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Development of a High-precision Unsaturated Permeameter for Characterizing Two-phase Flow Through Deformable Porous Media

Hassani Motlagh, Amin | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54637 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Sadeghi, Hamed
  7. Abstract:
  8. Given that highly deformable natural deposits such as collapsible and swelling soils make up more than one-fifth of the land surface and are generally in unsaturated conditions, behavioral measurement of this type of soil including accurate measurement of its hydraulic properties is important. The challenges of designing and implementing construction infrastructure, along with the most reported financial losses due to the presence of these soils, double the importance of studying the behavior of these soils. The large volume changes of these soils in contact with water (equivalent to a volumetric strain of more than 5%) has been a major challenge for researchers in predicting the hydromechanical behavior of these soils. However, so far no systematic and standard laboratory method has been reported to directly measure the hydraulic conductivity function and the gas permeability function in these soils under unsaturated conditions equivalent to two-phase currents that occur mainly in nature. An important example of this limitation, which shows the importance of the present study, is the inability of the methods presented in ASTM D 7664 to measure the hydraulic conductivity function of unsaturated soils with high deformations. Therefore, the main purpose of this study is to design and develop a device to directly measure the permeability function of water and gas in unsaturated soils with high deformation. Also, in the development of the device, in addition to considering the conditions for applying hydraulic gradients and gas pressure, the possibility of applying osmotic gradients during the test sample has been considered. In other words, the new device can be used to study the passage of contaminants through soil insulation layers and also to measure the membrane efficiency factor of these layers in environmental geotechnics studies, including the design of municipal landfill cover in saturated and unsaturated conditions. It should be noted that the validity of the latter case is beyond the scope of this study. Due to the inclusion of dual cells in the design of this device, the amount of change in the volume of highly deformable soil samples during the wetting process, complete saturation, and drying and wetting cycles can be obtained in all possible experiments. Therefore, this device has higher accuracy in terms of considering and monitoring sample volume changes during hydromechanical loading-loading processes by reducing the maximum errors of hydraulic conductivity measurement errors compared to other triaxial permeability devices presented in technical texts so far. In general, the purpose of this study is to develop a double-cell triaxial device to measure the permeability function of water and gas in unsaturated soils with high deformation and also to investigate the effect of fluid with different osmotic potential and gradient on this function
  9. Keywords:
  10. Hydraulic Conductivity ; Unsaturated Soil ; Matric Suction ; Osmotic Suction ; Triaxial Permeameter Device ; Highly Deformable Soils ; Collapsible Soils

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