GPR signal attenuation vs. depth on damaged flexible road pavements

The findings of a GPR survey carried out on damaged flexible road pavements built on embankments and in cutting sections were reported. The survey was carried out to recognize correlations between: (i) types of damage, (ii) height of embankments or depth of cutting sections, (iii) traffic load and (iv) GPR scan results. Two types of damages, inducing loss of load bearing capacity, were investigated: transversal cracks and ramified cracks. Sixteen sites were chosen, describing the different combinations of the variables to be analyzed. The sites were selected among secondary non-urban roads in the area of L'Aquila (central Italy). Road integrity was evaluated by a GPR quantitative analysis (GPR signal attenuation vs. depth), using an antenna array with a nominal frequency of 1600 MHz. It investigates media till a depth of 1.5 m which is also the maximum depth of influence of the induced traffic stress. The results carried out from two sets of scans (affected and unaffected parts) were compared in order to identify GPR signal changes. These changes made it possible to trace the causes of the damage to the road pavement vs. embankment height, cutting depth and traffic load.