Research on Variation Law of Back-Calculation Modulus of Asphalt Pavement Layer

Based on in-situ FWD testing and laboratory dynamic modulus test, the influence of loading level, position and pavement temperature on FWD back calculated modulus and the relation between bacalculated modulus and dynamic modulus was analysed. The structure combination of asphalt layer was determined based on pavement temperature profile and the composite modulus was calculated based on laboratory modulus test and in-situ measured pavement temperature. The results show that loading level had little influence on bacalculated modulus and testing position had much more influence on bacalculated modulus than loading level. The backalculated modulus and composite modulus decreased with temperature increase, when temperature was low backalculated modulus was greater than composite modulus, when temperature was in room temperature backalculated modulus was equal to composite modulus and when temperature was high backalculated modulus was less than composite modulus. For relation between bacalculation modulus and temperature, temperature correction coefficient for bacalculation modulus was developed and for relation between backcalculation modulus and composite dynamic modulus, correction coefficient model between them was developed.