Innovative FWD Testing on Concrete Slabs

Abstract

Falling Weight Deflectometer (FWD) testing is a non-destructive method used to assess the condition of pavement structures. During FWD tests, a weight is let to freely fall upon the top surface of a slab, while a set of geophones located along the driving direction measure the deflections caused by the impact of the falling weight. These deflections serve as input for the back-calculation of subgrade properties. An unprecedented density of deflection data is obtained by means of multi-directional testing [1]. The present contribution refers to two original contributions. The first one refers to the presentation of experimental data from multidirectional FWD testing of one old and one new slab. The second original contribution refers to a structural analysis of the new slab, using a single slab model. In order to best-fit the measured deflections, a spatially uniform modulus of subgrade reaction and a spatially uniform eigendeflection are introduced as optimization variables. This strategy allows for reproducing the measured deflections very accurately, as quantified by a root mean squared error which is as small as 9.6 μm. This underlines that it is indeed possible to introduce a uniform modulus of subgrade reaction in the context of reliably explaining FWD deflection data, even when resorting to a single slab model, provided that a spatially uniform eigendeflection is accounted for.