes (Algeria), treated with cement and compacted at Standard Optimum Proctor at an ambient temperature of 20 °C, Were carried out using the methods of the imposition of suction, namely the osmotic method ranging from 0 to 0.05 MPa and the method of saline solutions over a suction range from 0.05 MPa to about 343 MPa respectively. The suction used were applied to four studied mixtures (natural soil, + 2%, + 4% and + 6% cement). At the end of the tests on the drainage-humidification path, the water retention curves for the treated soil at different cement dosage allow us to determine the different state parameters of the treated soil: Degree of saturation (Sr), dry weight (d), void ratio (e) and water content (w). The suction imposition range and the cement dosage significantly influence the water behavior of the material studied. On the other hand, we develop a model of the water behavior of soils treated with cement. This model makes it possible to correctly predict the retention curves at different cement dosage from the experimental measurements performed on samples compacted at Standard Optimum Proctor represented in the plans [suction, degree of saturation] and [suction, moisture content].

Estimation of the water retention curve for unsaturated clay

2011 ◽  
Vol 91 (4) ◽  
pp. 543-549 ◽  
Author(s):  
Seid Majdeddin Mir Mohammad Hosseini ◽  
Navid Ganjian ◽  
Yadolah Pashang Pisheh
Keyword(s):  
Soil Properties ◽  
Soil Water ◽  
Unsaturated Soil ◽  
Laboratory Tests ◽  
Water Retention ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Retention Curve ◽  
Unsaturated Clay

Mir Mohammad Hosseini, S. M., Ganjian, N. and Pashang Pisheh, Y. 2011. Estimation of the water retention curve for unsaturated clay. Can. J. Soil Sci. 91: 543–549. Extensive laboratory tests are essential in order to determine the soil water retention curve, defined as the relationship between water content and suction, in an unsaturated soil. These laboratory tests are usually costly and time consuming. Moreover, for most practical problems, it has been found that approximate unsaturated soil properties are adequate for analysis. Thus, empirical procedures for predicting unsaturated soil parameters would be invaluable. The water retention curve can be estimated using soil properties to avoid the costs of experimental methods. Estimation of the water retention curve based on index properties is highly desirable due to its simplicity and low cost. Here, a model for the estimation of the soil water retention curve for fine soils is introduced, which takes the plasticity index and fine content into account, and is based on the Van Genuchten and Fredlund-Xing equations. The proposed equations are validated by comparing measured and simulated results. The curves predicted with these models were found to be in good agreement with the experimental results.

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