LATERAL VIBRATION OF PILE GROUPS IN VISCOELASTIC SOIL LAYER DESCRIBED BY FRACTIONAL DERIVATIVE OPERATOR

The soil around piles is regarded as viscoelastic medium and the mechanical properties are described by fractional viscoelastic model. Based on the Novak plane strain hypothesis, the attenuation function of horizontal displacement and the stiffness and damping coefficient of the soil layer described by fractional viscoelastic model were obtained by potential functions and boundary conditions. The pile-soil dynamic interaction was modeled by Winkler dynamic elastic-damping model, the pile to pile dynamic interaction and horizontal vibration of the pile groups in the soil described by fractional derivative viscoelastic model were solved by initial parameter method. The influence of the order of fractional derivative and model parameter of soil on the pile to pile dynamic interaction and horizontal dynamic impedance of pile groups was investigated through numerical examples. The result indicates that the influence of the order of fractional derivative on the attenuation function of horizontal displacement is related to the pile space and load direction angle; in studying the horizontal dynamic impedance of pile groups, the soil model can be simplified to the cases of classic viscoelastic and elastic; the order of fractional derivative and the model parameter of soil have great effect on the lateral dynamic impedance of the pile groups.