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The onset of static liquefaction in anisotropically consolidated soils is of relevance in assessing the performance of geotechnical systems. Previous studies have also highlighted the role of inherent soil fabric. This study derives an analytical instability criterion for granular materials under undrained loading by using the relatively new anisotropic critical state theory (ACST). The criterion is established using the SANISAND-F model, and it is amenable to incorporating consolidation anisotropy and fabric effects. We assess different numerical strategies for simulating the instability onset on materials sheared from initially anisotropic conditions. Our assessments indicate that simulations that consider consolidation followed by shear better represent the response observed in laboratory tests. It is observed that the degree of anisotropic consolidation has no significant effect on the instability stress ratio, but a very high degree of anisotropic consolidation results in a spontaneous collapse. It is also observed that the anisotropic consolidated specimens have a higher instability stress ratio in triaxial compression than in triaxial extension, highlighting the effect of loading direction relative to the existing fabric.
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Fabric anisotropy effects on static liquefaction under constant shear drained loading
Several case history failures of slope systems have highlighted that the instability onset in loose materials can be triggered under prevailed drained conditions and stress paths that can be represented by constant shear drained (CSD) loading. This study uses the anisotropic critical state theory (ACST) to assess the effect of fabric anisotropy and loading characteristics (e.g., Lode angle and principal stress direction) on the instability onset under CSD stress paths, comparing our numerical-based observations with available experimental information. Towards this end, the ACST-based SANISAND-F model’s performance under CSD stress paths is also assessed. In addition, multiaxial conditions are incorporated through the estimation of instability surfaces. The numerical simulations are useful in explaining that the instability onset under CSD loading is dictated by a trade-off of volumetric strain components. Moreover, the results show an important effect of fabric anisotropy on the instability stress ratio (𝜂𝑓 ). For conditions representative of common experimental setups, 𝜂𝑓 decreases with the increase of the Lode angle and the major principal stress inclination, and 𝜂𝑓 increases with the increase of initial fabric intensity, consistent with available experimental evidence. However, these trends can change based on the interaction between the Lode angle and loading/fabric directions; hence, departing from typical experimental observations. Finally, we discuss the potential of a simplified approach to estimate 𝜂𝑓 analytically, including fabric effects.
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- Award ID(s):
- 2013947
- PAR ID:
- 10511051
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Computers and Geotechnics
- Volume:
- 163
- Issue:
- C
- ISSN:
- 0266-352X
- Page Range / eLocation ID:
- 105724
- Subject(s) / Keyword(s):
- Static liquefactionAnisotropic critical state theoryInstability onsetConstant Shear Drained (CSD)Fabric anisotropy
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.compgeo.2023.105724
