一种针对岩土工程缺陷检测问题的冲击映像方法及应用研究

An impact imaging method for defect detection and its application in geotechnical engineering

采用各种探测手段揭示目标介质内部构造的信息一直是工程界所关心的重要课题。以弹性波在不同介质交界面传递特性为理论基础,明晰冲击映像检测方法的基本原理。采用有限差分数值模拟方法,针对含有低速夹层的水平层状介质模型,获得各工况下响应波形数据,并对其进行振幅大小、主频能量及时频分析,从而揭示当低速夹层介质的物理参数改变时,在模型表面一定位置所接收到的响应波形的振幅、频谱及时频的变化规律,验证冲击映像检测方法有效性和精确性。在数值计算的基础上,将冲击映像法应用于天津滨海海河沉管隧道底板注浆效果检测分析,根据现场采集的实测响应波形数据,通过对响应波形可视化处理、频谱分析及时频分析,比较注浆前、后的弹性波特性变化,实现对沉管隧道底板注浆效果的综合评价,获得了良好的检测效果。

It has been a long concerned issue that a variety of measurement techniques is applied to detect the internal structure of underground medium in geotechnical engineering.The theoretical basis of the impact imaging method is to take characteristics of the elastic wave propagating through different medium surfaces.Thus,it has the substantial potential to produce the resolution for target medium and the feasibility for the detection of buried low-velocity layers.In this study,the principle of impacted image detection method was clarified.For the horizontal layered medium model with a low-speed interlayer,a series of response waveform data in each separate case was obtained by using finite difference numerical simulation.Then the corresponding amplitude,dominant frequency energy and time frequency of response waveform were analyzed.Furthermore,their change characteristics were obtained.In addition,the validity and the accuracy of the impacted image detection method were verified.Based on the results of numerical cases,the impact imaging method was applied to detect the grouting quality of the immersed tube tunnel in Haihe Binhai,Tianjin.According to the measurement of waveform data collected on-site,we investigated the visualization of the response waveform,frequency spectrum,time frequency and the comparison of the change characteristics of elastic wave before and after the filling.A comprehensive evaluation was finally realized for the grouting effect on the immersed tunnel baseboard and a satisfied detection result was also achieved.