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Tunnel units begin their journey to the bottom of the Tyne
View the latest ‘Activity Diary’ detailing works for the New Tyne Crossing.
View the ‘360 dry dock’ image.
View the Dry Dock from the North and the South.
The second vehicle tunnel is being built using immersed tube technology in the river section. This has involved dredging a deep trench in the bed of the Tyne for the immersion of pre-fabricated concrete sections.
The river section of the new vehicle tunnel will connect to the cut-and-cover sections of the tunnel, either side of the River Tyne, via dedicated transition structures on each river bank.
Each transition structure consists of a shaft which is constructed with three diaphragm wall panels (underground reinforced walls) and one steel ‘combi’ pile wall on the river side of the structure. The bottom of the shaft has an inbuilt concrete slab which acts as a support for the walls of the structure. The combi pile wall will be removed to enable connection with the river tunnel sections.
The course of the new tunnel across the River Tyne has been dredged using techniques to minimise potential impacts on river ecology, and shipping.
The river section of the tunnel comprises four concrete pre-cast tunnel elements, which will be constructed at Walker dry dock, approximately 3km upstream of the tunnel site. Each tunnel element is approximately 90m long, 15m wide and 8.5m high. The elements have been built within dry dock number 4, on a free draining material, and each will be made up of four separate segments to enable a more robust final product to be built. Ballast tanks have been placed within each tunnel element to enable final transportation.
The dry dock will be flooded and the tunnel elements will be floated out to the river, and downstream towards the tunnel site. Before being lowered into place the tunnel elements will be berthed at Howdon Dock so that they can be fitted with immersion equipment.
Each element will be lowered into place, sequentially, once it is ready for immersion. Each element will be towed into the river channel and once secured in position the internal ballast tank will be filled to enable the element to sink. Using cables the element will be carefully lowered into place on the dredged river bed. Once in place the tunnel elements closest to the river banks will be pulled towards the transition structures so that the connection between the two can be made.
Sand will be injected below each tunnel element, to secure it in place, using a sand flow technique. Once all tunnel elements are in place a closure joint will be constructed in situ to seal the elements together. Rock armouring will be placed above the tunnel, along its entire length, to protect the tunnel structure.