Roughness of Airfield Pavement on Expansive Clay

The paper presents a brief description of the evaluation criteria for runway profile uneveness (roughness), and discusses four cases histories of roughness analysis of runway pavements on expansive clays in Israel. One case history includes a study of development of roughness over an eight year period and shows that an increase in total heave does not necessarily correspond to an increase in roughness; it is generally the latter which is of major concern from the operational point of view. Existing roughness criteria based on power spectral density analysis were found applicable to runway pavements on swelling clays, although other criteria, based on straight edge analysis were found less applicable when the roughness was mainly due to localized heave. Since overlaying of runway pavements on swelling clays is commonly due to roughness, it is suggested that more effort be devoted to analyzing and predicting roughness development, and its inevitable development should be taken into account in the design procedure.