Evaluation Of Road Roughness Based On Multi-fracial Theory

With the swift and violent development of road career, the requirement ofride comfort is enhanced continually. And in the field of road engineering, roadroughness is one of the evaluation indexes of the pavement service quality. So itis very significant for the quality of road services to analyze on the road surfaceroughness, reasonably carry on appraising and grading the roughness.However, the most commonly used road roughness index in China’shighway industry, such as the Mean-Square Deviation(σ), the InternationalRoughness Index(IRI), the Power Spectral Density(PSD), the Root Mean-SquareVertical Acceleration(RMSVA) and so on, are statistical and general summariesfor the digital features of road longitudinal profile, which do not show thedifferences in the partial information of roads with the same evaluation index,though, to some extent, the condition of the road can be reflected.This paper studied on multi-fractal according to the shortages of the currentused road roughness indices. So multi-fractal theory was used to systematicallyresearch into appraising the road profile based on multi-fractal can fine depictingthe characteristics of the road locally.In this thesis, positive analyses on series of road profile are carried out. Andthe results show that road profile have the obvious multi-fractal characteristics.On this basis, multi-fractal spectrum and the parameters can be used in theresearch of the road profile. Then we found that only multi-fractal spectral widthcannot determine the road roughness condition. Through the simulation of roadsurface in each grades based on Fourier inverse transformation, result showedthat there was no unique relation between multi-fractal spectral width and roadroughness in different grades, but the vertical，intercept of the roads thathave the same multi-fractal spectral width was different in Logarithmicdistribution of measure and scale.Finally we proposed to signify the road roughness by regarding thecombination between multi-fractal spectral width and the IRI. So it can be usedas supplement of current indices when necessary.