水泥混凝土路面脱空振动映象测试技术

脱空是水泥混凝土路面常见病害，是造成路面板断裂的主要原因。当混凝土面板在受到瞬态激振后，其振动频率主要与其脱空与否、脱空程度等因素有关，因此提出了基于振动频率的混凝土路面脱空振动映象检测技术。简述了振动映象测试原理。对混凝土路面板进行了模态分析和模型试验，获得了面板在不种脱空情况下的振动特性。在对路面板振动频率因子分析和路面瞬态振动信号频谱分析的基础上，发现路面板的振动频率对于脱空是很敏感的，从而建立了基于振动频率的混凝土路面脱空判别标准。研究表明：当路面板下严重脱空时，其振动基频值通常小于50 ；当路面板良好支承时，其振动基频值一般在200 以上；当有低于50 与高于200 的两个振动基频同时存在时，表明路面板下存在轻微脱空。

Vibrating image detection technology for cavity beneath cement concrete pavement slab

Cavity beneath slab, which is the chief reason of the cement concrete pavement slab rupture, is the general disease of the concrete pavements. After transient impact by hammer, the vibration frequency of slab relates to the destruction or not, the destruction degree, etc. Therefore, vibration-frequency-based method, namely vibrating image, on cavity beneath concrete slab detection is presented. The fundamental principle of the vibrating image detection is introduced. The modal analysis and model experiment of slab are conducted, and its vibration characteristic in different conditions is obtained. Based on the factor analysis on vibration frequency and the frequency spectrum analysis on transient vibration signal of slabs, the fact that the slab vibration frequency is sensitive to cavity beneath slab is obtained. Thereby, the vibration-frequency-based detection criterion of cavity beneath slab is established. It is concluded that, if the cavity beneath slab is serious, the natural frequency is less than 50 . If the subgrade can support the slab well, the natural frequency is more than 200 generally. The vibration signal of slightly cavity beneath slab is between two conditions above, the natural frequencies both less than 50 and more than 200 exist at the same time.