Soil-Pile-Structure Interaction Effects in Alluvium with Non-constant Shear Modulus in Depth

Abstract

This study developed a simple analytical model to evaluate soil-pile-structure interaction effects on the alluvium with non-constant shear modulus in depth. Numerical analysis was performed to verify the accuracy of the proposed analytical model. A good agreement between analytical and the numerical results evidenced the accuracy of the proposed analytical model. Two systems were compared analytically: case A—single degree-of-freedom (SDOF) system located on a pile in a soil layer with constant shear modulus in depth; case B—SDOF system located on a pile in a soil layer with a non-constant shear modulus in depth. The results showed that for case B, soil-structure interaction effects on structures located on soil alluvium with a non-constant shear modulus in depth were more significant, similar to those of the SDOF system located on softer soil. In case B, the shear modulus of soil near the surface of the layer was lower than the depth soil, and the degree of freedom at the pile head was more flexible (rocking DOF), which increased the vibration period of the system at least 8%. Hence, dynamic behaviors of tall and heavy structures significantly affected the alluvium with non-constant shear modulus in depth. The assessment of soil-structure interaction is a local issue and for dynamic analysis one should use the shear modulus around the foundation, not the mean value of 30-m depth of soil alluvium.