FLEXIBLE-PAVEMENT DESIGN CORRELATED WITH ROAD PERFORMANCE

THE KANSAS METHOD OF FLEXIBLE-PAVEMENT DESIGN IS BASED UPON THE RESULTS OF TRIAXIAL TESTS CONDUCTED ON EACH OF THE COMPONENTS OF THE ROAD STRUCTURE--SUBGRADE, SUBBASE, BASE, AND WEARING COURSE. BY THIS METHOD TESTS ARE CONDUCTED ON UNDISTURBED SOIL SAMPLES CUT FROM THE SUBGRADE AND ON COMPACTED SPECIMENS PREPARED FROM MATERIALS THAT WILL BE USED FOR SURFACE, BASE, AND SUBBASE CONSTRUCTION. THE RESULTING TEST VALUES, WHICH ARE EXPRESSED AS MODULI OF DEFORMATION IN POUNDS PER SQUARE INCH, ARE THEN INSERTED IN A RATIONAL FORMULA AND THE THICKNESS OF PAVEMENT REQUIRED TO SUPPORT EXPECTED TRAFFIC LOADS IS COMPUTED. THIS PROCEDURE PARALLELS THE METHOD USED TO DESIGN OTHER ENGINEERING STRUCTURES. THE STRENGTH VALUE OF EACH OF THE INDIVIDUAL COMPONENTS OF THE ROAD STRUCTURE IS EXPRESSED IN POUNDS PER SQUARE INCH, WHICH IS COMPARABLE TO THE TENSILE AND COMPRESSIVE STRENGTH OF CONCRETE, STEEL, AND WOOD. THE MAJOR FORCES THAT ACT ON THE PAVEMENT ARE THE TRAFFIC WHEEL LOADS, WHICH MAY BE PREDICTED WITH REASONABLE ACCURACY AND ARE SYNONYMOUS WITH THE AXLE LOADS ACTING ON A BRIDGE OR THE FLOOR LOAD WITHIN A BUILDING. THE FORMULA TO WHICH THE TRIAXIAL-TEST DATA IS APPLIED IS THE ONE DEVELOPED BY PALMER AND BARBER, WITH THE ADDITION OF THE TRAFFIC COEFFICIENT BASED ON THE EXPECTED VOLUME OF TRAFFIC, AND THE SATURATION COEFFICIENT, BASED ON THE AMOUNT OF ANNUAL RAINFALL IN THE VICINITY OF THE PROJECT UNDER CONSIDERATION. RESULTS OBTAINED BY THIS METHOD ARE CORRELATED WITH ROAD PERFORMANCE. /AUTHOR/