Boundary Effect on the Seismic Response of a Three-dimensional Soil Slope with a Shallow Foundation on Top

Numerical approaches are providing a versatile environment for conducting the studies of slopes and shallow foundations on the top of slopes. However, there are few studies for assessing the boundary effects on the seismic response of a soil slope and the dynamic behaviors of a shallow foundation on top of three-dimensional (3D) slopes. On the basis of a systematic parametric study, Finite Element (FE) simulations are firstly conducted to evaluate the boundary effect on the seismic performance of the soil slope. Then, the boundary effects on the behaviors of a shallow foundation on top of a 3D slope under the earthquake loadings are addressed. The results show that for a given 3D soil slope, fixing the displacement degrees of freedom only in the y-direction (perpendicular to the shaking direction) at the lateral boundaries is inappropriate, because this approach does not consider the 3D effect. A smaller slope’s width/height ratio is obtained for stiffer soil, compared to soft soil, as the 3D effects induced by the lateral boundaries lose significance. The earthquake characteristics (peak ground accelerations and frequency content) play important roles in the differences among the three lateral boundaries. Furthermore, when the boundary extent along the y-direction is increased, the foundation settlement that is controlled by the applied pressure and earthquake loading together, will be mostly affected by the seismic excitation. Overall, the conducted study highlights the significance of boundary conditions on the seismic responses of soil slopes and a shallow foundation on the top of it and can be helpful for engineers to choose an appropriate boundary in numerical analysis.