The Belgian railway operator, Infrabel, urgently needed to repair defective concrete in the Biéreau tunnel just south of Brussels. Hydrodemolition with a Conjet Robot 365 was used to selectively remove the damaged and decaying concrete at record speed.
The 875-m long, 10.5-m diameter Biéreau tunnel forms part of the 4.4-km long dual Line 161D railway track linking the cities of Ottignies and Louvain-la-Neuve, 34 km south of the Belgian capital Brussels. It was opened in 1975 and during its near 40 years of service, the tunnel’s concrete skin had deteriorated and parts were falling off. It needed urgent repairs and Belgian railway operator, Infrabel, has invested more than €4 million ($4.25 million US) in the tunnel’s restoration.
Closing the tunnel completely was not possible due to public transport demands in the urban area. So it was decided the only option was to restore the tunnel in two sections and working and repairing the concrete from one track while trains passed by slowly on the other line. The restricted space and necessary safety and environment precautions were critical considerations for the overall renovation project, which had to be completed in just 220 days.
Due to these restrictions, the restoration contractor Bageci, a regional branch of industrial Belgian Group CFE, opted for the hydrodemolition technique, which uses a very high-pressure water jet to selectively remove the defective concrete from the walls and roof. Bageci bought a Conjet Robot 365 with multipurpose arm and a specially adapted feedbeam, carrying the cradle and jetting lance, to fit the curvature of the tunnel wall. Conjet’s representative in Belgium, BPC International, sold the hydrodemolition equipment. The company was also responsible for service, support and spare parts supply to guarantee 24-hour productivity and availability of the Conjet robot.
A 500-kW Hammelmann S1200-48 high-pressure water pump and the Conjet Robot were installed on flatbed rail wagons fitted with foldable, protective walls. This allowed the hydrodemolition and restoration work to be completed on one side of the tunnel while trains could safely pass on the opposite track.
“Due to the special safety and environmental demands and lack of space, hydrodemolition was really our only option from the very start,” said Bageci tunnel project manager Luc Bosmans. “We thought it was going to be the most productive method for this tunnel work, and it proved to be very efficient.”