Nondestructive methods complemented by FEM calculations in diagnostics of cracks in bridge approach pavement

Nondestructive methods of road pavement diagnostics are an alternative to traditional approach to pavement failure investigation. The article presents a detailed multidisciplinary inspection carried out using ground-penetrating radar (GPR), laser scanning technology and finite element method (FEM) calculations. It was done in order to assess the factors that contributed to occurrence of premature cracks of a bridge approach pavement. Assessments of permittivity values in the GPR method are dependent on two factors: thickness of successive layers and electromagnetic wave reflection in time. Electromagnetic field propagation in the pavement structure was also simulated using two numerical models: the first one reflected the undamaged pavement, while the second one included the defects next to the bridge joint. The comparison of the radargrams for both models enables identification of reflections and anomalies caused by the assumed defects. Nonhomogeneous compaction zones in the bridge approach pavement structure were detected by analysis of layer permittivity and anomalies observed in the in situ GPR maps. The GPR measurements were positively verified afterwards by values of air void content in the pavement layers, determined in standard invasive tests. Laser scanning technology was also used in the distressed area in order to assess its geometric changes. Results are presented in the form of contour plots depicting differences between the measured and the designed surfaces. The three-dimensional finite element (FE) model of the approach pavement was created to determine pavement deformation under moving load and stress state next to the bridge joint. The influence of insufficient support of the top asphalt layers on pavement response was investigated. The analysis of the cracks shows that some errors were made both during the design process and construction of the bridge approach pavement. •The proposed methodology reduces the number of wells drilled on roads.•The use of nondestructive methods for pavement diagnostics or assessing premature damage to the surface around engineering structures is important.•Nondestructive methods are an alternative to invasive tests in determining the factors which cause cracks on a bridge approach pavement.•Research results confirmation based on the mathematical model used in FEM calculations.