Dynamic soil-structure interaction modeling using stiffness derived from in-situ Cone Penetration Tests

This paper presents the results of an experimental and numerical investigation into the natural frequency of a pile driven into dense sand. The experimental arrangement involves fitting accelerometers along the pile shaft and using a modal hammer to induce lateral vibration. The natural frequency is obtained by performing Fourier analysis on the acceleration signals. A numerical model is developed that models the pile as a beam supported by lateral springs. The natural frequency is obtained by performing an eigenvalue analysis in the numerical model. The spring stiffness is derived by first obtaining the G0 value for the sand at the installation location. This is achieved using the rigidity index, a correlation between the cone tip resistance qc value and the small-strain shear modulus G0. The G0 value is converted to lateral spring stiffness values using an equation derived analytically from the beam on an elastic foundation case. Good agreement is observed between the experimentally measured natural frequency and that which is calculated from the numerical model. This research paves the way for more accurate assessments of dynamic soil-structure interaction, and can be particularly useful in the design of structures that are dynamically sensitive such as wind turbines.