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Padash, Hadi | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44261 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Haeri, Mohsen
  7. Abstract:
  8. During the past earthquakes in all over the world, the piles have had serious damages in soils with liquefaction potential. During an earthquake, liquefaction occurs in some parts of ground with mild slope and saturated and soft granular soil. Afterwards lateral spreading induced by liquefaction incurs irreparable damages on structures and piles particularly. Observing these damages, the researchers and engineers have conducted more surveys and investigations to studying the behavior of piles in granular soils with liquefaction potential and also interactions between  soil  and pile.  In  these  researches,  they have  modeled  the  interactions between  soil  and pile.  However  there are ambiguities in these surveys that require more observations. Of course, it is necessary to providing solutions for reducing the effects caused by liquefaction on piles and structures that constructed on saturated and soft granular soils. In this research, the effect of lateral spreading on piles is simulated by physical modeling of large scale shaking table test. Also, in order to reduce the effects caused by liquefaction and the lateral spreading, implementation of stone  column  and  micro‐pile  in  upstream  and  downstream  of  pile  group  are  analyzed  and  evaluated.  In  this  physical modeling, a pile group 3×3 of polyethylene (HPDE) with high flexibility is used. Also, the soil profile in the model  is  consist  of  three  layers:  dense  and  lower  non‐liquefacted  soils,  the  saturated  granular  layer  with  liquefaction potential and relative density of 15%, and non‐liquefacted surface layer that their slope is 4 degrees. Stimulating the input will be with maximum acceleration amplitude of 0.3 g and dominant frequency of 3 Hz along lateral spreading. According  to  the  experimental  results,  maximum  excess  pore  water  pressure  happens  before  occurance  of  liquefaction, and in this moment the soil acceleration gradually reduces. upon liquefaction and lateral spreading the  soil  displacement  increases  dramaticaly.  However,  reduction  of  rate  of  lateral  spreading  and  movement  of  liquefacted soil from upstream to downstream the soil displacement decreases.as well, at the time of lateral spreading and soil movement from upstream to downstream, tensile stress occurs in the front side of pile group and compressive stress occures in the back side of pile group. Performing micro‐piles in this research did not have considerable  effect  on  the  time  histories  of  acceleration,  pore  water  pressure  and  soil  displacement,  however  stone columns used in upstream and downstream sides of pile group were much more effective.stone columns had  a  remarkable  influence  on  time  histories  of  acceleration,  pore  water  pressure  and  displacement  by  three  effective roles of drainage of excess pore water pressure, compressing and hardening of the soil around the pile also and preventing the movement of liquefacted soil towards downstream
  9. Keywords:
  10. Liquefaction ; Modeling ; Pile Group ; Stone Column ; Lateral Spread

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