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Characterzing Variation of Small Strain Shear Modulus of Unsaturated Sand During Hydraulic Hysteresis with Bender Elements

Shahbazan, Parisa | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48447 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Pak, Ali; Khosravi, Ali
  7. Abstract:
  8. Results of previous studies on silt and clay indicated that variations in the small strain shear modulus, Gmax, during drying had a non-linear increasing trend with matric suction with greater values upon wetting. However, due to different material properties and inter-particle forces, different behaviour in Gmax is expected for sand. Although considerable research has been devoted in recent years to characterize the behaviour of Gmax of sand during drying, rather less attention has been paid to the effect of hydraulic hysteresis on Gmax and its variations during wetting. In the study presented herein, an effort was made to characterize the variation of Gmax for specimens of sand during hydraulic hysteresis. Specifically, the concept of suction stress was used to define trends between Gmax and the effective stress under different loading conditions. In this regard, a series of bender element tests were carried out in a modified triaxial test device with suction-saturation control to evaluate the impact of hydraulic hysteresis and mean net stress on Gmax for unsaturated specimens of sand with different soil size distributions. Trends between Gmax and matric suction for unsaturated sand were found to be different from those for silty specimens. Variations in Gmax showed an up and down trend in both drying and wetting paths, where plotted as a function of matric suction. Results also indicated smaller magnitudes of Gmax upon wetting than those during drying; a behavior attributed to variations in suction stress with matric suction. From the experimental measurements and using the concept of suction stress in unsaturated soils, a semi-empirical equation was developed to predict variations in Gmax along different paths of hydro-mechanical loading
  9. Keywords:
  10. Saturation Degree ; Small Strains ; Hydraulic Hystersis ; Bender Element Test ; Semi Emprical Model ; Maximum Shear Modulus ; Suction Stress

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