Numerical Modeling of Thin Pavements Behavior in Accelerated HVS Tests

Two thin road structures have been tested in accelerated testing by using a Heavy Vehicle Simulator (HVS). Both were surface dressed structures, one with a target 20 cm thick unbound base course layer and the other with the base divided into a 10 cm bitumen stabilized base over 10 cm unbound base. The tested road structures were instrumented to estimate deflections, strains and stresses in various locations inside the structure. Numerical analyses, by using two different techniques, the multilayer elastic theory (MLET) and the finite element (FE) have been carried out to simulate the response behaviour of the tested structure and compared with the actual measurements. For both techniques linear and non-linear behaviour of the base was assumed. For the FE method both 2D axisymmetric and a 3D analysis were carried out. The results have further been used to model the permanent deformation development in each layer. The main finding of the study was that induced vertical stresses were generally well predicted in both structures. Better agreement was generally found between the vertical stresses and the actual response with the non-linear response, especially for high loading conditions. The best prediction of surface deflections was obtained in a three dimensional linear elastic analysis where a rectangular loading area was used instead of a circular one in the two dimensional axisymmetric solutions. Generally poor or moderate agreement was found between the strain measurements and the numerical estimations. The simple work. hardening model used to model the accumulated deformation relied on results from repeated load triaxial test results and gave generally good agreement with the results from the testing.