Microstructural observations of shear zones in sensitive clay

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

doi:10.1016/j.enggeo.2013.06.001

Cited by 22 publications

(8 citation statements)

References 29 publications

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“…After sample cutting, the frozen blocks were carefully oven dried based on author's previous experience on drying 8 techniques. Subsequent resin impregnation was carried out both on carefully carved smaller pieces and directly in the areas around the cone and the shaft (Gylland et al 2013). A low viscosity epoxy resin was used to avoid disturbance of the soil microstructure.…”

Section: Thin Sectionsmentioning

confidence: 99%

Microstructural study of deformation zones during cone penetration in silt at variable penetration rates

et al. 2015

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This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link AbstractDuring conventional cone penetration testing in silt, the soil will normally be partially drained.If the penetration rate varies, time for drainage is altered and therefore the measured cone resistance and pore pressure will change. This paper studies the change in soil microstructure around the probe during cone penetration carried out at different penetration rates to investigate the failure mechanism and the processes controlling drainage in silt. Backscattered electron images of polished thin sections prepared from frozen samples at the end of penetration were used. Making use of advanced image processing techniques, the statistical distribution of particle orientations and the local porosity were investigated for the zones around the cone tip and the shaft. The spatial distribution of the measured microscale parameters in the region near the probe indicates that the soil deformation during CPTU in silt leads to the formation of both contractive and dilative zones. The macro response of the material, presented by the pore pressure and the cone penetration resistance measured during the test, results from the competition between these zones during penetration, which is shown to be dependent on the penetration rate.

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Section: Thin Sectionsmentioning

confidence: 99%

Microstructural study of deformation zones during cone penetration in silt at variable penetration rates

et al. 2015

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“…At a very large strain, remoulding of soil together with reorientation of particles reduce s u to the residual shear strength (s ur ), as observed from a close examination of soil after vane shear tests (Gylland et al 2013). Bernander (2000) suggested that s ur does not generally mobilize in a developing slip surface and therefore recommended an undrained shear strength s uR (>s ur ) for modelling progressive failure of sensitive clay slopes.…”

Section: Post-peak Shear Strength Degradationmentioning

confidence: 99%

Large-deformation finite-element modelling of earthquake-induced landslides considering strain-softening behaviour of sensitive clay

et al. 2019

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Large-scale landslides in sensitive clays cannot be explained properly using the traditional limit equilibrium or Lagrangian-based finite-element (FE) methods. In the present study, dynamic FE analysis of sensitive clay slope failures triggered by an earthquake is performed using a large-deformation FE modelling technique. A model for post-peak degradation of undrained shear strength as a function of accumulated plastic shear strain (strain-softening) is implemented in FE analysis. The progressive development of “shear bands” (the zone of high plastic shear strains) that causes the failure of a number of soil blocks is simulated successfully. Failure of a slope could occur during an earthquake and also at the post-quake stage until the failed soil masses come to a new static equilibrium. Upslope retrogression and downslope runout of the failed soil blocks are examined for varying geometries and soil properties. The present FE simulations can explain some of the conditions required for different types of seismic slope failure (e.g., spread, flowslide or monolithic slides) to be triggered, as observed in the field.

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“…e microscopic structure of soil has direct influence on the strength, consolidation characteristics, and permeability properties, which are of great significance to the study of microscopic structure of soil. Gylland et al [1] studied the effect of microstructural changes of clay on shear strength. Zhang et al [2] applied a digital imaging method to investigate the evolution of microscopic pore of soft clay in the process of consolidation, and it was found that the consolidation process has an effect of adjusting on the gradation of microscopic pores.…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation and Microscopic Stress Mechanism for the Microscopic Pore Deformation during Soil Compression

Tao

Peng

Xiao

et al. 2019

Advances in Civil Engineering

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Pore structure is closely related with strength, constitutive relation, consolidation characteristics, and permeability properties of soil. Consequently, improving the understanding of the relationship between microscopic structure and macroscopic physical and mechanical properties has extremely important scientific significance. A large number of studies have shown that pores of soil have fractal features, and hence, the carpet model can be used to approximately simulate the fractal structure of clay. In the present study, ANSYS software was selected to establish a microscopic model of clay to study the distribution of microscopic stress and microscopic deformation characteristics of pores under different consolidation pressures. Besides, the variation law of microscopic pore size was quantitatively determined by using IPP (Image-Pro Plus) software. Combined with the fractal theory, the changes of microscopic pore of numerical simulation and that of physical experiment during compression of clay are studied. All the results indicated that the microscopic stress distribution of clay is not uniform on the compaction process. The larger the pore size is, the bigger the compression stress on both sides and the greater the bending deformation of upper part of the pore is, which leads to the deformation of larger pores which is bigger than that of smaller pores. Based on the results, issues about the microscopic mechanism of the difference in vertical and horizontal permeability under compression of clay, the relationship between the changes of pore shape and microscopic stress, the preliminary principle of “preferential crush of larger particles” for granular soil, skeleton stress across the region where stiffness is relative larger, and the self-protection of particles and pores are also discussed. The results of this study are of great importance in understanding of soil compression and related physical and mechanical properties from the microscopic view.

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Microstructural observations of shear zones in sensitive clay

Cited by 22 publications

References 29 publications

Microstructural study of deformation zones during cone penetration in silt at variable penetration rates

Microstructural study of deformation zones during cone penetration in silt at variable penetration rates

Large-deformation finite-element modelling of earthquake-induced landslides considering strain-softening behaviour of sensitive clay

Numerical Simulation and Microscopic Stress Mechanism for the Microscopic Pore Deformation during Soil Compression

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