Tensile Strength Characteristics of Unsaturated Sands

Lu, Ning; Wu, Bailin; Tan, C.P.

doi:10.1061/(asce)1090-0241(2007)133:2(144)

Cited by 181 publications

(100 citation statements)

References 19 publications

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“…Tensile strength is related to a number of different forces and bonds (Wiebe et al 1998;Lu et al 2007;Tang et al 2015) some of which depend more strongly on temperature and water content than others. In general, four different forces and bonds can be distinguished: (1) van der Waals force, (2) electrical double-layer forces between clay mineral surfaces, (3) capillary forces at water bridges, and (4) bonds between grains caused by mineral precipitates from evaporating water.…”

Section: Tensile Strengthmentioning

confidence: 99%

“…At first, more water bridges are formed and the number of capillary contacts between water and solid surfaces increases. With a further increase of the water content, however, the pore space becomes more saturated and the water bridges merge (Lu et al 2007;Tang et al 2015;Song et al 2012). The surfaces of more and more grains become completely wetted, and the cohesion between the particles decreases.…”

Section: Tensile Strengthmentioning

confidence: 99%

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Neutron Radiographic Study of the Effect of Heat-Driven Water Transport on the Tensile Strength of Bentonite-Bonded Moulding Sand

et al. 2017

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Wet tensile testing is a common method to assess the stability of bentonite-bonded moulding sands. For wet tensile testing, a specimen is first heated from above in order to simulate heat-driven moisture transport induced by the casting process. Then, tensile stress is applied until rupture. In this study, neutron radiography imaging was applied to moulding sands in situ during heating and wet tensile testing in order to investigate the effects of water kinematics on the tensile strength. Neutron radiography allowed the localization of the rupture plane and the quantitative determination of the local water content with sub-mm resolution. Quantification of the temperature at the rupture plane and of the heat kinematics within the specimen was accomplished by temperature measurements both in situ and ex situ. In this way, experimental data correlating the wet tensile strength with the specific conditions of moulding sands at the rupture plane were obtained for the first time. that the weakest location within a sand profile can be pinpointed at the interface between evaporation and condensation zone (i.e. at the 100 • C isotherm), where water vaporization starts and the water bridges connecting the sand grains collapse. This weakest location has maximum strength, if the local water content at the rupture plane is between 5 and 9 wt.%. Less water leads to a strong decrease of wet tensile strength. More water requires an initial water content above 5 wt.%, which leads to a decrease of the tensile strength of the unheated sand.

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Section: Tensile Strengthmentioning

confidence: 99%

Section: Tensile Strengthmentioning

confidence: 99%

Neutron Radiographic Study of the Effect of Heat-Driven Water Transport on the Tensile Strength of Bentonite-Bonded Moulding Sand

et al. 2017

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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%

“…This causes an increase in effective stress. Many researchers have attempted to describe the behaviour of soil in the range between the two extremes by extending Terzaghi's classic effective stress equation (Bishop and Blight 1963;Lambe and Whitman 1969;Mitchell 1976;Fredlund and Morgenstern 1977;Kohgo et al 1993aKohgo et al , 1993bKhalili et al 2004;Likos 2004, 2006;Lu et al 2009). …”

Section: (2-21)mentioning

confidence: 99%

“…This point, shown in Figure 2.12 on the far left of negative normal stress axis, represents isotropic tensile strength ( ). Isotropic tensile strength is defined as the interparticle bonding stress developed in unsaturated granular soil by surface tension and negative pore water pressure (Lu et al 2009 (Sture et al 1998;Khalili and Khabbaz 1998;Kim 2001;Khalili et al 2004). Compared to nine-parameter micro-mechanical framework, macro-mechanical model uses only four parameters, but the effectiveness and reliability of one model over the other is yet to be verified.…”

mentioning

confidence: 99%

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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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Estimating water retention curves and strength properties of unsaturated sandy soils from basic soil gradation parameters

Wang

Baudin

et al. 2017

Water Resources Research

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This study proposed two pedotransfer functions (PTFs) to estimate sandy soil water retention curves. It is based on the van Genuchten's water retention model and from a semiphysical and semistatistical approach. Basic gradation parameters of d60 as particle size at 60% passing and the coefficient of uniformity Cu are employed in the PTFs with two idealized conditions, the monosized scenario and the extremely polydisperse condition, satisfied. Water retention tests are carried out on eight granular materials with narrow particle size distributions as supplementary data of the UNSODA database. The air entry value is expressed as inversely proportional to d60 and the parameter n, which is related to slope of water retention curve, is a function of Cu. The proposed PTFs, although have fewer parameters, have better fitness than previous PTFs for sandy soils. Furthermore, by incorporating with the suction stress definition, the proposed pedotransfer functions are imbedded in shear strength equations which provide a way to estimate capillary induced tensile strength or cohesion at a certain suction or degree of saturation from basic soil gradation parameters. The estimation shows quantitative agreement with experimental data in literature, and it also explains that the capillary‐induced cohesion is generally higher for materials with finer mean particle size or higher polydispersity.

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Tensile Strength Characteristics of Unsaturated Sands

Cited by 181 publications

References 19 publications

Neutron Radiographic Study of the Effect of Heat-Driven Water Transport on the Tensile Strength of Bentonite-Bonded Moulding Sand

Neutron Radiographic Study of the Effect of Heat-Driven Water Transport on the Tensile Strength of Bentonite-Bonded Moulding Sand

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

Estimating water retention curves and strength properties of unsaturated sandy soils from basic soil gradation parameters

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