A new simplified model for defective pile-soil interaction (DPSI) is developed to account for the three-dimensional (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.

针对缺陷桩-土相互作用（DPSI），开发了一种新的简化模型，以解决大直径桩的桩完整性测试（PIT）中的三维（3D）效应。考虑到3D效果，将有缺陷的桩视为线性连续体，而不是常规的1D杆模型。采用经典的平面应变模型对周围土壤进行模拟，并以虚拟土桩模型表示桩基处的土阻力。通过积分变换技术推导了竖向半正弦激励下缺陷桩速度场的理论解。然后，将开发的DPSI模型和解决方案用于考虑四种常见桩缺陷类型的缺陷桩在PIT中的3D效果。获得的结果为3D效应引起的缺陷桩顶速度-时间历史的高频（HF）干扰提供了重要的见解。因此，提出了减少实际PIT中的HF干扰的建议。DPSI模型在解释PIT测量结果中的应用可以提高桩缺陷诊断的准确性。