Impedance Functions of Slab Foundations with Rigid Piles

The earthquake resistant design of structures depends upon the soil-structure interaction during seismic excitation. The dynamic behavior of surface foundations and deep foundations has been investigated by several authors (Gazetas in Soil Dyn Earthq Eng 2(1):2–42, 1983; Pecker in Dynamique des sols. Presses de l’Ecole Nationale des Ponts et Chaussées, Paris, 1984; Sieffert and Cevaer in Manuel des fonctions d’impédance. Ouest-Editions, Nantes, 1992, etc.) but the dynamic behavior of pile-reinforced soils has not been sufficiently studied yet. The design of pile-reinforced soils comprises the design of the rigid piles and the design of the earth-platform. The foundation system studied in this article consists of an earth-platform over a soft ground reinforced by deep piles. In order to understand the dynamic behavior of a rigid pile, a series of dynamic tests is conducted on an experimental site. The vertical and horizontal impedances of the slab foundation are obtained with and without rigid piles. The numerical models are developed to interpret these dynamic tests. The numerical and experimental impedance functions are compared in both the vertical and the horizontal directions. A sensitivity analysis on the influence of the physical and geometrical properties of rigid piles on the impedance functions is presented.