Critical-state parameters for an unsaturated residual sandy clay

Citation for published item:tquinD F eF nd eugrdeD gF iF nd qllipoliD hF nd ollD hF qF @PHHWA 9he strength of unstilised rmmed erth mterilsF9D q¡ eotehniqueFD SW @SAF ppF RVUERWHF Further information on publisher's website: httpXGGdxFdoiForgGIHFITVHGgeotFPHHUFHHIPW 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. Rammed earth is a manufactured material comprising sand, gravel and clay, which is compacted between forms to build walls. Primarily a historic method of construction, it is now receiving considerable interest worldwide owing to its zero reliance on materials such as cement, and its potential for recycling. Despite its longevity, the source of its shear strength is poorly understood. This paper presents initial laboratory test results that point to the main source of strength in rammed earth being suction, and indicating that recent advances in unsaturated soil mechanics may also be applied to this material.

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“…The plot shows the rate of suction change reducing with axial strain, as seen in other studies of unsaturated soils (e.g. Toll & Ong, 2003).…”

Section: Results and Interpretationsupporting

confidence: 59%

“…Toll & Ong (2003) show that the contribution to strength from suction in a sandy clay reduces as the degree of saturation reduces. So, although suction increases as the soil dries out, the contribution to strength reaches a peak and then drops away (Toll, 1991).…”

Section: A Geotechnical Materialsmentioning

confidence: 90%

The strength of unstabilised rammed earth materials

et al. 2009

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“…The values in Table 2 are plotted against degree of saturation in Residual Zone from net stress than a saturated material. This is consistent with the argument made by Toll (1990) and Toll and Ong (2003) that the aggregated fabric of a clayey soil could be supported by suction, effectively responding as if it were a "coarser" material, as finer particles are held together to behave as larger particles. It is interesting to see that this can also occur in a cemented sandy soil.…”

Section: Suction Component M Bsupporting

confidence: 90%

“…Toll (1990) and Toll & Ong (2003) expressed the unsaturated critical state concept (represented by equation [4]) in the more general stress invariants:…”

Section: Framework For Unsaturated Soilsmentioning

confidence: 99%

Critical state shear strength of an unsaturated artificially cemented sand

Toll

Rahman

2017

Géotechnique

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This paper presents the results of a set of 22 triaxial tests on an unsaturated artificially cemented sand. The results are used to explore the applicability of a number of unsaturated soil frameworks for interpreting the shear strength. Constant water content triaxial tests were carried out on unsaturated specimens, using the axis translation technique to measure suctions during shearing. The test results on the unsaturated material were referenced against a series of drained and undrained triaxial tests that were carried out on saturated specimens. The results of the unsaturated tests were analysed to investigate the effect of the suction and degree of saturation on the shear strength at the critical state. The results show that the critical state stress ratio in terms of net stress (Ma) was found to be larger than the saturated critical state stress ratio (Ms). It was also found that the stress ratio in terms of suction (Mb) reduced as suction increased (when the degree of saturation reduced below 30%). Interestingly, during the initial desaturation phase when the degree of saturation reduces considerably, the stress ratio Mb was largely unaffected by desaturation. It was only when the suction increased sufficiently that the micro-voids within the cementing material could start to desaturate that a reduction in Mb was seen. This occurred at suctions in excess of the residual suction when the global degree of saturation was changing very little. This implies that the suction is contributing to the strength of the cementing material itself.

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“…Furthermore, this change of soil microstructure caused by variations in the compaction induced states (i.e. water content and compaction effort), often results in distinct mechanical and hydraulic behaviour (Toll & Ong, 2003;Bagherieh et al, 2009;Sheng & Zhou, 2011).…”

Section: Introductionmentioning

confidence: 99%

The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying–wetting cycles

2015

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Heitor, A., Indraratna, B. & Rujikiatkamjorn, C. (2015). The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying -wetting cycles. Geotechnique: international journal of soil mechanics, 65 (9), 717-727.The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying -wetting cycles AbstractThe elastic properties of a soil are usually investigated to describe its engineering behaviour. The results of previous studies indicate that the effect of changes in suction on the elastic response at a small strain level of soils is significant during compaction and post-compaction periods. Limited efforts have been focused on quantifying those post-compacted responses due to the changes in suction induced by wetting and drying cycles. During their service life, most earth structures experience changes in hydraulic behaviour owing to climatic changes. These seasonal fluctuations in turn impact on the geomechanical performance of compacted soil. In this paper the aspects related to the elastic properties of compacted soils subjected to cycles of drying and wetting are described. Particular emphasis is placed on the effect of compaction energy on the hysteric behaviour (i.e. amplitude of the hysteresis loop) and its dependence on the initial stress state conditions and suction history. The results not only confirm the importance of the current suction in governing the shear and compression velocities and associated moduli, but they also suggest that subsequent drying-wetting cycles or suction history can further induce hysteretic changes, particularly along the wetting paths. The elastic properties of a soil are usually investigated to describe its engineering behaviour. The results of previous studies indicate that the effect of changes in suction on the elastic response at a small strain level of soils is significant during compaction and post-compaction periods. Limited efforts have been focused on quantifying those post-compacted responses due to the changes in suction induced by wetting and drying cycles. During their service life, most earth structures experience changes in hydraulic behaviour owing to climatic changes. These seasonal fluctuations in turn impact on the geomechanical performance of compacted soil. In this paper the aspects related to the elastic properties of compacted soils subjected to cycles of drying and wetting are described. Particular emphasis is placed on the effect of compaction energy on the hysteric behaviour (i.e. amplitude of the hysteresis loop) and its dependence on the initial stress state conditions and suction history. The results not only confirm the importance of the current suction in governing the shear and compression velocities and associated moduli, but they also suggest that subsequent drying-wetting cycles or suction history can further induce hysteretic changes, particularly along the wetting paths.

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Critical-state parameters for an unsaturated residual sandy clay

Cited by 28 publications

References 16 publications

The strength of unstabilised rammed earth materials

The strength of unstabilised rammed earth materials

Critical state shear strength of an unsaturated artificially cemented sand

The role of compaction energy on the small strain properties of a compacted silty sand subjected to drying–wetting cycles

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