MECHANISTIC APPROACH TO HIGHWAY REHABILITATION

In this study a mechanistic pavement rehabilitation approach has been developed in which the trends of the common failure types (cracking, rutting and roughness) are evaluated throughout the expected useful life of the overlay. The method is based on obtaining an overlay thickness which provides a serviceability index at the end of the design life of the overlay equal to or higher than a predetermined limiting value. A computer program overlay is developed by modifying the Federal Highway Administration program VESYS in order to select the optimum overlay thickness on deteriorated highway flexible pavements. The program considers the viscoelastic material properties as well as the plastic and fatigue properties of various pavement layers. In this program, strain and deflection responses are computed, then used in conjunction with other criteria to predict pavement distress in terms of fatigue as well as low-temperature cracking, rutting and roughness. The cracking, rutting and slope variance are used to define the pavement performance in terms of the life history of the serviceability index using the AASHTO serviceability equation. The computer program overlay assumes increments of overlay thickness and uses an iteration process in order to satisfy the required serviceability index at the end of the design life of the overlay. For the covering abstract of the seminar see TRIS 450808. (TRRL)