STATEWIDE INVESTIGATION OF FLEXIBLE PAVEMENTS

THIS FINAL REPORT ON THE MARYLAND STATEWIDE INVESTIGATION OF FLEXIBLE PAVEMENTS DESCRIBES THE REVIEW AND EVALUATION OF ALL DEFLECTION DATA OBTAINED IN THE PAST THIRTEEN YEARS. THE DATA COLLECTED FOR EVALUATION INCLUDES THAT COLLECTED ON THE 7 PRIMARY HIGHWAYS OF THE LONG-TERM STUDY AND 142 NEW PROJECTS FIRST TESTED SOON AFTER THEIR COMPLETION. CORRELATIONS WERE MADE BETWEEN DEFLECTION AND THE FOLLOWING VARIABLES: (1) TEST LOCATION, (2) SEASONAL CHANGES, (3) PAVEMENT AGE, (4) PAVED SHOULDER, (5) SUBGRADE SOIL TYPE, (6) PAVEMENT STRUCTURAL VALUE, AND (7) RESURFACING THICKNESS. IN ADDITION, A PAVEMENT PERFORMANCE CRITERION BASED ON DEFLECTION AND CURVATURE WAS PROPOSED AND ANALYZED. SOME CONCLUSIONS MADE ARE AS FOLLOWS: (1) THE INCREASE IN DEFLECTION AT THE OUTER WHEEL PATH RELATIVE TO THE INNER WHEEL PATH IS AFFECTED BY THE SUBGRADE SOIL TYPE, (2) THE DEFLECTION DOES NOT SIGNIFICANTLY INCREASE AS THE PAVEMENT GRADUALLY DETERIORATES OR WHEN A PAVEMENT REACHES THE POINT WHERE IT REQUIRES RESURFACING, (3) THE TYPE OF PAVED SHOULDERS CURRENTLY USED IN MARYLAND DOES NOT AFFECT THE DEFLECTION AT THE OUTER WHEEL PATH RELATIVE TO THE INNER WHEEL PATH, (4) THE DEFLECTION SEEMS TO BE A FUNCTION OF THE STRUCTURAL VALUE OF THE PAVEMENT ON SUBGRADE SOILS OF EQUAL BEARING VALUE, AND (5) THE PERCENT REDUCTION IN DEFLECTION FROM RESURFACING VARIES WITH THE MAGNITUDE OF THE DEFLECTION, SMALLEST AT LOW DEFLECTION AND LARGEST AT HIGH DEFLECTION. A MATHEMATICAL MODEL TO REPRESENT THE DEFLECTION PROFILE IS SELECTED AND PRESENTED. IT IS SHOWN THAT THE RADIUS OF CURVATURE COMPUTED FROM THE MODEL DIVIDED BY THE DEFLECTION MAY BE CONSIDERED AS A CRITERION FOR EVALUATING PAVEMENT STRENGTH AND PERFORMANCE. /AUTHOR/