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

Canadian Geotechnical Journal ◽

10.1139/cgj-2021-0042 ◽

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.

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

E3S Web of Conferences ◽

10.1051/e3sconf/202019502016 ◽

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..

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

10.5194/egusphere-egu2020-3817 ◽

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

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.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.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.Acknowledgements This research is supported by grant from Korean NRF (2019R1A2C1003604) and MOE (79608), which are greatly appreciated.

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