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| THE VIBRATING IMAGE DETECTION TECHNOLOGY ON CAVITY BENEATH CEMENT CONCRETE PAVEMENT SLAB |
| LIU Hui-xun ,DING Hong-yan |
| School of Civil Engineering, Tianjin University, Tianjin 300072, China |
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Abstract 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.
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Received: 31 March 2008
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2009, Vol. 28 
