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Dispersivity, collapsibility and microstructure of a natural dispersive loess from Iran

Sadeghi, H ; Sharif University of Technology | 2020

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  1. Type of Document: Article
  2. Publisher: Asian Regional Conference on Soil Mechanics and Geotechnical Engineering , 2020
  3. Abstract:
  4. A new type of collapsible soil was encountered in Southern Iran and caused some serious technical problems including subsidence, collapse and sinkholes during the construction of Zahedan-Chabahar railway. Field observations indicated that in-situ soil contains excessive amount of salts resulting in dispersive features in response to seepage forces in addition to its collapsibility. Therefore, a systematic research plan including field sampling and laboratory testing was carried out to investigate the observed geotechnical features. Results of physio-chemical tests revealed the dominance of Sodium in excess of 70% relative to total dissolved salts, which results in high dispersive potential. In addition, intact soil was observed to show a significant collapse potential of 16% upon wetting because of its low dry density. Compacted soil at the same dry density, on the other hand, showed even higher collapsibility at lower stress levels because the lack of structural bonding provided by calcite in the intact soil. More interestingly, the collapse potential was shown to be dependent on pore water salinity. A reduction in salt concentration in pore water can increase collapse potential to more than 4% because of an increase in the thickness of diffuse double layer. The observed macroscopic behavior was assigned to microstructural features supported by SEM photos. Copyright © Soil Mechanics and Geotechnical Engineering, ARC 2019.All rights reserved
  5. Keywords:
  6. Collapse ; Dispersive loess ; Microstructure ; Natural soils ; Water salinity ; Calcite ; Chemical bonds ; Salts ; Soil mechanics ; Soils ; Water ; Diffuse double layers ; Macroscopic behaviors ; Microstructural features ; Physio-chemical tests ; Pore water salinities ; Salt concentration ; Systematic research ; Total dissolved salts ; Geotechnical engineering
  7. Source: 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019, 14 October 2019 through 18 October 2019 ; 2020
  8. URL: https://www.researchgate.net/publication/338335662_Dispersivity_collapsibility_and_microstructure_of_a_natural_dispersive_loess_from_Iran