Numerical Modeling of liquefaction-induced Settlement of Free Field and Comparison of its Results with Empirical Models

Sadeghi, Habibollah | 2018

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51096 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Pak, Ali
  7. Abstract:
  8. A numerical framework is proposed to estimate the liquefaction-induced settlement of the fully saturated sandy layers in the free fields due to earthquake excitation and the results of the proposed method are compared with those of the empirical or probabilistic methods suggested by the previous researchers. Liquefaction is a sudden transformation of saturated sandy soil into a viscous fluid which is caused by the increase in the pore pressure and decrease in the effective stress and results in the reduction of the shear strength of the soil. One of the most important consequences of liquefaction is the liquefaction induced settlement which has caused severe damages in many places in the world. In this study, a large number of numerical simulations are conducted using Opensees software which employs fully coupled (U-P) formulation to analyze soil displacements and pore water pressures in order to assess the soil volumetric strains and settlement. The constitutive model proposed by Dafalias and Manzari (2004) is employed which is based on the critical state soil mechanics and is capable of modeling the saturated sand behavior under monotonic and cyclic loadings. After the verification of the numerical modeling results using centrifuge experiments, a parametric study was conducted on several parameters such as peak ground acceleration, transverse acceleration ratio, duration and predominant frequency of the earthquake record and the soil relative density. Additionally, two equations were developed based on the numerical modeling results conducted on Nevada sand and by means of probabilistic modeling to estimate the earthquake induced settlement by taking the uncertainty of the model into account. Furthermore, the results of the previous empirical or probabilistic methods were compared with the results of the present study, and their precision were evaluated using a number of case studies. In the last part, the probability of exceedance curves for different relative densities are developed and introduced which can be utilized to estimate the earthquake induced volumetric strain with the desired precision and based on the importance and performance of the structure
  9. Keywords:
  10. Liquefaction ; Numerical Modeling ; Settlement ; Fully Coupled Two-Dimensional Dynamics Analysis ; OpenSees Software ; Free Fields ; Level Ground

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