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The Physical Modeling and Analysis of Seismic Soil-Pile Interaction in Unsaturated Sand Using Geotechincal Centrifuge

Ghadirianniari, Sahar | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49752 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khosravi, Ali
  7. Abstract:
  8. The seismic behavior of pile-supported systems has been an active area of research over the past decades. However, focus has mostly been on evaluating the seismic response of structures embedded in either dry or fully saturated, especially liquefying soil conditions. In this study, a series of dynamic centrifuge tests have been conducted to investigate the effects of soil’s degree of saturation on the seismic behavior of pile-supported superstructures. The scaled physical model tests were carried out on two distinct pile-mass systems embedded in uniform sand layers. A steady state infiltration technique was used to control matric suction profiles in the sand layer prior to shaking. The obtained results from these experiments were illustrated in terms of acceleration and displacement time histories, peak acceleration amplification factors, peak displacement amplification factors, frequency content of the structural motion, and soil surface settlements. The observed response showed higher acceleration amplification and lower lateral deformation for the pile-supported systems with foundations embedded in unsaturated sand comparing with those the ones in dry sand. The variation of the above-mentioned parameters with degree of saturation (in the studied range of saturation degree) showed maximum acceleration amplification factors, minimum lateral displacement amplification factors and mimimun settlement values for mid-range saturation degrees (0.2-0.4) The observed response was explained by the higher shear modulus and lower damping of unsaturated sand as compared to dry sand. An inverse simple pseudo-static analysis was performed to back-calculate soil modulus values from pile lateral deformations. The calculated values of soil modulus were higher for unsaturated sands showing consistency with the effect of matric suction on increasing soil stiffness
  9. Keywords:
  10. Centrifuges ; Soil-Pile Interaction ; Unsaturated Soil ; Physical Model Test ; Granular Soil ; Steady State Infiltration Technique

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