Influence of drainage on flexible road pavement design

Road pavement serviceability is primarily governed by the type of vehicles anticipated to use the facility. Along with the size of traffic loads, climatic conditions affect the behavior of the materials in a pavement structure. The relative strength loss in a layer due to its drainage characteristics and the total time it is exposed to near-saturation moisture conditions is represented by drainage coefficients. There is a need for computerized methodologies for thickness design of flexible asphalt pavements (granular base course) for a wide variety of pavement uses providing users the capability to conduct structural analysis of special pavement structures. An algorithm for a computer-based procedure towards the calculation of the layer thickness of flexible pavements has been developed. The design equation used is that described by the American Association of State Highway and Transportation Officials. The present work deals with the effect of drainage on the total thickness of the structure as it directly influences the cost of large infrastructure projects like roads. The output of different cases solved is presented in table and schematic form. Changes in technology related to pavement design and construction practices will necessitate revisions to currently used computing techniques. Improvements in computing times which will affect the cost of computerized methods available to engineers are to be suggested in the near future. Empirically supported pavement designs used nowadays in Greece require modifications based on regional experience and on a better assessment of the drainage conditions prevailing in each area crossed by a roadway project. Since design considerations constantly change, it is obligatory to shift towards more sophisticated design methods.