3-Dimensional Numerical Modelling of Pile Group Response to Liquefaction-induced Lateral Spreading

In this paper, a 3D coupled soil-water finite element analysis is employed to simulate the behavior of a pile group subjected to liquefaction-induced lateral spreading. The results demonstrate that the numerical model can satisfactorily simulate the response of soil including its accelerations, excess pore water pressures and displacements as well as that of the piles including displacements and bending moments. Time histories of excess pore water pressure show that liquefaction in free field soil begins at the initial stages of shaking and upon liquefaction, the amplitude of soil acceleration decreases. The maximum lateral displacement of ground is observed at the regions far from the piles. In contrary, the extent of ground displacement decreases in areas close to the piles. The numerical model was able to predict the bending moment profiles in piles and particularly their maximum values. The maximum negative bending moments occur nearby the pile cap while their maximum positive values are observed at the base of the piles. Moreover, the maximum bending moment in downslope piles of the group is about 70% greater than that in upslope one. The results of the parametric study show that the displacement of piles and the bending moment in them decrease with increasing either the flexural stiffness of piles or the relative density of the sand. Also, it is revealed that the amplitude of input acceleration is the most influencing factor affecting the pile response as increasing it by a factor of 3.5 induces 3.6 times greater bending moments in piles.