Identification of Cavities Underneath Concrete Pavement Based on Pavement Vibration

Cavities beneath concrete pavement slabs, usually resulting from erosion or foundation settlement, increase the flexural-tensile stress in the slabs, which may cause distresses, such as joint faults and fracture. To avoid such distresses, this study proposes a vibration-based method for the identification of cavities underneath concrete pavements. Through finite element analysis, it was found that the cavities significantly affected the local vibration characteristics in terms of the frequency spectrum; however, they had negligible effects at other positions. Additionally, the location and extent of the cavities affected the local frequency spectrum. On this basis, a distributed optical vibration sensing-system (DOVS) was developed and utilized to measure the vibration characteristics of the concrete pavement. Furthermore, a laboratory test was conducted to study the influence of the extent of cavities, and the frequency spectrum was obtained using time-frequency analysis. The correlation between the frequency spectrum and the extent of cavities was studied, and it was observed that the spectrum of 20-150 Hz was sensitive to the extent of cavities, and hence, an index expressed as "weighted frequency" was used to identify the cavities. During the field tests, the DOVS was established in three concrete pavement slabs at Longhua Airport, Shanghai. This vibration-based cavity identification method was compared with other conventional deflection-based methods, and a good coherence was observed between the identification results of these two methods, indicating that the vibration-based method is reliable for cavity identification. © 2020, Editorial Department of China Journal of Highway and Transport. All right reserved.