# Efficient backcalculation procedure for asphalt pavements using the Finite Element Method

## Palavras-chave:

Backcalculation, Asphalt Pavements, Finite Element Method, Nonlinear Least Squares## Resumo

Backcalculation is a procedure used to estimate stiffness properties (resilient modulus) of asphalt

pavement layers through non-destructive tests. The resilient modulus of each pavement layer is adopted as the one

that produces the simulated deflections closest to the deflections obtained in field tests. This paper presents an

efficient backcalculation approach based on the minimization of the sum of squared errors between the measured

field deflections and deflections obtained using an axisymmetric linear elastic layered model for the pavement

with finite and infinite elements. The resulting nonlinear least squares problem is solved using the Gauss-Newton

(GN) and the Levenberg–Marquardt (LM) methods. The gradients of deflections with respect to the material

parameters used by the optimization methods are computed accurately and efficiently by the finite element code.

The two methods are compared in terms of accuracy, robustness, and computational efficiency for pavement

structures with different characteristics.