Evolution of microstructure in compacted London Clay during wetting and loading

Monroy, Rafael; Zdravković, Lidija; Ridley, Andrew

doi:10.1680/geot.8.p.125

Cited by 205 publications

(105 citation statements)

References 25 publications

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“…8). In addition, microstructural studies have reported that the soil fabric during drying is also evolving into a more constricted porosity centred at the microporosity range, although it recovers some of the macroporosity when it is subsequently wetted (Cuisinier & Laloui, 2004;Monroy et al, 2010). These results are also consistent with the small strain shear modulus studies on decomposed tuff and Bonny silt conducted by Ng & Xu (2012) and Khosravi & McCartney (2012).…”

Section: Resultssupporting

confidence: 74%

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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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Section: Resultssupporting

confidence: 74%

“…As illustrated in past literature through computed tomography and mercury intrusion techniques, the soil structure would also change from a predominantly aggregated assembly on the dry side of OMC to a more matrix-dominated macrostructure on the wet side of OMC (e.g. Delage et al, 1996;Monroy et al, 2010).…”

Section: Resultsmentioning

confidence: 97%

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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“…It was soon accepted that water was trapped inside the clay aggregations, even if the mixture remained relatively dry. These ideas have been widely confirmed by subsequent studies (Delage et al, 1996;Romero & Simms, 2008;Lee & Zhang, 2009;Monroy et al, 2010).…”

Section: Introductionsupporting

confidence: 52%

“…However, this is not always the case. Wetting tests reported by Monroy et al (2010) on statically compacted high-plasticity London Clay indicate that changes in micropores may also be significant on wetting. The higher activity of the clay probably explains the enhanced sensitivity of microporosity to suction changes.…”

Section: Microstructure and Compacted Soil Behaviourmentioning

confidence: 96%

Compacted soil behaviour: initial state, structure and constitutive modelling

Alonso¹,

Pinyol²,

Gens³

2013

Géotechnique

184

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The paper explores the behaviour of compacted soils throughout the (dry density-water content) compaction plane by means of a conceptual framework that incorporates microstructural information. The engineering properties of compacted soils are described by an initial state in terms of a yielding stress, soil suction and a microstructural state variable. Microstructure is defined by the ratio of microvoid volume to total void volume. The pattern of variation of the microstructural parameter within the compaction plane has been determined, for some compacted soils, by analysing mercury intrusion porosimetry data. The microstructure of wet and dry compaction conditions can then be quantified. To ensure consistency, the framework is cast in the form of a constitutive model defined in terms of an effective suction and a constitutive stress that incorporate the microstructural variable. The model is shown to be consistent with a number of experimental observations and, in particular, it explains the intrinsic collapse potential of compacted soils. It predicts, for a common initial suction, a higher collapse potential for dry of optimum conditions than for wet compaction. It also predicts in a natural manner the observed evolution of soil compressibility during drained or undrained loading. Model capabilities are illustrated by application to a testing programme on statically compacted samples of low-plasticity silty clay. The compression behaviour of samples compacted wet and dry of optimum and the variation of collapse strains with confining stress have been successfully reproduced by the model.

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“…Detailed descriptions of the mechanical and water retention aspects related to the evolving nature of the microstructure of compacted double-porosity clayey soils can be found elsewhere (e.g. [4,6,19,46,52]). Finally, anisotropy of soil behaviour is not considered in the paper, with the aim of focusing on saturation and de-saturation processes in soils without important direction-dependent response.…”

Section: Introductionmentioning

confidence: 99%

From saturated to unsaturated conditions and vice versa

et al. 2017

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Representing transitions between saturated and unsaturated conditions, during drying, wetting and loading paths, is a necessary step for a consistent unification between saturated and unsaturated soil mechanics. Transitions from saturated to unsaturated conditions during drying will occur at a nonzero air-entry value of suction, whereas transitions from unsaturated to saturated conditions during wetting or loading will occur at a lower nonzero air-exclusion value of suction. Air-entry and airexclusion values of suction for a given soil will differ (representing hysteresis in the retention behaviour) and both are affected by changes in the dry density of the soil or by the occurrence of plastic volumetric strains. The paper demonstrates, through model simulations and comparison with experimental data from the literature (covering drying, wetting and loading tests), that the Glasgow Coupled Model (GCM), a coupled elasto-plastic constitutive model covering both mechanical and retention behaviour, represents transitions between unsaturated and saturated behaviour in a consistent fashion. Key aspects of the GCM are the use of Bishop's stress tensor for mechanical behaviour, the additional influence of degree of saturation on mechanical yielding, inclusion of hysteresis in the retention behaviour, and the role of plastic volumetric strains (and not total volumetric strains) in the description of the water retention response. The success of the GCM in representing consistently transitions between saturated and unsaturated conditions, together with subsequent mechanical and retention responses, demonstrates the potential of this coupled constitutive model for numerical modelling of boundary value problems involving saturated and unsaturated conditions.

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Evolution of microstructure in compacted London Clay during wetting and loading

Cited by 205 publications

References 25 publications

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

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

Compacted soil behaviour: initial state, structure and constitutive modelling

From saturated to unsaturated conditions and vice versa

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