NONLINEAR FIELD RESPONSE OF PILES UNDER HORIZONTAL HARMONIC EXCITATIONS

Abstract

Harmonic excitation of pile foundation is a typical dynamic phenomenon occur during machine vibration. In many cases, it has been found that the horizontal excitations are the critical ones which governs the design for machine-based pile foundations. In order to comprehend the horizontal frequency-amplitude responses of pile foundation under various harmonic excitation forces, forced vibration tests on several sets of small-scale single and pile groups have been carried out. According to the test results, there are two resonant peaks within the operational frequency range shown by the dynamic frequency-amplitude responses, where the first peak is found to be more dominant as compared to the second peak. Additionally, as resonant frequencies are lowered and resonant amplitudes grow for an increase in excitation forces, the response curves demonstrate the nonlinear patterns of pile groups. The basic dynamic characteristics of all soil-pile setups are found to be similar to each other. As the group's pile count increases, the resonant frequency values increase while the resonant amplitude values decrease, increasing the dynamic stiffness of the soil-pile systems. The resonant amplitude for the first peak of 2х2, 2х3, and 3х3-pile groups are found to be approximately 13%, 36% and 79% lower, respectively, as contrasted with the single pile under the same dynamic load.