Jarrow

View the latest ‘Activity Diary’ detailing works for the New Tyne Crossing.

Whereas the majority of this section has involved cut-and-cover techniques similar to that undertaken in the North Approach, two short sections of the tunnel will be constructed via traditional underground boring techniques.

The cut-and-cover section of the tunnel involves both diaphragm wall methods and secant piling. The majority of the tunnel section is made up of diaphragm walls, constructed either side of the tunnel route.

Once these diaphragm walls were built, the space between them was excavated and the tunnel constructed in situ. For the section of tunnel using secant piling, the technique is similar to that of the diaphragm wall sections. Interlocking piles are used to create the supported space for excavation rather than reinforced underground walls.

Where the tunnel is bored, a technique called "Sprayed Concrete Lining" is being used. This involves boring out the material from below ground and spraying the space with concrete as the excavation proceeds, in order to support the excavated space. This is a safe and well-established technique enabling utilities and certain roads to remain undisturbed by construction activity. The sprayed concrete lining sections comprise an outer sprayed concrete primary lining and an inner cast in situ permanent lining.

In addition, an in situ reinforced concrete box structure is being constructed, which will form the final southern end of the tunnel, and will extend out to the south junction, from underneath the newly constructed Howard Street road bridge (see 'South Approach' for more information).

The South cut-and-cover section runs from the southern tunnel portal in Jarrow to the riverside transition structure on the southern bank of the Tyne, a distance of approximately 840m.