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Compaction
Published in Bernardo Caicedo, Geotechnics of Roads, 2021
The water retention curve of a soil evolves during compaction because the sizes of the pores change. Several models have been proposed to describe the evolution of the water retention curve for soils undergoing compaction. Examples of this book use Equation 3.11, which was proposed in Ref. [34]: Sr={11+[ϕWseψW]nW}mW,
Water and Solute Transport and Storage
Published in L.G. Wilson, Lorne G. Everett, Stephen J. Cullen, Handbook of Vadose Zone Characterization & Monitoring, 2018
In unsaturated soils, the hydraulic conductivity decreases sharply with decreasing water content. This is because as soil loses water (drains) pores empty, and the cross sectional area for flow decreases. Thus, for soils that drain rapidly such as sands, the hydraulic conductivity decreases much more sharply with decreasing water content than for clay soils in which there are more intermediate size pores. These drain more slowly, and thus the hydraulic conductivity of clay soils decreases less sharply with decreasing water content. An example of changes in hydraulic conductivity with tension for the two soils of Table 4.2 is shown in Figure 4.3. Because water content is related to soil-water tension through the soil-water retention curve (Figure 4.1), the hydraulic conductivity is often shown as a function of soil-water tension. Note the exponential decrease in hydraulic conductivity with increasing tension.
Inverse analysis of in situ permeability test data for determining unsaturated soil hydraulic properties
Published in H. Rahardjo, D.G. Toll, E.C. Leong, Unsaturated Soils for Asia, 2020
Y. Takeshita, K. Yagi, T. Morii, M. Inoue
Knowledge of the unsaturated soil hydraulic properties is essential for prediction of seepage flow and contaminant transport through the vadose zone. These properties consist of the hydraulic conductivity as a function of pressure head and the soil water retention curve. Traditionally, steady state experiments have been used to estimate these properties. Recently, transient methods are becoming more popular. Transient experimental methods are inherently faster, because more powerful computers and seepage flow simulation technique are now available. The estimation of the hydraulic properties by using inverse methods can be performed easily.
Evaluation of the degree of saturation using Skempton coefficient B
Published in Geomechanics and Geoengineering, 2020
Mathilde Vernay, Mathilde Morvan, Pierre Breul
Suction value is linked to Sr by the water retention curve. Choosing the Brooks and Corey equation (Brooks and Corey 1964), as presented in Equation (20), two main parameters are considered: the air entry suction se that depends on grain size distribution and a soil parameter α that depends on grain size distribution uniformity. These two parameters vary with the type of soil and govern the water retention curve.