PAVEMENT ROUGHNESS ON EXPANSIVE CLAYS

The roughness patterns of pavements on expansive-clay subgrades were measured by using the General Mortors profilometer on 20 sections of pavement in Texas. the roughness patterns are analyzed by means of two methods: the Fast Fourier Transform and a technique that reproduces a rod-and-level survey. The analysis shows that the roughness of expansive clays can be viewed as a spectrum of sine wave amplitudes that very dircetly with their corresponding wave lengths. The spectra for each pavement section are fitted by an equation that has two constants: a coefficient and a power. The values of these two constants are found by regression analysis to depend on the flexural stiffness of the pavement, time, climate, and several physicochemical soil properties. An equation that can predict loss of pavement serviceability index was also determined by regression analysis to depend on the same pavement, climate, and soil properties. An example of the use of this equation in the prediction of the performance of a pavement on expansive clay is given, and its implications for pavement design are discussed.

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