METHOD FOR SEPARATELY EVALUATING STRUCTURAL PERFORMANCE OF SUBGRADES AND OVERLYING FLEXIBLE PAVEMENTS

THE STRUCTURAL EVALUATION OFF FLEXIBLE PAVEMENTS IS NOW CARRIED OUT MOSTLY WITH DEFLECTION-MEASURING DEVICES SUCH AS THE DYNAFLECT OR THE BENKELMAN BEAM. THE OBJECT HERE WAS TO DETERMINE WHETHER THE PROPERTIES OF THE DEFLECTED BASIN MEASURED BY THESE DEVICES ON THE PAVEMENT SURFACES COULD MAKE IT POSSIBLE TO EVALUATE THE SUBGRADE AND THE OVERLYING PAVEMENT TOGETHER AND SEPARATELY. IT WAS FOUND THAT, BY MEANS OF THEORETICAL AND FIELD STUDIES, THE MAXIMUM AND OTHER DEFLECTIONS IN THE DEFLECTED BASIN COULD BE USED TO EVALUATE THE STRENGTH OF THE SUBGRADE BEFORE THE PAVEMENT IS LAID OVER IT, THE STRENGTHS OF THE SUBGRADE AND PAVEMENT SEPARATELY AFTER THE PAVEMENT IS LAID, AND THE CHANGE IN STRENGTH OF THE SUBGRADE AND PAVEMENT DUE TO SEASONAL CHANGES OR AGE. A GENERAL CHART WAS DEVELOPED THAT CORRELATES MAXIMUM DEFLECTION AND SPREADABILITY WITH THE SUBGRADE STRENGTH, THE AVERAGE PAVEMENT STRENGTH, AND THE THICKNESS INDEX OF THE PAVEMENT. THIS CHART WAS TESTED FOR SEPARATE STRUCTURAL EVALUATIONS OF THE SUBGRADE AND ITS OVERLYING PAVEMENT FOR PROJECTS IN VIRGINIA. TEN TYPICAL EXAMPLES OF THE PROJECTS ARE GIVEN. /AUTHOR/