This paper investigates the axial load transfer during seismic events for pile groups installed in loose and dense sand layers. The analysis was conducted employing three-dimensional (3D) nonlinear finite element models (FEM) that were validated using the results from shaking table tests of a model superstructure supported by a pile group installed in saturated (liquefiable) and dry (non-liquefiable) soil profiles. The FEM was employed to explore the axial load transfer at the liquefiable and non-liquefiable tests. The results of the liquefiable test demonstrated that the excess pore water pressure and associated liquefaction during the shaking caused dramatic decrease in the shaft friction resistance. Nonetheless, positive shaft friction was observed through the loose sand layer until the soil becomes fully liquefied. In addition, the end bearing forces decreased dramatically, and the pile exhibited excessive settlement, which mobilized additional end bearing resistance. At the non-liquefiable test, the pile experienced compression and tension loading cycles, but the loads were less than its static capacity. The effects of ground motion intensity, pile diameter, and thickness of the loose sand layer on the load transfer mechanism were also evaluated. It was found that as the pile diameter increased, higher excess pore water pressure developed in the dense sand, which reduced the bearing pressure. Also, as expected, the reduction in shaft resistance was higher as the thickness of the loose (liquefiable) sand layer increased, especially for piles with a small diameter. For the non-liquefiable soil, the strain in the soil increased for larger pile diameters, and consequently, the bearing forces decreased but later increased as the pile settlement mobilized higher resistance.

本文研究了安装在松散密实砂层中的桩组在地震事件期间的轴向荷载传递。使用三维 (3D) 非线性有限元模型 (FEM) 进行分析，该模型使用由安装在饱和（可液化）和干燥（不可液化）中的桩组支撑的模型上部结构的振动台试验结果进行验证土壤剖面。有限元法用于探索可液化和不可液化试验中的轴向载荷传递。液化试验的结果表明，振动过程中的超孔隙水压力和相关的液化导致轴摩擦阻力急剧下降。尽管如此，通过松散的沙层观察到轴正摩擦，直到土壤完全液化。此外，端部承载力急剧下降，桩表现出过度沉降，从而调动了额外的端部承载力。在不可液化试验中，桩经历了压缩和拉伸载荷循环，但载荷小于其静态承载力。还评估了地震动强度、桩径和松散砂层厚度对荷载传递机制的影响。结果表明，随着桩径的增加，致密砂土中产生的超孔隙水压力升高，从而降低了承载压力。此外，正如预期的那样，随着松散（可液化）砂层厚度的增加，竖井阻力的降低幅度更大，尤其是对于小直径桩。对于不可液化的土壤，土壤中的应变随着桩径的增大而增加，因此，