Abstract: In order to study the applicability of the air-coupled impact echo method for identifying internal defects in tunnel structures, the finite element model of internal defects in tunnel structures such as cavities, cracks and water-containing cavities was established. The response characteristics of the air-coupled impact echo under different defect conditions were analyzed. Tunnel structure models with different defect conditions were poured and experimental research on internal defect detection of tunnel structures based on air coupled impact echo method was conducted. The research results show that the air-coupled impact echo method can well identify internal defects in tunnel structures. The identified defect depths are basically consistent with theoretical values, and the numerical simulation and indoor test results are basically consistent. Whether there is water in the defect has little effect on the impact echo detection results. As the depth of the defect increases and the size of the defect decreases, the identification accuracy gradually decreases. The detection error increases from 0.05% to 3.26% as the defect depths increase from 30 cm to 50 cm, and the defect sizes decrease from 50 cm×50 cm to 10 cm×10 cm.

Key words: tunnel engineering; air-coupled impact echo method; tunnel structure; internal defects; numerical simulation

摘要： 为了研究空气耦合冲击回波法对隧道结构内部缺陷识别的适用性，建立了隧道结构内部缺陷如空腔、裂缝和含水空腔的有限元模型，分析了不同缺陷工况下空气耦合冲击回波的响应特性，浇筑了含不同缺陷工况的隧道结构模型，开展了基于空气耦合冲击回波法的隧道结构内部缺陷检测试验研究。研究结果表明：空气耦合冲击回波法能够很好的识别隧道结构内部缺陷，识别的缺陷深度和理论值基本吻合，数值模拟和室内试验结果基本一致，缺陷内是否含水对冲击回波检测结果影响不大。随着缺陷深度增加和缺陷尺寸的减少，识别精度有所降低，随着缺陷深度从30 cm增加到50 cm，缺陷尺寸从50 cm×50 cm降低到10 cm×10 cm，检测误差从0.05%增大到3.26%。

关键词: 隧道工程；空气耦合冲击回波；隧道结构；内部缺陷；数值模拟