Ravine La Source bridge

The Guadeloupe Departmental Council initiated the reconstruction of the Ravine La Source bridge on the RD5 at Trois Rivières. This was an ageing structure that no longer met current seismic standards.

The planned structure comprises two traffic lanes with a span of 23 m. The initial plan was to base each abutment with 8 bored piles. However, this solution was not compatible with the site’s access conditions.

Following proposals from Bachy Balineau, the main contractor GTA proposed a more suitable foundation system, in which bearing capacity is provided by a group of 16 micropiles per abutment. These are type III micropiles, with a borehole diameter of 250 mm and a depth of around 12 metres. They are equipped with a main tubular reinforcement (diameter 139.7 mm; thickness 12.5 mm) and an inertia reinforcement at the head (diameter 219.1 mm; thickness 12.5 mm), over a height of 5 m.

To meet the requirements of the Eurocodes, additional micropiles (1 per abutment) were installed prior to the foundations of the structure, and were subjected to loading tests.

It should be noted that the old structure was demolished beforehand and that the drilling platforms, which are relatively cramped, are located almost 5 m below the roadway.

A 200-t telescopic crane was used to access the drilling platforms and carry out all handling operations.