时域反射法探测桩身缺陷的模型试验研究

Model Tests on Detecting Pile Defects Using Time Domain Reflection Method

为验证时域反射法对桩身缺陷的检测效果,设计了时域反射技术检测桩基完整性的模型试验,分别针对不同介质(空气、干土和湿土)环境中的有缺陷桩和无缺陷桩进行检测,验证时域反射法对于预设缺陷的检测效果,并分析缺陷位置和缺陷数量、桩周介质类型等因素对检测结果的影响。研究结果表明,时域反射法可以用于检测桩身缩颈缺陷,在模型桩缺陷段和桩底位置能获得较清晰的反射信号;电磁波传递过程中发生的衰减、频散、介质不连续等导致电磁波实测波形和理论波形存在差异;不同介质中电磁波的波速变化导致缩颈缺陷探测结果与实际情况存在一定偏差,但误差仍处于实际工程要求的精度范围内。

In order to verify the effect of time domain reflection method on the detection of pile defects,this paper designs a model test of time domain reflection technology to detect the integrity of pile foundation.The model tests of defective piles and normal piles in different media(air,dry soil and wet soil)are carried out to verify the detection effect of time domain reflection method on preset defects,and the influence of defect location,defect quantity and surrounding media are analyzed.The research results show that the time domain reflection method can be used to detect the necking defects of the pile body,and a clear reflection signal can be obtained at the defect section and the position of the pile bottom of the model pile.Due to the attenuation and dispersion of electromagnetic wave when it propagates in the discontinuous medium,the measurement waveform of electromagnetic wave is different from the theoretical waveform;the change of propagation speed of electromagnetic wave in different medium leads to the actual results of the detection results of necking defects and necking defects.However,the error is still within the accuracy required by the actual project.