Numerical Modeling of the Dynamic Behavior of Piles and Pile Groups Due to Liquefaction- Induced Lateral Spreading

Pakzad, Amin | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53930 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Haeri, Mohsen
  7. Abstract:
  8. The phenomenon of lateral spreading occurs as a consequence of earthquakes induced liquefaction in grounds with mild slopes or ending to an opening. This phenomenon has caused many damages to deep foundations and associated structures. Therefore, it is necessary to study and estimate the forces which may be induced by lateral spreading to these structures. Due to the complex mechanism of the effect of lateral spreading on the piles, various tests have been carried out in the form of shaking table as well as centrifuge tests. According to the results of these tests, the forces applied to the piles are significant and can cause crucial damages to deep foundations. On the other hand, because physical modellings are time-consuming and very expensive, the need for numerical research in this field is obvious. According to the limited numerical researches which have been conducted in this area, the power of existing softwares in predicting the behavior of deep foundations under the influence of lateral spreading still should be investigated. Also, by prediction of the behavior of the piles subjected to lateral spreading implementing numerical models, they can be used for parametric study to find the effect of various parameters on the behavior of the piles subjected to lateral spreading, without the need for building physical models for various cases, and therefore time and money is saved.In this study, it has been attempted to predict the behavior of single and group piles subjected to liquefaction induced lateral spreading by numerical modeling. The present numerical research is based on physical model performed by Haeri et al in 2012 and Haeri et al in 2013 using a large rigid container on a shake table. In order to model the behavior of liquefiable soils, it is necessary to model its behavior appropriately under dynamic loads. In this regard Dafalias and Manzari 2014 constitutive model is implemented in this study. This model has 15 parameters which are calibrated using a series of monotonic and cyclic triaxial tests., OpenSees solver was used in this research to perform numerical modeling, and ABAQUS and GID softwares were linked to OpenSees software by code writing, for pre-processing and post-processing operations, respectively. In this regard, the physical model presented by Haeri et al. 2012 was used to verify the numerical model of this study and predict the behavior of single piles subjected to liquefaction induced lateral spreading. Then the verified model was used to investigate the effect of various parameters such as soil relative density, boundary conditions, slope angle and existence of non-liquefiable layer. According to the results, increasing the relative density results in decreasing the pile moments and with changing the boundary conditions from rigid to laminar, the amount of moments and displacement of the piles increased drastically. It was also observed that by increasing the slope from 1 to 4 degrees the maximum moment applied to the single pile becomes 5 times larger. The presence of a non-liquefiable surface layer will also cause a maximum negative moment near the boundary of the non- liquefiable surface and liquefiable layers. Numerical modeling has also been used in this study to predict the behavior of a 3x3 pile group subjected to liquefaction induced lateral spreading to evaluate the ability of numerical modeling by comparing its results with the results of the experiment of Haeri et al. 2013. The results of the numerical modeling indicate that it can predict the behavior of pile groups subjected to liquefaction induced lateral spreading
  9. Keywords:
  10. Liquefaction ; Parametric Study ; Numerical Modeling ; Pile Group ; Single Pile ; Lateral Spread

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