Modulus Back-Calculation of Four-Layer System Based on the Characteristic Parameters of Deflection Basin

Falling weight deflectometer (FWD) is the most widely used nondestructive testing method for pavement structure. The back-calculation of structural modulus based on the deflection basin is an important approach to evaluate the service state of pavement structure and study the evolution law of its behavior. Although the deflection of pavement can be approximated as elastic deformation by the instantaneous impact load in FWD testing, the nonlinear response characteristics of structure and materials are non-negligible, which brings difficulties to the modulus back-calculation for a multilayer system. This paper proposes a new back-calculation method of the four-layer structure, which is based on the linear elastic layered mechanical system, through analyzing the empirical relationship between the geometric characteristics of the measured deflection basin and the corresponding moduli of the structural layers. In addition, the feasibility and reliability of this method are evaluated by using the FWD data of the representative structures in the RIOHTrack test road.