Monitoring of the rock mass deformation under the Pont du Gard pier VII foundation

The Pont du Gard is a Roman aqueduct bridge built around 50 AD to ensure the crossing of the Gardon river by an aqueduct supplying the city of Nîmes (France). Located between piles VII and VIII, the minor bed of the Gardon forms a deep channel whose possible instability of its flanks has long attracted attention. Two instrumented rock bolts were sealed in the rock foundation of the pier VII and were monitored for several years. This auscultation reveals some deformations of the rock under the effect of atmospheric temperature. But small events seem to be assigned to the variation of the water temperature during Gardon floods. The site, the instrumental set-up and the main results of the auscultation are described in this paper.