为研究空洞缺陷尺寸以及监测点和震源点的位置对检测结果的影响，根据冲击回波法的特点，设计并进行一系列空洞直径不同时混凝土板的检测试验，模拟检测公路隧道衬砌的壁后空洞。采用快速傅里叶变换分析振动加速度信号，研究应力波的频域信号特征，以探索冲击回波法探测衬砌空洞的可能性与机制。试验结果表明,冲击回波法在探测衬砌空洞缺陷中显示出较为良好的检测效果，影响检测效果的因素主要包括空洞缺陷直径、测点布置和激振位置等。

The influence of void size, the location of monitoring points and vibration source points on the detection results is very important. Hence, a series of detection tests on concrete decks with defects of various diameters are designed and carried out to simulate and dectete the void condition behind tunnel lining based on the characteristics of impactecho method. In order to explore the possibility and mechanism of detecting lining void by impactecho method, the fast Flourier transform (FFT) method is employed to analyze the vibration acceleration signal; and the characteristics of frequency domain signal from stress wave are studied. The experimental results show that the impactecho method performs well in detection of lining void condition; and the main factors affecting the detection effect include void diameter, arrangement of monitoring points and location of seismic source.