Abstract Summary
Pile foundations are commonly used to support the superstructures of bridges, buildings and heavy industrial plants. The determination of pile stiffness and damping is an important step in the analysis of the soil-structure-interaction of pile-supported structures subjected to dynamic loading due to earthquakes, machinery, seawaves, etc. To date, impedance functions for different types of soil-foundation systems are typically available from analytical, semi-analytical and numerical approaches. The finite element method (FEM) with viscous boundaries consisting of dashpots has gained the most popularity among the numerical methods. However, this numerical approach generally requires large bounded domains for satisfactory accuracy, since viscous boundaries absorb only plane waves propagating perpendicularly to the artificial boundary. Moreover, very few numerical studies in which impedance functions for pile foundations are computed, are validated with experimental data, since field validation studies for deep foundations are very limited. In the present paper the three-dimensional dynamic interaction of pile foundation in layered soil and the accompanied response of the pile foundation on the free field excitation are investigated by means of numerical and experimental studies. To this end, a three-dimensional FE numerical scheme with efficient absorbing layers is developed to simulate the interaction of piles with layered soils in frequency domain. In the FE solver the Perfectly Matched Layer (PML) technique is successfully implemented and the waves propagating outward from the bounded region are attenuated and absorbed. Results of the new developed FE-PML numerical scheme are verified against numerical and experimental results. The numerical results for the verification of the FE-PML model are obtained by means of the SC-SASSI Software based on exact analytical solutions (Green’s functions) for dynamic loads in layered structures, while the experimental validation is conducted by means of vibration measurements on pile foundations. First, a single pile in a homogeneous viscoelastic half-space is modelled and the computed impedance functions are verified with analytical solutions. Next, the influence of the wave propagation through the pile foundation is modelled and validated through vibration measurements. Both the numerical simulation and the in situ measurement results exhibit a reduction of the vibration amplitude due to the piles and this reduction strongly depends on their stiffness. All simulation results demonstrate the ability of the developed FE/PML numerical tool to study the dynamic interaction of piles in layerd soils and to provide better insights into wave propagation patterns within highly heterogeneous soil media.
