FACTORS INFLUENCING THE RESILIENT DEFORMATIONS OF UNTREATED AGGREGATE BASE IN TWO-LAYER PAVEMENTS SUBJECTED TO REPEATED LOADING

INTEREST IN PAVEMENT DEFLECTIONS UNDER MOVING WHEEL LOADS AS A MEASURE OF PAVEMENT PERFORMANCE AND THE NEED FOR A PROCEDURE WHEREBY THESE DEFLECTIONS MIGHT BE PREDICTED IN ADVANCE FROM SUITABLE LABORATORY TESTS, GENERATED THIS INVESTIGATION. THE INVESTIGATION ENCOMPASSED THE MEASUREMENT OF RESILIENT BEHAVIOR OF FOUR UNTREATED GRANULAR MATERIALS IN TRIAXIAL COMPRESSION REPEATED LOAD TESTS IN THE LABORA- TORY, MEASUREMENT OF DEFLECTIONS IN FIELD PROTOTYPE PAVEMENTS COMPOSED OF ONE OF THESE MATERIALS (A WELL-GRADED, PARTIALLY CRUSHED GRAVEL) AND A COMPRESSIBLE FINE-GRAINED SUBGRADE SOIL USING REPEATED LOAD PLATE TESTS, AND THE RELATING OF THE LABORATORY TESTS TO THE OBSERVED DEFLECTIONS OF THE PROTOTYPE PAVEMENTS USING ELASTIC THEORY. RESULTS OF REPEATED LOAD TRIAXIAL COMPRESSION TESTS ON THE GRANULAR MATERIALS INDICATE A UNIQUE RELATIONSHIP BETWEEN THE MODULUS OF RESILIENT DEFORMATION (ANALOGOUS TO AN ELASTIC MODULUS) AND CONFINING PRESSURE. THE MODULUS CAN VARY CONSIDERABLY OVER THE RANGE IN STRESSES USUALLY ENCOUNTERED IN PAVEMENTS. RESULTS OF REPEATED LOAD PLATE TESTS INDICATE THAT THE RESILIENT DEFORMATION OF AN UNTREATED BASE COURSE DEPENDS ON /1/ CONFINING PRESSURE-THE AVERAGE MODULUS OF RESILIENT DEFORMATION INCREASED WITH THE CONFINING PRESSURE, /2/ THICKNESS OF BASE-THE RESILIENT DEFORMATION OF THE BASE INCREASED AS THE THICKNESS OF THE BASE WAS INCREASED FROM 8 TO 12 IN., AND /3/ PLATE DIAMETER-WHEN THE SURFACE PRESSURE REMAINED CONSTANT, RESILIENT DEFORMATION OF THE BASE COURSE DECREASED AS THE DIAMETER OF THE PLATE WAS INCREASED; I.E., THE RESILIENT DEFORMATION PER INCH THICKNESS OF BASE DECREASED AS THE RATIO OF PLATE DIAMETER TO BASE THICKNESS INCREASED. RESILIENT DEFORMATIONS COMPUTED FOR THE PROTOTYPE PAVEMENTS USING THE RESULTS OF THE LABORATORY TESTS TOGETHER WITH A MODIFICATION TO THE BOUSSINESQ THEORY TO ACCOUNT FOR THE VARIABILITY IN DEFORMATION CHARACTERISTICS OF THE GRANULAR MATERIAL WERE IN REASONABLY GOOD AGREEMENT WITH THE MEASURED DEFORMATIONS. THUS IT WOULD APPEAR THAT RESULTS OF REPEATED-LOAD TESTS ON PAVING MATERIALS CAN BE USED WITHIN THE FRAMEWORK OF AVAILABLE THEORY TO PREDICT TRANSIENT PAVEMENT DEFLECTION.

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