Effects of uncertainties of soil and pile mechanical properties on the dynamic stiffness of deep foundations in homogenous deposits

In the soil-structure interaction framework, among the results of the soil-foundation system analysis (kinematic analysis) the dynamic impedance functions represent the force-displacement relationships of the compliant restraint for the superstructure. The intrinsic varia-bility of soil parameters and of design materials represents an uncertainty source which is nec-essary to include in the definition of the soil-foundation model, in order to predict the super-structure response adequately. The aim of this work is to evaluate effects of uncertainties on soil dynamic and mechanical properties on the impedance matrix of single piles in homogeneous soils, focusing on the sensitivity of the parameters. A Quasi Monte Carlo (QMC) simulation with sampling based on Sobol’ sequence is performed starting from the probabilistic distribu-tion of three main parameters characterizing the soil-piles response, i.e. the soil density, the shear waves velocity and the concrete elastic modulus of piles, available from the literature. The analyses are carried out through the numerical model developed by the Authors and a sen-sitivity study on the optimal number of simulations is performed, comparing the use of Quasi-random sampling with the classical Monte Carlo simulation technique. Moreover, results of sensitivity studies show the influence of variability of each considered mechanical parameter on the global response of the soil-foundation system.