Environmental Issues
Moving the earth
Tyne crossing benefits from Sirius expertise
The Sirius Group has employed a range of engineering services
to help with one of Britain’s biggest transport infrastructure
projects: construction of the new Tyne Crossing, the second
vehicle tunnel under Newcastle’s River Tyne.
Sirius was directly employed by Bouygues Travaux Publics (UK
Branch), part of the TT2 consortium which is part-financing,
designing and building the £260 million project.
The Sirius work originally entailed enabling earthworks along
the line of proposed diaphragm walls/haul roads which covered
an area of approximately 20,000m
2
. Sirius was then tasked with
defining the extent of gas works contamination present within
riverbed sediments on the line of the new tunnel. The contract
has now been expanded to include the main excavation of the
south cut-and-cover section of the tunnel, which represents the
largest and most technically demanding engineered earthworks
package available on the project. Over 200,000m
3
of soil was
removed, with 394 support props and 15 steel shaft frames
The Tyne, with Sirius work taking place on the southern bank
installed in 24 weeks. Sirius also successfully avoided the need
for landfilling by securing an environmental permit and planning preparation for the bentonite batching plant. Then, to enable
permission for temporary storage of all surplus soils. geotechnical specialist contractor Bachy Soletanche to excavate
the diaphragm walls, it was necessary for Sirius to improve the
From soil testing to soil excavation ground by cement stabilisation in order to prepare an appropriate
In determining the extent of contamination, Sirius outperformed platform for their cranes and heavy excavating equipment.
expectations, reducing the scheduled over-water drilling works
to obtain samples for chemical analysis from two weeks to four Cut-and-cover excavation
days, the client benefiting from a significant cost saving as well Works to create the new tunnel, on the southern bank of the
as a job well done. The excavation work has been a more River Tyne, extend over a distance of around 1 km in length,
challenging project: first, Sirius prepared the south platform, reaching depths of up to 30 metres in places.
including large-scale excavation and re-profiling of soils in In order to gain a complete understanding of the main cut-and-
cover excavation works, Sirius prepared a scale-model of the
new tunnel for the south section of the site, demonstrating how
equipment could access between a tight network of tailor-made
props, which are being used to brace the diaphragm walls. The
model assisted Sirius in understanding the project, but also
benefited the client by providing a pragmatic and cost-effective
approach to dealing with the project challenges.
At its deepest point the cut-and-cover section of the tunnel is
being excavated to 30 metres below the existing ground level,
and will involve excavation of approximately 400,000 tonnes of
soil, working carefully around the plethora of existing services.
Other key areas for consideration include dealing with the
ingress of water, weak and difficult soils and an old gas works
site on the river edge which in itself required contamination
clean-up as part of the preparation of the south platform. Sirius
has purchased and hired specialist equipment unique to this
project, such as a telescopic grabber and 50-tonne excavator,
along with specialist skips to recover soils from the tightest and
deepest areas of the excavation.
Given the very tight working corridor on the site, space for
The type of earth in places was thick bible clay, some of it contaminated too stockpiling is very limited. Sirius identified a number of potential
50 Solids & Bulk Handling February 2010 www.solidsandbulk.co.uk
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