New Dynamic Analysis of HWD Results Using Collision Theory

Heavy weight deflectomers (HWD) is a non destructive testing device used worldwide to determine the bearing capacity of airport pavements. An impulse load that simulates an aircraft rolling wheel is applied to the surface of the pavement by means of a falling weight. Geophones, placed on a straight beam, measure the deflection generated under this load. Even if HWD is the international reference device, usual processing methods have shown their limits. They are actually based on static models and adjustment is made on an artificial deflection basin reconstituted from peak values measured on each geophone. This approach is unsatisfactory for two reasons. First, it takes into account only parts of the available information. And secondly, the model is quite far from the observed physical phenomenon. On the contrary, the collision theory being developed by French civil Aviation technical center (STAC) and French central lab for Civil Engineering (LCPC) is a dynamic approach which allows the modelling of the impact of the falling weight on the structure and resulting vibrations. Results from the theoretical model are compared to experimental data by backcalculation.