A coupled boundary element-finite element solution for pile groups embedded in layered saturated soils under transient loadings

Pile groups in saturated soils frequently encounter transient dynamic loads from earthquakes, waves, and winds. This study uses the coupled boundary element method-finite element method (BEM-FEM) to investigate the transient interaction between pile groups and layered saturated soils. The analytical layer element solution for the stratified saturated soils is used as the kernel function to establish the boundary integral equation of the soils. The pile group is discretized using rod elements on the basis of the finite element theory, and then the dynamic equation of the pile group is constructed. The displacement coordination condition at the pile-soil interface and the boundary condition at the pile cap are introduced to obtain the coupled BEM-FEM equation. The corresponding MATLAB program is developed, whose results are compared with those of numerical simulation by ABAQUS to verify the proposed theory. Further analyses are conducted to discuss the effects of key parameters including the pile-soil stiffness ratio, pile spacing and soil's stratification on the vertical transient response.