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Numerical Simulation of Ground Displacement Induced by Lateral Spreading Phenomenon

Ghasemifare, Omid | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41173 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Pak, Ali
  7. Abstract:
  8. The lateral movement of a liquefiable layer on gently slopes is the most visible and devastating type of liquefaction-induced ground failure. Occurrence of liquefaction in sloping ground causes large deformations on ground surface, which may lead to several meters in some cases. Recent earthquakes have shown that this phenomenon causes severe damages to coastal structures, piers of bridges and life-lines, by exerting large lateral forces. In this research, a fully coupled two-dimensional dynamic analysis has been used to simulate the lateral spreading phenomenon and to evaluate the magnitude of deformations occurred in liquefiable soils. The critical state bounding surface elastic-plastic sand model, proposed by Manzari and Dafalias (1997), which possesses the simulative ability of the behavior of drained or undrained saturated sands under monotonic and cyclic loadings, is used, while a fully coupled (u-P) formulation is employed to analyze soil displacements and pore water pressures. Furthermore, in this research, the possibility of variation in the coefficient of permeability for saturated sands has also been implemented to the program. According to this relation, the soil permeability is a function of the excess pore pressure ratio, that varies correspondingly with increase or decrease in the magnitude of pore water pressure. In order to be confident of the accuracy of numerical analysis results, at first two centrifuge experiments in which soil profile has two different slopes, were simulated and the results of numerical analysis compared with experimental measurements. These comparisons showed that the developed numerical model has the capability to simulate the “lateral spreading” phenomenon. Numerical results show that the most part of soil settlement and lateral displacement are occurred during earthquake loading. After getting confidence of the accuracy of the results, this model has been used for a comprehensive parametric study. In parametric analyses, different factors such as ground slope, thickness of liquefiable layer, relative density of liquefiable layer, maximum acceleration of dynamic loading, frequency of input motion, number of load cycles (duration of dynamic loading) have been studied and their effect on magnitude of soil deformations and generated excess pore water pressure have been precisely studied. The generated deformations in two different slope profiles: a dry sand layer and a liquefiable sand layer under dynamic loading are also compared. At the end, an equation for prediction of maximum lateral displacement has been presented. Comparison of this equation with experimental results and other empirical relations shows the proficiency of this equation to other similar relations
  9. Keywords:
  10. Liquefaction ; Excess Pore Water Pressure ; Lateral Spread ; Lateral Displacement ; Fully Coupled Two-Dimensional Dynamics Analysis

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