Horizontal and rotational impedances for radially inhomogeneous soil media

Soil reaction to harmonic motion of a rigid central hole is studied in terms of linear viscoelasticity. Horizontal and rotational dynamic impedances of a radially inhomogeneous soil layer with a circular hole are formulated considering a continuous, radial variation for the complex shear modulus of the material. The impedances are evaluated over a wide range of parameters and compared with those obtained from other solutions. These impedances can be used to predict the dynamic response of bodies embedded in soil that account for soil radial inhomogeneity. The influence of strengthening the soil adjacent to the foundation on the impedance functions is studied. The effect of Poisson's ratio is examined. Furthermore, the effect of the increase in the shear modulus and the width of the improved zone is investigated. It was found that these parameters should be chosen according to the range of frequency of the expected excitation.