ABSTRACT
Several non destructive road structure evaluation methods have been developed over the last fifty years. This chapter describes key non destructive techniques used for road evaluation plus several interpretation methods. In deflection-based methods, a load is applied on the surface of the road vertical displacement at the loading point is measured. Transient methods use transient impulses to approximate the load produced by a truck moving at a certain velocity. The Pulse Velocity method measures the travel time of compressive and shear waves by placing a set of ultrasonic transmitters and receivers at a known distance and estimating the wave velocities using a simple relationship between distances and times. Wave numbers are obtained using the Finite Element Method, and finally, information in the time domain is obtained again using an inverse Fourier Transform. The Spectral Element Method, which combines the Finite Element Method with spectral analysis, is used for dynamic analysis in the frequency domain.
