No-drilling method for the robust frequencies-based analysis of layer thickness backcalculation

Abstract

A frequency-based backcalculation method has been introduced. It makes possible for a pavement backcalculations to be carried out without a known model layer thickness at the input. Presenting results for an asphalt concrete pavement, the authors set out the procedure, which lead to the determination of the total thickness of the pavement asphalt layers based solely on the results of deflection measurements under dynamic load. For field testing, ZiSPON technology equipped with the FWD module was applied. Compared to the methods classically used for determining the thickness of pavement layers, it has been demonstrated that the relative difference between the thicknesses identified by means of the proposed method and the geotechnical drilling or GPR methods lies in the range of 0 to 11%. By using load sequences of 50, 60, 70 kN, the proposed backcalculation procedure may be an element for a fully automated process of assessing the technical condition of the pavement. The procedure is performed automatically, non-invasively (without the participation of a laboratory technician/analyst) and does not require geotechnical drilling. It is assumed that the identified thicknesses can subsequently be used to assess the fatigue life of the pavement structures. A pavement model can be further created with already known total asphalt layers thickness.