Deflection Measurement: The Need of a Continuous and Full View Approach

Road pavement bearing capacity is a crucial point for road maintenance and rehabilitation. Maximum deflection is usually measured discontinuously by mechanical sensors at low speed which implies safety problems. Pavement simulations showed that some parameters describing the deflection basin are more sensitive to pavement damages (cracking or delamination) than the maximum deflection. A direct measurement of surface deflection could be very useful to estimate such parameters. A new measurement system based on an imaging technology is presented. It consists in the projection of a structured pattern on the road surface A camera analyses the pattern deformation, which allows for measuring a surface deflection. The technique has been laboratory qualified in order to measure shapes, displacements and slopes on a road. A first experiment was carried out with a static system on the LCPC test track. The imaging technique was able to measure a surface deflection with satisfactory metrological performance.