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Seismic response of waterfront structures on liquefiable soil

Nonlinear effective stress analyses are conducted to evaluate the response of port infrastructure especially caisson-type quay walls against seismic loads. Since cohesionless soil is a key material encountered in many water front structures, liquefaction is considered an important factor affecting the stability of these structures. An existing constitutive model for granular soils (Manzari-Dafalias) is selected to simulate the essential features of stress-strain-strength behavior of cohesionless soils. The model is modified to add new features such as the hystertetic behavior in cyclic loading at small strain levels and the effects of fabric evolution on volumetric as well as deviatoric response of the soil. The modified model is then implemented in a finite element analysis code and a number of finite element simulations are performed to investigate the seismic response of a quay wall founded on liquefiable soil. The selected quay wall is part of a centrifuge model constructed to mimic the main features of waterfront structures in major ports. The computational results including displacement, acceleration, excess pore water pressure, and stress time histories at different locations within the selected system were compared with the results of the centrifuge experiment. One important aspect of this investigation is to determine the accuracy and robustness of the numerical simulation in predicting the potential occurrence of liquefaction in the seabed and/or backfill soil and to estimate the seaward displacement and possible tilting of the quay wall due to severe ground shaking. Comparison between numerical simulation results and those obtained from existing experimental data shows that advanced numerical/constitutive modeling techniques used (and further developed) in this research are able to predict the behavior of granular soils and the response of waterfront structure under seismic loads. However, since the experimental data is related to a simplified model of quay walls, it is necessary to design a more detailed and realistic experimental model and further assess the validity of the constitutive/numerical modeling technique by comparing the numerical simulation results with the results obtained from the new experiments.

Author(s):

Morteza Rahimi Abkenar    
George Washington University
United States

Majid Manzari    
George Washington University
United States