Simplified model of defective pile-soil interaction considering three-dimensional effect and application to integrity testing

A new simplified model for defective pile-soil interaction (DPSI) is developed to account for the threedimensional (3D) effect in the pile integrity test (PIT) for large diameter piles. To account for the 3D effect, the defective pile is treated as linear continuum rather than the conventional 1D rod model. The surrounding soil is simulated employing the classical plane strain model and the soil resistance at the pile base is represented by the fictitious soil pile model. Theoretical solutions for the velocity field of the defective pile under vertical half sine excitation are derived by integral transformation technique. The developed DPSI model and solutions are then used to investigate the 3D effect in the PIT for defective pile considering four common pile defect types. The obtained results provide important insights into the high-frequency (HF) interferences on the velocity-time history of the defective pile top caused by the 3D effect. Recommendations to minimize the HF interferences in the actual PIT are consequently provided. Application of the DPSI model in interpreting PIT measurements can improve accuracy of pile defect diagnosis.