Experimental study of strain localization in sensitive clays

Gylland, Anders Samstad; Jostad, Hans Petter; Nordal, Steinar

doi:10.1007/s11440-013-0217-8

Cited by 53 publications

(26 citation statements)

References 27 publications

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“…In contrast, the second phase is referred to as a residual phase, which is attained at larger strains. A number of experimental studies conducted (Gylland 2014;Gylland et al 2014;Thakur et al 2014) show that the post-peak softening behaviour of soft sensitive Norwegian clays in the first phase is significantly influenced by the rate of shearing -more specifically, shear-induced pore pressure and localized drainage in the shear band influence the strength degradation rate and shear band thickness. These observations are consistent with previous studies on soft Swedish clay (Bernander and Svensk 1982;Bernander et al 1985).…”

Section: Modeling Of Post-peak Shear Strength Degradation Of Sensitivmentioning

confidence: 99%

Modeling of large-deformation behaviour of marine sensitive clays and its application to submarine slope stability analysis

et al. 2016

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Post-slide investigations suggest that many large-scale submarine landslides occur through marine sensitive clay layers. A nonlinear mathematical model for post-peak degradation of undrained shear strength of sensitive clay is proposed based on experimental results. A method for estimation of model parameters is presented. Incorporating the model, an analytical solution is developed to examine possible mechanisms of large-scale submarine landslides. Analyses are performed for mild infinite slopes where the failure initiates from a "fully weakened zone" of soil having undrained shear strength lower than the shear stress acting parallel to the slope. The driving force, in excess of resistance, generated from the fully weakened zone is then transferred to the surrounding soil elements resulting in shear band formation due to strain-softening behaviour of sensitive clays. When the length of the fully weakened zone is greater than a critical length, catastrophic shear band propagation (self-driven without any additional external force) occurs, which could result in large-scale offshore landslides. A simple design chart is developed to calculate the critical length. Compared with a 2005 study by Puzrin and Germanovich based on a linear post-peak shear strength degradation model, the present study gives a conservative estimation of critical length for catastrophic shear band propagation.Key words: sensitive clay, large deformation, submarine landslides, shear band, undrained shear strength.Résumé : Les enquêtes post-glissement de terrain suggèrent que de nombreux glissements de terrain sous-marin à grande échelle se produisent à travers les couches d'argiles marines sensibles. Un modèle mathématique non linéaire de la dégradation post-pic de la résistance au cisaillement non drainée de l'argile sensible est proposé sur la base de résultats expérimentaux. Une méthode d'estimation de paramètres du modèle est présentée. Incorporant le modèle, une solution analytique est développée pour examiner les mécanismes possibles de glissements de terrain sous-marin à grande échelle. Les analyses sont effectuées pour des pentes infinies douces où l'échec est entamé à partir d'une « zone totalement affaiblie » du sol ayant une résistance au cisaillement non drainé inférieure à la contrainte de cisaillement agissant parallèlement à la pente. La force d'entraînement, au-delà de la résistance, générée à partir de la zone entièrement affaiblie est transférée aux éléments de sol environnant aboutissant en la formation de bandes de cisaillement en raison du comportement d'adoucissement à la déformation des argiles sensibles. Lorsque la longueur de la zone entièrement affaiblie est supérieure à une longueur critique, une propagation d'une bande de cisaillement catastrophique (auto-conduit sans aucune force externe supplémentaire) se produit qui pourrait entraîner des glissements de terrain en mer à grande échelle. Un graphique de conception simple est développé pour calculer la longueur critique. Par rapport à une étude réalisée e...

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Section: Modeling Of Post-peak Shear Strength Degradation Of Sensitivmentioning

confidence: 99%

Modeling of large-deformation behaviour of marine sensitive clays and its application to submarine slope stability analysis

et al. 2016

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“…Their work is also further developed in the workshop proceedings (L´Heureux et al,2013), in papers by e.g. Locat et al (2008Locat et al ( , 2011Locat et al ( , 2013Locat et al ( , 2015, Gylland et al (2014), Bonadies et al (2014), Zhang et al (2015) and in the editorial by Puzrin (2016). Focus is often on material properties and on numerical solutions of various kinds, e.g.…”

mentioning

confidence: 95%

Downhill progressive landslides in long natural slopes: triggering agents and landslide phases modeled with a finite difference method

et al. 2016

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A large landslide in Tuve (Gothenburg, Sweden 1977) initiated the development of a model for slope stability analysis taking the deformation-softening of soft sensitive clays into consideration. The model studies triggering agents and five phases in progressive slope failure are identified: (1) in-situ, (2) disturbance, (3) unstable 'dynamic', (4) transitory (or permanent) equilibrium, and (5) 'global' failure. The clay resistance in these phases may differ widely; mostly due to different rates of loading.Two time dependent failure criteria are defined: (i) the triggering load condition in the disturbance Phase (2), and (ii) the transitory equilibrium in Phase (4), indicating whether minor downhill displacements or a veritable landslide catastrophe will occur. The analysis explains why downhill landslides tend to spread over vast areas of almost horizontal ground further down-slope. The model has been applied to landslides in Scandinavia and Canada.Three case studies are briefly discussed.The model is a finite difference approach, where local downhill deformations caused by normal forces is maintained compatible with deviatory shear deformations above the potential (or the established) failure surface. Software and an easy-to-use spreadsheet are introduced as well as recent developments. KeywordsLandslides in long natural slopes, Progressive failure in different phases, Triggering agents, Effects of time and rate of loading, Two main failure criteria, Invalidity of one singular static load condition, Massive spread over level ground, Finite difference method of analysis.

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“…By comparing the shear zones for the two rates in Figs 6(a) and 6(b) it is indicated that the zone is thicker for the lower rate. This suggests some impact of local drainage on the shear zone outline along the lines discussed by Gylland et al (2013).…”

Section: Failure Geometrymentioning

confidence: 80%

Micro-level investigation of the in situ shear vane failure geometry in sensitive clay

Gylland¹,

Jostad²,

Nordal³

et al. 2013

Géotechnique

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The circumferential failure surface of a shear vane in strain softening soft sensitive clay is studied. A set of shear vane experiments are performed in situ, where the sheared region is retrieved from the ground using an over-coring technique. By producing thin sections, the circumferential failure zone is revealed when viewed under a polarised light microscope. The failure zone is found to first evolve after reaching the peak global resistance. Its shape is not a full cylinder, but rather a rounded square. The structure of the shear zone is non-smooth and characterised by complex shear patterns of micrometre size.

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Experimental study of strain localization in sensitive clays

Cited by 53 publications

References 27 publications

Modeling of large-deformation behaviour of marine sensitive clays and its application to submarine slope stability analysis

Modeling of large-deformation behaviour of marine sensitive clays and its application to submarine slope stability analysis

Downhill progressive landslides in long natural slopes: triggering agents and landslide phases modeled with a finite difference method

Micro-level investigation of the in situ shear vane failure geometry in sensitive clay

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