Deformation Modelling of Instrumented Flexible Pavement Structure

A flexible test road structure was built and tested in an Accelerated Pavement Test (APT) using a Heavy Vehicle Simulator (HVS) to monitor its performance behaviour. In the tests more than one million load cycles were applied, but mid-way the water table was raised, allowing the structure to be analysed in "moist" and "wet" state. The raised water level had a significant effect, decreasing the resilient modulus and increasing the rate of accumulation of permanent deformation (PD). The structure was instrumented to measure stress, strain and deflection responses as a function of load repetitions as well as PD manifested on the surface as rutting. The structure has been modelled in an axisymmetric analysis using a 2D multi layer elastic theory (MLET) as well as a 3D finite element method (FEM). The methods generally both agreed well with the measurements. The observed accumulation of PD of the unbound layers was modelled using three different material models, both stress and strain based with responses gained from both MLET and FEM. The modelled deformation, is compared to the measured deformation in both "moist" and "wet" state, with some difference observed between models and methods but generally reasonably agreement was established.