Management of cavities under flexible pavement road network in metropolitan area: Detection, evaluation, and rehabilitation

Abstract

This study evaluated a management program of cavities under flexible pavement road network in Seoul Metropolitan City. Consequently, directions for improvement were suggested. The underground cavities beneath the pavement layer were scanned using a vehicle-type multichannel ground penetrating radar (GPR). In addition, the size information including overburden thickness, cavity height, and lengths in longitudinal and transverse directions of the cavities were estimated and compared with the volume of cavities measured via a digital cavity imaging (DCI) system. Moreover, the change in the cavity dimensions with time was monitored. Through field investigation, the cavity volume near the asphalt pavement surface was observed to be smaller than the cavity located in the deep. For certain locations where the cavity existed, pavement cracks on the asphalt surface were identified. Thus, the crack width and depth were measured for the selected 14 locations and compared with the dimensions of the cavities. The results demonstrated that the depth of crack rather than the width exhibited a meaningful correlation with the cavity size. Additionally, the cavities under the flexible pavement layer were repaired using a low-strength filling repair material. Further, the elastic modulus on the pavement surface above a cavity was assessed using a light weight deflectometer (LWD) before and after the rehabilitation process and compared with the value of elastic modulus on the normal surface with no cavity but near the repair work. The results demonstrated that although the rehabilitation process increased the elastic modulus of the pavement layer, it could not be fully recovered owing to the characteristics of the repair material. Furthermore, the rehabilitation process was found to be more effective as the size of cavity was small.