Abstract
The formation of the shear band is associated with the failure of soil. However, there has been relatively little investigation on the evolution of shear bands in naturally structured clay with a high sensitivity. In this study, undrained plane strain compression tests, digital image correlation (DIC) analyses, and scanning electron microscopy (SEM) tests were performed to investigate the characteristics of shear bands in naturally structured clay. The basic mechanical properties and stress–strain relationships show that naturally structured clay exhibits a strong structure and high sensitivity. Compared with plane strain compression tests under low confining pressure, more localized shear bands emerge in the specimens during the tests under high confining pressures; however, when the specimens fail, only one shear band is fully developed, and the local deformation in the developed shear band is much larger than those in other localized shear bands. Moreover, the local stress–strain relationships inside and outside the shear band show distinct discrepancies. The SEM results show distinct micro-structures of clays inside and outside the shear band, which are caused by the development of the shear band. The findings in this work provide new insight into the failure of structured clay.
Highlights
Shear band is defined as a band-shaped zone where the strain inside the zone is significantly greater than that outside the zone when the soil is subjected to external forces
As the axial strain increases, the deviatoric stress first increases to a peak and decreases, and the peak deviatoric stress appears at a small axial strain, exhibiting the typical stress–strain behavior of naturally structured clay
Significant differences in stress–strain behavior are observed between the other natural clays and Zhanjiang clay; the stress–strain curves of the former either do not indicate a remarkable peak deviatoric stress, or the peak deviatoric stress appears at εz ≥ 5% [18,19,26]
Summary
Shear band is defined as a band-shaped zone where the strain inside the zone is significantly greater than that outside the zone when the soil is subjected to external forces. The formation of a shear band significantly affects the failure of soil [1,2,3,4]; when the external load of the soil is higher than the strength of the soil, shear failure will occur along the shear band. Structured clay possesses complicated mechanical properties owing to soil structure. Researchers conducted extensive research on its mechanical behavior, including its compressibility and shear strength [7,8,9]. The mechanical properties of specimens under consolidation stress lower and higher than yield stress differ significantly. In oedometer tests, when the effective vertical stress is lower than the yield stress, undisturbed specimens show low compressibility; when the effective vertical stress is higher than the yield stress, undisturbed specimens show high compressibility
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