Experimental and theoretical investigation of three dimensional strain occurring near the surface in asphalt concrete layers

Several pavement failures have been observed to be initiated at or near the surface of the hot-mix asphalt layers and some of them propagate downward through the surface layer (top-down cracking). These modes of failure are affected by heavy vehicular loading configuration, pavement structure and their interaction at the tire-pavement contact. This paper documents an experimental investigation of surface strain induced under the entire tire by using specific instruments based on fiber optic sensors. Two innovative retrofit techniques which allow measuring strains in the upper parts of the asphalt layer have been used on the IFSTTAR’s test track facility. The association of these two techniques allows obtaining the strains, few centimeters below the surface, in three directions: longitudinal, transverse and vertical. Two pavement structures with two temperatures (moderate and hot) have been tested. Shape of the signal under the tire and magnitude of strain are compared with viscoelastic model pavement calculations.