Cavity collapse caused by internal erosion of backfilling sand has occurred frequently at the back sides of coastal structures such as seawalls and quaywalls worldwide. To prevent such geohazards, it is crucial to detect cavities under the pavement at an early stage. This requires an understanding of the processes of cavity formation, development, and collapse, while considering the pavement structure. In this study, based on the above background, prototype-scale experiments were conducted to investigate how different types of backfilling sand and pavement thickness influence these processes beneath asphalt pavement under a water level rise, and how these factors affect the accuracy of ground-penetrating radar (GPR) in detecting a cavity under the pavement. The results revealed the processes and mechanisms relevant to cavity formation, development and collapse beneath the asphalt pavement. Additionally, both the backfilling sand types and the pavement (i.e., asphalt layer) thickness significantly affected the cavity detection depth of the GPR.

internal erosion, cavity, collapse, ground-penetrating radar, asphalt pavement