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Assessing the Hydro-Mechanical Behavior of Undisturbed Collapsible Soils by Conducting Unsaturated Odeometer Tests Case Study: Northeastern Loess of Golestan Province

Tavasoli, Iman | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52292 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Haeri, Mohsen
  7. Abstract:
  8. The deposits in many regions in Iran, particularly eastern zones like Golestan, Semnan, Yazd, Kerman, Hormozgan, Sistan and Baluchestan provinces consist of deposits of loess, which are categorized as collapsible soils. This kind of soil show sufficient shear strength and low deformability in dry or natural condition. However, if a structure is built on the soil and water seeps or infiltrates into the soil due to several reasons such as sewer leakage, water seepage or heavy precipitations in a way that its moisture reaches to a critical value, the interparticle bonds may break or the present suction in the soil may decrease in a way that the soil experiences sudden collapse, which may result in damaging the structure. In this research, the hydro-mechanical behavior of the Northeastern Loess of Golestan Province is studied using two modified unsaturated oedometer apparatus with the capability of controlling matric suction which had been designed and developed at Sharif University of Technology. Oedometer tests have been performed on undisturbed specimens under K0 condition and under two separate stress paths: constant matric suction and varying vertical net stress (loading and unloading) and constant vertical net stress and varying matric suction (wetting and drying cycles). In these tests, the matric suction, volumetric water content, and vertical deformation of the samples have been controlled and recorded. The results reveal the significant influence of the stress paths on both volumetric behavior and water content of the samples. The soil water retention curve also is affected by the path as well as the value of applied stress. Evaluating parameters of the tested soil by implementing the unsaturated soil models indicates that these models do not predict the collapsible behavior of the soil properly, except for the model presented by Haeri for Gorgan Loesses that could be useful for the soil we studied
  9. Keywords:
  10. Collapsible Soils ; Loess Soil ; Soil Mechanics ; Undisturbed Soil Sample ; Unsaturated Odometer Test ; Constitutive Model ; Unsaturated Soil

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