A Case Study on Detection of Subsurface Cavities of Urban Roads Using Ground-coupled GPR

The city of Seoul has been in trouble due to road safety problems induced by a sudden and random road cave-ins. Extensive field investigations have been conducted to understand the phenomenon of the road cave-ins. This study introduced the results of field investigation on the development of road cave-ins and subsurface cavities. Ground penetrating radar (GPR) test results also reported to detect subsurface cavities which may become road cave-ins in the future. Field tests indicate that most subsurface cavities consist of three parts: head, body, and tail. The causes of the cavities were sewage defects, lack of backfill compaction, and insufficient earthwork. Subsurface cavities were detected successfully using the GPR tests and repaired according to the level of road cave-in potential. Two years of GPR tests and restoration resulted in a 67% reduction in the urban road.