Two milestones for Tyne

Two milestones were reached on the Tyne Tunnel river crossing in Newcastle, UK. On December 22nd, design and build contractor, Bouygues Travaux Publics, broke through the concrete wall at the end of the first section of sprayed concrete lined (SCL) tunnel in Jarrow, whilst earlier in the month the cutter suction dredger ‘Vesalius’ concluded its dredging operation on schedule.

The new vehicle tunnel comprises two short sections of SCL of 32m and 40m which equates to approximately 4% of the land tunnel excavations. It was decided to apply SCL techniques to these two locations in Jarrow in order to avoid major utility diversions. Cut and cover methods are being applied to the rest of the land side tunnelling.

Nicolas Caille, project managing director for Bouygues Travaux Publics, said: “This is a very challenging and technically specialised part of the project. I’m delighted with the progress we’re making here. By using this approach we have been able to avoid the disruption of serious utility diversions, including a major gas main that runs across the site.”

All necessary cut and cover excavations were completed in October 2009, and floor and roof slabs are currently being built at the bottom of the trench. The tunnel breakthrough marks the uniting of the first section of completed SCL tunnel with the rest of the excavation. Previously, it had been separated by a temporary underground concrete wall.

The trench to accommodate the installation of the four pre-cast concrete tunnel sections that will make up the new vehicle tunnel has now been fully completed. Despite adverse weather conditions including several heavy rainstorms during the five week dredging period, the operation finished on schedule. The impact of the dredge was carefully monitored throughout the operation using the live information transmitted from five dedicated water quality monitoring buoys.

The cutter suction dredger ‘Vesalius’ has now been demobilised following completion of the works and has been transported away from its site at Howdon Basin.

Four 90m long tunnel sections have been built at Walker Dry Dock. The dry dock was flooded at the beginning of December to enable the units to be floated out of the dock early in the New Year ready to be placed in the trench.