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Collapsible Behavior of Gorgan Loess Using Odeometer

Zamani, Atefeh | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42249 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Haeri, Mohsen
  7. Abstract:
  8. In nature, there are types of soils that when goinging under stress at constant moisture, or increase of moisture at constant stress, or change of both characters, they show a sudden and high level decrease in their volume. These type of soils are named as Collapsible soils. Iran is one of the countries that at some parts of its land collapsible soils are found. In this research by using of laboratory equipments, the volume change behavior of collapsible loess soils of Gorgan plain (North of Iran) is evaluated under increase of water content and inundation stress. In these experiments, the usual odeometer cell has been used for exploring the behaviour of collapsibility and volume change of the loess soil of Gorgan plain. In addition, efforts have been devoted to construct an odeometer cell with the ability of controlling the matric suction to be able to explore these characters with a high degree of prescision, with which different parameters could be evaluated. Three groups of experiments have been performed during this survey. The first group of experiments was performed by usual odeometer and complete collapsibility potential of the undisturbed samples of the loess at vertical inundation stresses of 2, 4, 8 and 16 kg/cm2 were examined and obtained. The second group of experiments was performed on the reconstructed loess soil at a dry density equivalent to the mean dry density of the undisturbed soil. In these tests the complete collapsibility potential, similar to the experiments on undisturbed samples were examined and obtained. The third group of experiments was conducted by use of odeometer with the ability to control suction. For this aim, this instrument was built and calibrated. Some efforts were also done to perform a number of experiments to evaluate the volume change of the loess relative to the matric suction changes. According to the results of first and second group of tests, it can be suggested that this soil is in the category of soils with high collapsibility potential. In addition, similarities or dissimilarities of the results of experiments on undisturbed and reconstructed soil samples were evaluated and the results were discussed. The results show that collapsibility potential decreases with increase in initial moisture content of both reconstructed and undisturbed samples.The change of collapsibility potential with increasing inundation stress is a function of initial moisture content of the samples
  9. Keywords:
  10. Loess Soil ; Unsaturated Soil ; Matric Suction ; Collapsible Soils

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