Interaction of a pile with layered-soil under vertical excitations: field experiments versus numerical simulations

Abstract

Data recorded during a field test involving an instrumented drilled shaft under vertical excitations are examined in order to (1) extract the soil–pile system’s dynamic impedance, and (2) to evaluate the small-strain shear stiffness and material damping properties of the surrounding soil. Numerical simulations of steady-state vibration tests with an axisymmetric finite element model are used for back-calculating the in-situ small-strain dynamic soil properties (i.e., shear stiffness and material damping ratio). Also, a numerically computed impedance function is compared with known analytical solutions and that obtained through direct processing of the field test data. These analyses revealed that the discrete numerical model can successfully reproduce the measured responses of the shaft-soil system, and yield its frequency-dependent impedance function as well as equivalent small-strain dynamic soil properties. The validated numerical model presented here offers a detailed view of the vertical dynamic responses of drilled shafts within the small-strain range, and can be used for design and analysis of future field tests.