Degradation of Road Pavements Built in Cutting Sections Evaluated with Gpr

Structural degradation of road pavements has a considerable impact on traffic safety. Roadway surface defects or discontinuities make driving uncomfortable and increase chances of accidents. GPR is an effective and non-destructive technique to discover and trace the causes of road pavement damages so characterizing road integrity. The paper shows the findings of a GPR survey carried out on degraded road pavements built in cutting sections. The survey was expected to find correlations between: (i) types of damage, (ii) depth of cutting sections, (iii) traffic load and (iv) GPR scan results. Five types of damages, inducing loss of load bearing capacity, were investigated: (i) transversal and longitudinal cracks, (ii) only longitudinal cracks, (iii) only transversal cracks, (iv) ramified cracks and (v) failures. To determine the impact of cutting depth and traffic load on road pavement degradation, the survey focused on high (depth > 4 m) and low (depth < 2 m) cuttings, as well as on heavy traffic (average daily traffic > 4000) and low traffic (average daily traffic < 1000) road pavements. Twenty sites were chosen in the area of L’Aquila (central Italy), describing the different combinations of the variables to be analysed. Road integrity was evaluated by a GPR quantitatively analysis (GPR signal attenuation vs. depth), using a 1600 MHz antenna. It investigates media till a depth of 1.5 m which is also the maximum depth of influence of the induced traffic stress. GPR scans were first made on the degraded part of the road and then extended to its nearby unaffected part. The results carried out from the 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. cutting depth and traffic load.