Instrumentation of an Innovative Pavement Section on Motorway A10

Recently, the French motorway company Cofiroute has decided to reconstruct the slow lane of a section of the motorway A10, located west of Paris. This section supports a very heavy traffic, of about 4000 trucks/day (corresponding to 4800 french standard equivalent 130 kN axle loads). The solution adopted for the reconstruction consists in retreating in situ, with a hydraulic binder, the existing bituminous subbase, and adding new base and surface layers, incorporating 30 % of recycled materials from the old pavement. To validate this novel solution, and in particular the in situ retreatment, Cofiroute asked IFSTTAR (the French Institute of Science and Technology for Transport, Development and Networks) to instrument this pavement structure. Four sections were instrumented with classical strain gage sensors, placed at different levels in the pavement (subgrade, treated subbase, bituminous base), and temperature sensors. On a fifth section, a more innovative instrumentation, including geophones, crack opening sensors, and temperature sensors was installed, associated with a remote data acquisition system. The instrumentation was installed during construction, in November 2011, and most transducers are still functioning. The paper presents the monitoring of these experimental sections. The strain gage measurements were used to fit a mechanical model of the pavement structure, and to evaluate the modulus of the different pavement layers, and their evolution with time. The results confirmed the good performance of the in situ retreated subbase, and validated the technical choice of the road owner. The geophones are very sensitive sensors, which measure vertical displacement velocity. Different methods of treatment of the geophone measurements were proposed, to monitor pavement deflections, and also to identify and classify truck silhouettes, and estimate truck loads.