Dynamic Response of Pile Reinforced Soils and Piled Foundations

The rigid-pile soil-improvement technique aims to increase the bearing capacity of the soil and decrease the settlement of the surface structure. The most remarkable difference of this technique from the deep-foundation system is the soil layer between the pile heads and the structure. This soil layer, called the mattress, is made of compacted granular materials and participates in the load transfer through arching and shear mechanisms. In order to understand the dynamic behavior of rigid-pile reinforced soils, tri-dimensional finite-element analyses of a soil-pile-slab system, a soil-pile-mattress-slab system, and a soil-pile-mattress-embankment system are presented in this paper. Different geometric configurations are studied in terms of dynamic impedances. The soil, piles, mattress, and embankment are represented as continuum solids, and the slab is represented by structural plate-type elements. The horizontal and vertical impedances of pile foundations are presented and the results are compared with studies in the literature. This study shows the influence of the mattress stiffness, the geometrical configuration, and head/tip fixity conditions on the dynamic response of the foundation system. A comparison between rigid piles and pile foundations is then presented.