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Development of Unsaturated Triaxial Device in Order to Conduct Stress-Controlled Tests and Study of the Hydromechanical Behavior of Collapsible Soils under Anisotropic Consolidation Case Study: Loess of Gorgan

Soleymani Borujerdi, Saman | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47361 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Haeri, Mohsen
  7. Abstract:
  8. Collapsible soils such as loess, which are naturally nearly dry or unsaturated, are problematic soils that experience significant decrease in volume when they are subjected to increasing moisture under loading. This type of soils are present in some parts of Iran such as province of Golestan. Most of the researches to date has tended to focus on measuring the values of collapse using conventional double oedometer. However, the study of hydromechanical behavior of this type of soils considering the effect of initial shear stress using unsaturated triaxial device has been rarely investigated by the researchers. The study on the unsaturated behavior of collapsible soils has started at Sharif University of Technology since about 10 years ago. In addition to manufacturing a number of unsaturated oedometers, an ordinary triaxial device was enhanced and upgraded to a fully automated unsaturated triaxial device with the ability of controlling and recording the test data. The purpose of this investigation as a part of a comprehensive study, in which a number of M.Sc. and Ph.D. students have worked and still are working is to improve the existing triaxial device to an unsaturated stress-controlled apparatus with the ability of conducting anisotropic unsaturated consolidation tests including wetting process in order to study the effect of initial shear stress on hydromechanical behavior of collapsible soils especially Gorgan loess. To evaluate the performance of the developed device, two sets of tests under different stress paths of isotropic and anisotropic stresses were carried out on undisturbed and reconstituted specimens and the results are compared to the findings of tests conducted by former researchers on this type of soil, including strain-controlled tests under different stress paths. The improvement of apparatus for stress control has been very difficult, complex and time consuming in a way that some of the issues have not been solved yet. Nevertheless, because of prolongation of the improving operations, a few experiments were conducted to examine its performance that are not very conclusive. Therefore some more experiments are required for comprehensive identification of unsaturated behavior of Gorgan loess under anisotropic consolidation
  9. Keywords:
  10. Collapsible Soils ; Loess Soil ; Initial Static Shear Stress ; Anisotropic Consolidation ; Hydromechanical Behavior ; Unsaturated Triaxial Device

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