The role of pore water in the mechanical behavior of unsaturated soils

Karube, Daizo; Kawai, Katsuyuki

doi:10.1007/978-94-015-9775-3_2

Cited by 41 publications

(43 citation statements)

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“…Most of the previous work related to tensile strength of the unsaturated soils has been limited to fine-grained soils, such as clay or clayey silt, or cemented fine-grained soils (Bishop and Garga 1969;Bofinger 1970;Al-Hussaini and Townsend 1973 and others). Only in the past few decades, advances have been made on the qualitative and quantitative understanding of the capillary attraction mechanism in unsaturated granular materials (Rumpf 1961;Schubert et al 1975aSchubert et al , 1975bOrr et al 1975;Dobbs and Yeomans 1992;Pierrat and Caram 1997;Kim 2001;Karube and Kawai 2001;Kim and Hwang 2003;Kim and Sture 2004;Molenkamp and Nazemi 2003;Lu et al, 2007).…”

Section: Problem Statementmentioning

confidence: 99%

Effect of Pore-Water Surface Tension on Tensile Strength of Unsaturated Sand

2016

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Tensile behaviour of unsaturated sand was investigated both experimentally and theoretically.A custom-built direct tension apparatus was employed to perform direct tension tests on unsaturated silica sand specimens at different saturations levels and packing dry densities.Attempt was made to understand the effect of surface tension of pore-liquid and tensile loading rate on the tensile strength. It was found that the tensile strength decreases, as the surface tension of the pore-liquid decreases and rate of loading increases. However, tensile strength does not decrease as a simple multiple of ratio of surface tension of pore-liquid. The experimental results were also compared with the predicted results from two theoretical tensile strength models, namely, micro-mechanical and the macro-mechanical models. Results predicted using the micro-mechanical model agreed well with the experimental results, but only for specimens containing distilled water in the pendular saturation regime. On the other hand, the macro-mechanical model followed the experimental trend across pendular and funicular saturation regimes for specimens containing distilled water reasonably well.However, at reduced surface tension of pore-liquid, both models significantly under-predicted the experimental tensile strength results.iii ACKNOWLEDGEMENTS Foremost, I would like to express the deepest appreciation to my thesis supervisor and mentor, Dr. Jitendrapal Sharma, who has the attitude and the substance of a genius. Without his guidance and relentless encouragement, my thesis would not have been possible. I would also like to thank him for his financial support throughout the course of the researchwork.Thanks for everything, Dr. Sharma.In addition, a big thank you to my co-supervisor Dr. Rashid Bashir, whose expertise in unsaturated soil mechanics helped me to structure my research and thesis. He has shared valuable insights in the relevance of the study and made this research successful. I would also

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Section: Problem Statementmentioning

confidence: 99%

Effect of Pore-Water Surface Tension on Tensile Strength of Unsaturated Sand

2016

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“…One major characteristic of unsaturated soils is the soil water retention curve (SWRC), which specifies capillary pressure value associated with the water saturation degree. In recent years, experimental evidences have clearly shown that soil water retention curves are dependent on the stress level (Romero and Vaunat 2000;Karube and Kawai 2001;Gallipoli et al 2003b;Tarantino and Tombolato 2005;Nuth and Laloui 2008;Tarantino 2009;Uchaipichat 2010). Tarantino (2009) has considered the dependency of air entry value on stress level and has offered a SWRC equation for deformable media.…”

Section: Introductionmentioning

confidence: 99%

Bridging Effective Stress and Soil Water Retention Equations in Deforming Unsaturated Porous Media: A Thermodynamic Approach

2017

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The finite deformation of an unsaturated porous medium is analysed from first principles of mixture theory. An expression for Bishop's effective stress is derived from (1) the deformation-dependent Brooks and Corey's water retention curve and (2) the restrictions on the constitutive relationships of an unsaturated medium subject to finite deformation. The resulting expression for the effective stress parameter χ is reasonably consistent with experimental data from the literature. Hence, it is shown that Bishop's equation is constitutively linked to water retention curves in deforming media.Keywords Porous medium · Wetting fluid · Non-wetting fluid · Saturation List of symbols

