Torsional Vibration of a Pipe Pile in Arbitrary Layered Saturated Soil Based on the Additional Mass Model

This study systematically investigates the torsional vibration characteristics of pipe piles embedded in arbitrary layered saturated soils using an additional mass model to account for soil plug effects. A coupled pile‐soil torsional vibration model is developed by integrating Biot's poroelastic theory and the additional mass model, considering viscous damping in both the pile shaft and surrounding soil. Analytical solutions for the torsional dynamic complex impedance at the pile head in the frequency domain are derived using Laplace transforms, separation of variables, and impedance function recursion. The degenerate form of the solution is validated against existing results for solid piles in saturated soils, confirming its accuracy. Parametric analyses are conducted to evaluate the effects of pile geometry, soil properties, and soil plug characteristics on the torsional dynamic stiffness and damping of the pile head, providing insights into the influence mechanisms of key factors in layered saturated soil systems.