Experimental and numerical studies of the hydromechanical behaviour of a natural unsaturated swelling soil

Nowamooz, Hossein; Mrad, M.; Abdallah, Adel; Masrouri, Farimah

doi:10.1201/9780203884430.ch117

Cited by 9 publications

(10 citation statements)

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“…Several studies have been performed to investigate the effect of wetting and drying on soil physical properties (Alonso et al, 2005;Nowamooz et al, 2009;Rao et al, 2001;Tang et al, 2011). However, the relationship between W-D cycles and desiccation cracking behaviour is still not clearly understood.…”

Section: Introductionmentioning

confidence: 99%

Desiccation and cracking behaviour of clay layer from slurry state under wetting–drying cycles

Tang¹,

Cui²,

Shi³

et al. 2011

Geoderma

288

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a b s t r a c tLaboratory tests were conducted to investigate the effect of wetting-drying (W-D) cycles on the initiation and evolution of cracks in clay layer. Four identical slurry specimens were prepared and subjected to five subsequent W-D cycles. The water evaporation, surface cracks evolution and structure evolution during the W-D cycles were monitored. The effect of W-D cycles on the geometric characteristics of crack patterns was analyzed by image processing. The results show that the desiccation and cracking behaviour was significantly affected by the applied W-D cycles: the measured cracking water content θ c , surface crack ratio R sc and final thickness h f of the specimen increased significantly in the first three W-D cycles and then tended to reach equilibrium; the formed crack patterns after the second W-D cycle were more irregular than that after the first W-D cycle; the increase of surface cracks was accompanied by the decrease of pore volume shrinkage during drying. In addition, it was found that the applied W-D cycles resulted in significant rearrangement of specimen structure: the initially homogeneous and non-aggregated structure was converted to a clear aggregated-structure with obvious inter-aggregate pores after the second W-D cycle; the specimen volume generally increased with increasing cycles due to the aggregation and increased porosity. The image analysis results show that the geometric characteristics of crack pattern were significantly influenced by the W-D cycles, but this influence was reduced after the third cycle. This is consistent with the observations over the experiment, and indicates that the image processing can be used for quantitatively analyzing the W-D cycle dependence of clay desiccation cracking behaviour.

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Section: Introductionmentioning

confidence: 99%

Desiccation and cracking behaviour of clay layer from slurry state under wetting–drying cycles

Tang¹,

Cui²,

Shi³

et al. 2011

Geoderma

288

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“…Figure 1 shows two typical relationships between volumetric strain and suction cycle number separately published by Alonso et al (2005) and Nowamooz et al (2009), where the compressive strains are considered positive. In both tests, the surcharge pressure remained constant and is less than the preconsolidation pressure of the specimen at saturated state to ensure the volumetric strain was induced only by the effect of wetting and drying.…”

Section: Two Swelling-shrinkage Strain Componentsmentioning

confidence: 99%

“…Cyclic wetting and drying test results of expansive clays reported by Alonso et al (2005), Nowamooz et al (2009), andSubba Rao (2009) are adopted for the verification of the presented model. To illustrate capabilities of the presented model, both the predictions of the BExM and the presented model are given for comparison.…”

Section: Performance Of Presented Modelmentioning

confidence: 99%

“…These tests can be grouped into two categories: alternately soaked and dried tests (Dif and Bluemel 1991;Day 1994;Basma et al 1996;Fleureau et al 2002;Tripathy et al 2002;Tripathy and Subba Rao 2009;Lin and Cerato 2013), and cyclic suction-controlled tests (Alonso et al 2005;Nowamooz and Masrouri 2008;Nowamooz et al 2009;Airò Farulla et al 2010). In alternately soaked and dried tests, only water contents of soil specimens are measured directly, therefore the wetting-drying path is usually quantified in terms of volumetric strain versus water content; while in cyclic suction-controlled tests, soil specimens are allowed to swell or shrink in equilibrium with a predetermined applied suction, therefore the wetting-drying path is usually characterized by the relationship between volumetric strain and suction.…”

Section: Introductionmentioning

confidence: 99%

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Modeling swelling–shrinkage behavior of compacted expansive soils during wetting–drying cycles

Wang¹,

Wei

2015

Can. Geotech. J.

