Removal of a level crossing, Agde, FR | 2023

Improving safety and traffic flow: Replacing level crossing PN 288 in Agde

Level crossing PN 288 is located immediately outside Agde railway station, at the intersection with Route Départementale 13 and on the banks of the Canal du Midi. Crossed by around 150 trains and almost 10,000 vehicles a day during the summer months, it was classified as a 1st category crossing by prefectoral decree in 1993. As a result of these characteristics and the accidents that have occurred at this level crossing, it has been included in the "national safety programme" by the French government and SNCF-Réseau. 

Because of the heavy rail traffic and the frequent closure of the level crossing, the avenue is regularly congested with long queues of cars, leading to a deterioration in the living environment of local residents and an increased risk of accidents. Air pollution and noise nuisance are also aggravated. Urban development and the use of existing transport infrastructure are set to accelerate in the area, particularly at the level of the level crossing. In this context, the increase in road traffic is likely to make traffic conditions even more difficult.

Removing PN 288 and replacing it with a rail bridge over the RD13, as well as the associated roadworks, will help to improve the daily lives of local residents and transport users, whether by rail or road.

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To carry out these works alongside the Canal du Midi, SNCF Réseau, the structure's designer, opted to builda watertight enclosure using AZ®-700 Sheet pile wall and a combination of tubes and AZ® Sheet pile wall under the railway bridge to ensure its load-bearing capacity during the temporary phase. 

The solution implemented complies with the call for tenders, apart from the access hoppers, for which NGE Fondations, on the strength of its positive experience on the reinforcement of the St Laurent du Var dykes, proposed the latest generation of AZ®-800 Sheet piles. The AZ 18-800, AZ 22-800 and AZ 27-800 sheet piles have advantageously replaced the AZ 14-770 and AZ 28-700 initially selected by SNCF réseau, confirming their perfect suitability for the ground conditions of the project. In this way, NGE Fondations has been able to achieve a high level of installation performance with standard driving equipment and a reduction in sheet pile mass. This variant makes it possible to optimise the project's resource consumption and reduce its carbon footprint, while cutting costs and improving productivity.

In the provisional phase, i.e. during the construction of the road opening and the final supports, the rail bridge is supported by 28 m long, 14 mm thick, Ø 1219 mm Tube Piles, anchored in the deep sandy gravel. 

Driving this part of the watertight enclosure in a combination of tubes and sheet piles in the railway right-of-way was carried out under Temporary Interruption of Rail Traffic (ITC) for a period of 120 hours. 

PN 288 at Agde takes the implementation constraints up a notch. Here, 2 mixed curtains of tubes and planks were driven simultaneously under ITC, with the tubes first driven by vibration and ramming, which also included checking the bearing capacity of the tubes. This was followed by driving the AZ 13-770 intermediate sheet piles between the steel tubes.

The time allowed for driving the mixed curtain within an ITC of 120 hours, including checking the bearing capacity of the tubes, was made possible by adapting the usual driving equipment to the constraints of mixed curtains. In addition to a double driving workshop, NGE Fondations has reinforced its sheet pile driving guide system by integrating mobile ‘derricks’ to guide the tubes (see driving guide in illustration). 

Work is currently under way, with commissioning of the structure scheduled for June 2023.