Abstract Although the parallel seismic (PS) method has been successfully applied to determine the unknown foundation depth of buildings and bridges, the ability to detect defects in pile foundations has not been verified. In this paper, three large-scale model piles with artificial defects are designed and constructed in multilayered ground. The capability of cross-hole sonic logging, low-strain pile integrity testing and PS method to detect the defects of pile foundation is compared. The effects of the pile-to-borehole distance and the excitation position on the stress wave transmission are analyzed in detail. Finally, the abnormal characteristics of stress waves corresponding to different types of defects are summarized. The results show that pile defects affect the difference in the stress wave impedance by the PS test, and the features of the first arrival waves can reflect the type of defect. When the distance between the borehole and pile is within 0.5 m, the wave form and amplitude of the first arrival waves can be used to distinguish the defects of necking, breaking and sedimentation. Increasing the pile-to-borehole distance by more than 1 m is not conducive to identifying defects. When the pile defect position is close to the side of the shortest path of stress wave transmission, the abnormal characteristics of the first arrival waves are much clearer than when the defect position is far from the side; otherwise, the feature of the defects will be greatly weakened.

中文翻译：

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用平行地震法检测桩身缺陷的大型模型试验

摘要 虽然平行地震（PS）方法已成功应用于确定建筑物和桥梁的未知基础深度，但检测桩基缺陷的能力尚未得到验证。在本文中，在多层地基中设计并建造了三个具有人工缺陷的大型模型桩。比较了跨孔声波测井、低应变桩完整性测试和PS法检测桩基缺陷的能力。详细分析了桩孔距离和激励位置对应力波传输的影响。最后总结了不同类型缺陷对应的应力波异常特征。结果表明，桩身缺陷影响应力波阻抗差异的PS试验，初至波的特征可以反映缺陷的类型。当钻孔与桩距在0.5m以内时，可利用初至波的波形和幅度来区分颈缩、破碎和沉积等缺陷。桩距增加1m以上不利于缺陷识别。当桩身缺陷位置靠近应力波传播最短路径的一侧时，初至波的异常特征比缺陷位置远离一侧时明显；否则，缺陷的特征将被大大削弱。初至波的波形和振幅可用于区分颈缩、破碎和沉降等缺陷。桩距增加1m以上不利于缺陷识别。当桩缺陷位置靠近应力波传播最短路径的一侧时，初到波的异常特征比缺陷位置远离一侧时明显；否则，缺陷的特征将被大大削弱。初至波的波形和振幅可用于区分颈缩、破碎和沉降等缺陷。桩距增加1m以上不利于缺陷识别。当桩缺陷位置靠近应力波传播最短路径的一侧时，初到波的异常特征比缺陷位置远离一侧时明显；否则，缺陷的特征将被大大削弱。初至波的异常特征比缺陷位置远离侧面时更清晰；否则，缺陷的特征将被大大削弱。初至波的异常特征比缺陷位置远离侧面时更清晰；否则，缺陷的特征将被大大削弱。