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Evaluation Of The Effects Of Degree Of Saturation And Suction On Dynamic Properties Of Sand: Experimental Study On Babolsar Sand

Ahmadinezhad, Adel | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53461 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Jafarzadeh, Fardin
  7. Abstract:
  8. The ground experiences various hydraulic conditions under climate and groundwater level changes, and it becomes dry or wet frequently. The states of pore-water within the geomaterial, being signified in terms of suction and saturation degree, change during these variations, and consequently affect the soil behavior. In the course of isotropic or anisotropic dynamic loading on soil deposits, the altered hydraulic conditions can lead to different responses. Systematic investigation of these effects with element laboratory tests on a poorly graded sand is the main objective of the current study. Therefore, the dynamic response of sand in terms of dynamic properties (i.e. shear modulus, damping ratio, dynamic volumetric changes, elasticity modulus, Poisson's ratio, and body waves velocity) was studied at different values of suction, saturation degree, compaction water content, principal stresses direction, and intermediate stress parameter. Initially, the limitations of the laboratory apparatus used were eliminated to meet the research goals. On the one hand, the cyclic simple shear apparatus was developed to conduct suction-controlled testing over a wide range of shear strains. On the other hand, to perform suction control/measurement tests on granular material, the cyclic hollow cylinder apparatus was modified. The results of laboratory experiments are presented from several perspectives: 1) Effects of suction, saturation degree, and hydraulic path (hydraulic hysteresis) on dynamic parameters at different values of shear strain amplitude by using the developed cyclic simple shear apparatus, 2) Impacts of dynamic effective density on elastic modules determined by body wave velocities, 3) Interaction effects of induced anisotropic, suction, and compaction water content on dynamic properties of unsaturated sand by using the modified cyclic hollow cylinder apparatus. The impacts of the Effective Dynamic Density of sand on the wave velocity analysis, for determination of soil elastic modulus are revealed in this study for the first time. Furthermore, it is shown that the effects of hydraulic hysteresis on the changing trend of the parameters studied in this research are revealed in different ways like changing in extrema. In addition to known mechanisms including hydraulic hardening, suction stress, disappearance of water meniscus at high suctions, and pore water pressure at high saturation degrees for interpretation of the results, the lubrication mechanism between particles was introduced and used. Then, experimental relationships were proposed to estimate the effects of induced anisotropy on shear modulus, damping ratio, and dynamic volume change. Finally, the study of the effects of suction and degree of saturation on the induced anisotropy dynamic properties showed that depending on interparticle movements, the effects of suction and saturation degree can also be anisotropic
  9. Keywords:
  10. Cyclic Simple Shear ; Suction ; Saturation Degree ; Shear Modulus ; Damping Ratio ; Babolsar Sand ; Cyclic Hollow Cylinder

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