Bridges over railways
The western end of the Hazebrouck bypass needed to cross two very busy railway lines (Arras-Dunkirk and Lille-Calais). The electrified lines and the constant flow of trains presented substantial safety hazards which had to be considered in the design of the two bridges. The optimum solution was found to be two single span bridges supported by sheet pile abutments.
Approximately 300 tonnes of U profile sheet piles were installed using hydraulic jacking techniques. This method minimised vibrations which enable sensitive SNCF electronic equipment (only one metre from the piled walls) to function during the construction process, and also limited possible safety hazards to personnel working in the vicinity of the tracks.
Not only was this solution chosen on the grounds of safety, it was also found to be the most economic method of construction.
Two abutments were completed within two weeks and rail traffic was virtually uninterrupted; in fact the first wall of 54 sheet piles was jacked to an average depth of 8 metres in 5 working days, which included some temporary works.
The scheme was successfully completed on schedule and within budget, and complied with all quality and environmental requirements.
|Client||Ministère de l''Equipement, du Logement et du Tourisme|
|Prime Contractor||Direction Départementale de l''Equipement du Nord District of Dunkirk|
|SNCF||District of Hazebrouck|
|Sheet piles||PU20, 141 kg/m2, 2 000 cm3/m|
|Other profiles used||PU25: 67 t, PU8/PU6 : 12 t.|
|Steel grade||E 240|