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“…Therefore it is not surprising that constitutive models that use only suction as the unsaturated variable face difficulties in describing important features of unsaturated soil behaviour. Another class of elasto-plastic models for unsaturated soils, such as those proposed by Jommi & Di Prisco (1994), Bolzon et al (1996), Loret & Khalili (2000) and Karube & Kawai (2001), are expressed in terms of a different set of constitutive variables that explicitly include the degree of saturation in their definitions. In these models the stress variable has the form of the Bishop (1959) stress:…”

Section: Introductionmentioning

confidence: 99%

“…The additional scalar variable is given either by suction or by degree of saturation depending on the specific model, with the exception of the model of Karube & Kawai (2001), in which it is a function of both suction and degree of saturation. Although such models explicitly introduce the degree of saturation in the definition of the soil variables, they still present limitations when predicting important aspects of unsaturated soil behaviour unless the additional complexity of multiple yield surfaces is introduced.…”

Section: Introductionmentioning

confidence: 99%

An elasto-plastic model for unsaturated soil incorporating the effects of suction and degree of saturation on mechanical behaviour

et al. 2003

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Citation for published item:qllipoliD hF nd qensD eF nd hrmD F nd untD tF @PHHQA 9en elstoEplsti model for unsturted soil inorporting the e'ets of sution nd degree of sturtion on mehnil ehviourF9D q¡ eotehniqueFD SQ @IAF ppF IPQEIQTF Further information on publisher's website: httpXGGwwwFthomstelfordFomGjournlsGstrtFspctournlitleaq¡ eotehniqueertileshaIQITtournlwenuatruetourn Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. An elasto-plastic model for unsaturated soil incorporating the effects of suction and degree of saturation on mechanical behaviour D. GA LLIPOLI, Ã A . GENS, Ã R. SH ARMA{ and J. VAUNAT Ã The paper presents an elasto-plastic model for unsaturated soils that takes explicitly into account the mechanisms with which suction affects mechanical behaviour as well as their dependence on degree of saturation. The proposed model is formulated in terms of two constitutive variables directly related to these suction mechanisms: the average skeleton stress, which includes the average fluid pressure acting on the soil pores, and an additional scalar constitutive variable, î, related to the magnitude of the bonding effect exerted by meniscus water at the inter-particle contacts. The formulation of the model in terms of variables closely related to specific behaviour mechanisms leads to a remarkable unification of experimental results of tests carried out with different suctions. The analysis of experimental isotropic compression data strongly suggests that the quotient between the void ratio, e, of an unsaturated soil and the void ratio e s , corresponding to the saturated state at the same average soil skeleton stress, is a unique function of the bonding effect due to water menisci at the inter-particle contacts. The same result is obtained when examining critical states at different suctions. Based on these observations, an elastoplastic constitutive model is developed using a single yield surface the size of which is controlled by volumetric hardening. In spite of this simplicity, it is shown that the model reproduces correctly many important features of unsaturated soil behaviour. It is especially remarkable that, although only one yield surface is used in the formulation of the model, the irreversible behaviour in wetting-drying cycles is well captured. Because of the behaviour normalisation achieved by the model, the resulting constitutive law is economical in terms of the number of tests required for parameter determination.KEYWORDS: clays; constitutive rela...

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The role of pore water in the mechanical behavior of unsaturated soils

Cited by 41 publications

References 10 publications

Effect of Pore-Water Surface Tension on Tensile Strength of Unsaturated Sand

Effect of Pore-Water Surface Tension on Tensile Strength of Unsaturated Sand

Bridging Effective Stress and Soil Water Retention Equations in Deforming Unsaturated Porous Media: A Thermodynamic Approach

An elasto-plastic model for unsaturated soil incorporating the effects of suction and degree of saturation on mechanical behaviour

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