Effects of Separation on the Behavior of Soil-Pile Interaction in Liquefiable Soils

Separation and sliding between soil and pile have a significant effect on the complex behavior of pile groups under dynamic condition. In addition to separation between soil and pile, the behavior of soil medium surrounding the piles is nonlinear during strong excitations. Therefore, soil is modeled using a nonlinear work-hardening plastic cap model. Because of shaking, there is an increase in pore water pressure. To simulate it, the pore-pressure generation capability is added in modeling the behavior of the soil medium. A full three-dimensional finite-element soil-pile model has been developed with approximate radiation condition at infinity simulated by frequency dependent Kelvin elements. The model and the process of computation have been verified with the established literature. The effects of separation on the dynamic stiffness and seismic response of single pile and pile groups have been examined considering work-hardening soil-plasticity without and with pore-pressure generation capability for a wide range of frequencies of excitation. Real-time earthquake motions are also applied and the effects of separation on the responses of pile groups are investigated. Significant effects of separation of the soil medium on the response of the soil-pile system have been observed and approximately quantified. (c) 2012 American Society of Civil Engineers.