Direct estimation of vertical strain at the top of the subgrade soil from interpretation of falling weight deflectometer deflection basins

Abstract

The falling weight deflectometer is a pavement analysis tool that is now widely used in the pavement engineering field. Using the backcalculation process and the measured deflection basin, the layer modulus can be determined and a mechanistic analysis of the pavement can be made. A new approach proposes to bypass the necessity of the backcalculation by allowing a direct estimation of the vertical strain at the top of the subgrade using the deflection basin. A model based on a finite element theoretical pavement analysis is proposed for this purpose. The estimation model revisited existing deflection based index and adapted modifications were proposed to consider thicker pavement structures. The proposed model to estimate the vertical strain at the top of the subgrade is validated and calibrated using data obtained on two instrumented experimental sites.