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This paper presents a straightforward approach for modelling volume change behavior of expansive soils during wetting-drying cycles. The swelling-shrinkage strain of expansive soils induced by cyclic wetting and drying was decomposed with distinctive physical background into a reversible component, which shows a synchronous change with the cyclic change of suction, and an irreversible component, which is generated mainly in the early stage of the wetting-drying process. The mechanisms of the two swelling-shrinkage strain components can be well explained through the double-level structure of expansive soils and its evolution with mechanical and hydraulic loading. The reversible component originates from the reversible deformation behavior of aggregates, and primarily depends on current suction or water content. The irreversible component is associated with the irreversible change of macrostructure, reflecting the difference in soil structures at current state and the equilibrium state. A practical constitutive model was proposed for compacted expansive clays from a global and phenomenological perspective. The model parameters can be calibrated with observed macroscopic deformation behavior without measuring microstructural parameters. The performance of the presented model was validated by simulating cyclic suctioncontrolled tests as well as an alternately soaked and dried test with irregular amplitudes of suctions.Key words: expansive soils, volumetric behavior, swelling, shrinkage, model. Résumé :Cet article présente une approche directe pour modéliser les variations de volume de sols expansifs durant des cycles de mouillage-séchage. La déformation causée par le gonflement-retrait des sols expansifs induite par les cycles de mouillageséchage a été décomposée, selon des notions physiques, en une composante réversible qui démontre une variation synchrone avec les variations cycliques de succion, et une composante irréversible qui est générée principalement dans les premières étapes du processus de mouillage-séchage. Les mécanismes des deux composantes de la déformation en gonflement-retrait peuvent être bien expliqués grâce à la structure à deux niveaux des sols expansifs et par l'évolution de cette structure avec les charges mécaniques et hydrauliques. La composante réversible provient de la déformation réversible des agrégats, et dépend principalement de la succion présente et de la teneur en eau. La composante irréversible est associée avec les variations irréversibles de la macrostructure, reflétant les différences dans les structures du sol à l'état présent et à l'état d'équilibre. Un modèle constitutif pratique est proposé pour les argiles expansives compactées basé sur une perspective globale et phénomé-nologique. Les paramètres du modèle peuvent être calibrés avec les déformations macroscopiques observées sans mesurer les paramètres microstructuraux. La performance du modèle présenté a été validée en simulant des essais de succion cyclique contrôlés de même d'avec un essai alternant le mouillage...

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“…The osmotic suction technique was imposed on the top and bottom of test specimen by connecting the semi-permeable membrane to the top cap and the base of the device membrane behind which an aqueous solution of large sized polyethylene glycol (PEG) molecules is circulated. Several researchers have used osmotic suction control testing for the evaluation of swelling characteristics of expansive soils [7,2,9,10]. The authors are currently undergoing research to investigate the effect of suction on the swelling behavior, of a locally available expansive soil, in vertical and lateral directions.…”

Section: Introductionmentioning

confidence: 99%

Calibrations for volume change measurements using osmotic suction control technique

2017

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Evaluation of the volume change behavior of expansive soils under controlled suction and boundary conditions is important for the proper design of different geotechnical systems. Osmotic technique was used by several researchers for suction controlled testing of expansive soil specimens. This technique involves circulating polyethylene glycol solution (PEG) over a semipermeable membrane underlying a test specimen. Different suction controlled testing apparatuses incorporating osmotic techniques were developed included triaxial and oedometric testing conditions to simulate different boundary conditions. This paper describes a series of calibration performed on suction controlled modified oedometer and triaxial equipment used for testing expansive soil. The modified oedometer, developed by the authors, comprises of thin-wall oedometer ring instrumented with strain gauges to measure the lateral stresses evolving during the test. The first part of this paper introduces the errors that arise during osmotic suction testing, concerning the device flexibility and PEG solution losses. The second part of the paper highlights the calibration procedure for estimating lateral stresses in modified oedometer from instrumented strain gauges as well as introduces a correction for the temperature fluctuation. Finally, the effect of triaxial cell flexibility on the volume change measured during osmotic suction controlled testing as well as temperature effect on volume change measurements were evaluated and correction procedures were introduced.

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Experimental and numerical studies of the hydromechanical behaviour of a natural unsaturated swelling soil

Cited by 9 publications

References 1 publication

Desiccation and cracking behaviour of clay layer from slurry state under wetting–drying cycles

Desiccation and cracking behaviour of clay layer from slurry state under wetting–drying cycles

Modeling swelling–shrinkage behavior of compacted expansive soils during wetting–drying cycles

Calibrations for volume change measurements using osmotic suction control technique

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