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August 29th, 2022

Biocalcis® process reinforces weak points in a bridge in Orléans

Soletanche Bachy France has recently completed the Biocalcis® grouting test plot for consolidation of a bridge, as well as the first phase of permanent work, a first for the Group.

Biocalcis, pour renforcer les fondations du pont à Orléans

Biocalcis® used to reinforce a bridge in Orleans

This follows the pilot worksite carried out in Nice in 2015 for an identical application, which won Biocalcis® the Grand Prize in the VINCI Innovation Awards. This is the first time since that date that the process has again been used to strengthen a reinforced soil wall, this time level with the northern abutment of the Pont René Thinat and as a definitive solution.

Many local authorities have been closely monitoring their structures since the collapse of the Pont de Gênes in 2018. This monitoring revealed weaknesses on the Pont René-Thinat, construction of which was completed in 1974.

Depuis l’effondrement du Pont de Gênes en 2018, bon nombre de collectivités surveillent de près leurs ouvrages d’art. Dans le cadre de ce suivi, des fragilités ont été décelées sur le Pont René-Thinat achevé en 1974.

Two areas with specific problems were identified. The first was treated using the Biocalcis® process, while the second has been reinforced by installing 350 metal nails.

With a precise phasing, between the grouting of bacteria and calcifying solutions, the test plot was divided into two areas where two different protocols were used, depending on the position of the boreholes.

The quality of Biocalcis® grouting was assessed by CPT (static penetrometer) and pressuremeter type tests, conducted before and after the works. This test plot enabled optimization of the volumes of calcifying solution to be injected.

First phase of reinforcement work completed

The first phase of final Biocalcis® work (drilling and grouting) began on 30 May and was completed on 14 June 2022. Inspections were carried out the next day, as the reaction is complete within less than 24 hours. Once the bacteria had been injected into the soil, the calcifying solution, which serves as a nutrient to trigger the formation of calcite, was injected half a day after the first stage. The installation of the nails has just been completed.

The teams were able to respect a traffic diversion at the Pont René-Thinat, imposed by the Orléans metropolitan authorities to allow vehicles to flow in both directions throughout the duration of the work.

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