Dynamic response of saturated layered soil around defective piles and its application in engineering testing

Abstract

The parallel seismic (PS) method has been increasingly used for non-destructive test, especially for existing piles with superstructures. Nevertheless, there still remains a significant gap in the analytical studies on the dynamic behavior of saturated soils excited by a vertically vibrating pile, which is the essence of the interpretation of the PS test results. In this study, a defective pile-porous fictitious soil pile (PFSP)-saturated layered soil coupled system is proposed in this regard to obtain the dynamic response of fully-saturated soil around and beneath the pile. The semi-analytical solutions are first resolved based on Biot's theory of wave propagation in saturated porous media and are then verified by existing solutions under different degenerated situations. The validated model and solutions are employed to investigate the wave propagation mechanism amid the fully-saturated soil. The time-depth analysis indicates that the vertical vibration of the soil skeleton is governed by the shear wave and the dynamic response of pore pressure propagation is controlled by the fast longitudinal wave. In addition, the vertical responses of the saturated layered soils around a defective pile are basically consistent with that observed in viscoelastic soils, while the excess pore pressure is significantly influenced by the pile defects and the pile-soil stiffness ratio. The conclusions derived from this study can provide valuable insights and practical guidance for conducting pile integrity test (PIT) in saturated soil sites.