Abstract: X-section cast-in-place concrete pile (X-section pile) is a kind of new special-shaped pile. Considering the distribution of dynamic friction resistance on concave arc section, convex arc section and soil-pile coupled vibration, treating the soil as axisymmetric homogeneous viscoelastic medium, the analytical solution in frequency domain is obtained by using Laplace transformation technique and coordinate transformation. The solution is compared with that of solid circular pile to verify the rationality. Moreover, by analyzing the effect of pile length, open arc spacing and open arc angle on complex dynamic stiffness and velocity admittance, the influence of dimension parameters on the vertical vibration characteristics of X-section pile is investigated. It shows that the complex dynamic stiffness at the top of pile increases, the oscillation amplitudes and resonant frequencies of the velocity admittance curves significantly decrease with the increase of pile length. The open arc spacing and open arc angle have little influence on the velocity admittance at low frequencies. At high frequencies, the velocity admittance decreases with the increase of open arc spacing and increases with the increase of open arc angle. However, oscillation amplitudes of the velocity admittance curves increase with the increase of open arc spacing and decrease with the increase of open arc angle.

Key words: X-section pile, vertical vibration, viscoelastic soil, analytical solution, complex dynamic stiffness