Horizontal impedance of pile groups considering shear behavior of multilayered soils

The impedances and internal force distributions of a pile and pile groups subjected to horizontal harmonic pile-head loads have been studied. A layered Pasternak model, which overcomes the limitation of the Winkler model, that ignores the shear stiffness of the soil, is developed to describe the reaction of the soil on piles. The differential equation of the horizontal damped vibrations of a pile is solved by the initial parameter method, combined with transfer-matrix formulations, to deal with the layered property of the soil. The superposition approach, based on the interaction factors, is taken to estimate the effects of pile groups. The precision and the applicability of the method are demonstrated through this study. Comparing the results of the Pasternak model and the Winkler model, it is revealed that the role of soil shear has an influence on the impedances of a single pile and pile groups, especially in the case of a low pile–soil modulus ratio.