SIMULATION STUDY OF THE EFFECTS OF FROST ON PAVEMENT STRUCTURES AND SUBGRADES

RESULTS ARE GIVEN OF TWO INITIAL SERIES OF TESTS ON PAVEMENTS CONDUCTED TO EVALUATE THE PERFORMANCE OF THE EXPERIMENTAL FROST STATION BUILT IN CAEN, CONDITIONS OF FROST PROPAGATION, AND PAVEMENT SURFACE DISPLACEMENTS CAUSED BY FROST. AN ANALYSIS OF THE MEASUREMENTS TAKEN SHOWS THAT: (1) A LINEAR RELATION EXISTS BETWEEN THE DEPTH OF FROST PENETRATION AND THE SQUARE ROOT OF THE FROST INDEX, THE CRACKS OCURRING AT THE PAVEMENT/SUBGRADE INTERFACE SHOWING THE MARKED DIFFERENCE BETWEEN THE THERMAL PROPERTIES OF THE PAVEMENT AND THOSE OF THE SUBGRADE, (2) FROST PENETRATION IN THE FOUNDATION, OCCURRED AS IF THIS PENETRATION TAKES PLACE ACCORDING TO THE FORMULA ESTABLISHED BY THE CRNS AEROTHERMICS LABORATORY, FROM A FICTITIOUS UNIFORM INITIAL TEMPERATURE IN THE FOUNDATION, (3) THERE EXISTS A LINEAR RELATION BETWEEN THE SQUARE ROOT OF THE FROST INDEX AT THE SURFACE OF THE SUBGRADE AND THE SQUARE ROOT OF THE FROST INDEX AT THE SURFACE OF THE PAVEMENT. THIS MEANS THAT FOR A GIVEN SUBGRADE, THE INFLUENCE OF THE PAVEMENT IS CHARACTERIZED BY TWO PARAMETERS: THE SLOPE OF THE STRAIGHT LINE OBTAINED AND THE VALUE OF THE SQUARE ROOT OF THE FROST INDEX AT THE SURFACE OF THE PAVEMENT WHEN FROST REACHES THE SUBGRADE. THE FIRST PARAMETER DEPENDS ON THE TYPE OF PAVEMENT, E.G. THE MATERIALS USED IN AND THICKNESS OF THE PAVEMENT, THE SECOND PARAMETER DEPENDS ON THE INITIAL DISTRIBUTION OF THE TEMPERATURE AND THERMAL CONDITIONS AT THE PAVEMENT SURFACE. DURING THE SECOND SERIES OF TESTS, WATER ABSORPTION RESULTED IN A MARKED ACCUMULATION OF ICE IN THE FROZEN PART WHICH IN TURN CAUSED FAIRLY IMPORTANT HEAVE OF THE PAVEMENT SURFACE.