Numerical analysis of liquefaction-induced differential settlement of shallow foundations on an island slope

Seismic differential settlement of shallow foundations on an island slope with a liquefiable sand stratum can significantly reduce the foundation's bearing capacity. Now, most studies focused on the settlement of foundation, while few efforts have provided a description of the differential settlement of foundation. In this study, we therefore adopted an approach using three-dimensional (3D) nonlinear finite element (FE) simulation. A special case that the water table located at the interface between the liquefiable sand layer and the clay layer was employed in this model. A series of parametric studies involving soil properties, surcharge load, foundation location, and the typical shaking characteristics of earthquake events were conducted to identify their impact on liquefaction-induced differential settlement. Generally, a more permeable sand stratum and a larger cohesion of the upper clay stratum were found effective at decreasing differential settlement. A foundation's length/width ratio also played an important role in reducing differential settlement and, when the distance of the foundation from the crest of an island slope reached a critical value, the differential settlement tends towards a steady value. Heavily-loaded shallow foundations resulted in more differential settlement, leading to a reduction in their seismic bearing capacity. The peak ground acceleration and Arias intensity of an earthquake had a significant effect as well. In addition, some preliminary design considerations for shallow foundation under the earthquakes were proposed. Overall, the numerical results offer some valuable references to improve the design and construction of foundations on an island slope under the seismic loadings.