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Blackwall Road Tunnel, southbound
Poplar to Greenwich, London, UK
associated engineer
Mott Hay & Anderson
Hugh Iorys Hughes
date  1958 - 1967, opened 2nd August 1967
era  Modern  |  category  Tunnel  |  reference  TQ383807
ICE reference number  HEW 2202/02
The second Blackwall Tunnel, which takes road traffic south under the River Thames, was completed 70 years after the first one. It was needed to alleviate congestion on the route. The original approach roads were re-aligned to facilitate access to both tunnels. Blackwall is the furthest downstream toll-free fixed road crossing of the River Thames, and is in continual use as part of the A102.
The first tunnel, which opened in 1897, was designed for horse-drawn vehicles. By the 1930s, its two narrow lanes were becoming inadequate for the volume of traffic. As early as 1937, London County Council decided the solution was to build a second tunnel parallel to it.
The London County Council (Tunnel and Improvements) Act was passed on 29th July 1938. It authorised construction of the new tunnel, and acquisition of land for approved road improvements and new roads necessary on the north side of the river. It also enabled demolition of the 1897 entrance gatehouse on East India Dock Road and the Tunnel Gardens east of Robin Hood Lane.
However, World War II (1939-45) and subsequent economic austerity delayed the project. In 1957, the Ministry of Transport allowed the council to start work on the northern approach. The winning tender was for £570,191. Construction began in April 1958 and the new road layout opened on 27th June 1960.
Work began on the new tunnel bore in the same year. It is about 210m downstream (north east) from the first tunnel and is 1.175km from portal to portal, with an internal diameter of 8.6m. Unlike the earlier tunnel, it has no sharp bends but does follow a smooth curve at each bank.
The route was influenced by the locations of suitable sites for the two caissons that provided access for the tunnelling shields and become permanent ventilation shafts. The northern shaft (TQ385806) is in the former Midland Railway’s dock, south of Blackwall Way, and the other (TQ390800) is on the site of the Eastern Gas Board works at Greenwich, now occupied by the O2 Arena.
The two sites were cleared and bulk excavated to remove made ground, buried tree trunks and other detritus. Construction and sinking of the caissons (rectangular boxes of concrete and steel plate) began in the sound subsoil some 9m below surface level, inside a steel sheet piled cofferdam. This technique provided greater control over the lowering operation, and almost eliminated the risk of exposure to potentially dangerous ground gases. The caissons were sunk onto mass concrete pad foundations.
Before tunnel boring could commence, water-bearing ground strata had to be chemically stabilised and grouted to minimise the possibility of excavation collapse. The caissons were used to assemble the two Greathead tunnelling shields that were employed. These same shields had been used to constructing the first Dartford Tunnel (1958-63), also engineered by Mott, Hay & Anderson, and were reconditioned for use at Blackwall.
Each cylindrical steel shield had compartments at the front that allowed up to 12 people to excavate the rock face simultaneously, working in a compressed air environment. The shield was driven forward into the bore by hydraulic rams, and cast iron tunnel lining rings installed in the space created. The two shields met, completing the subaqueous part of the tunnel, in May 1964.
The cast iron tunnel tube was lined with PVC-coated aluminium sheeting, grey on the walls and blue on the suspended ceiling. A variety of finishes has been used, including Portland stone, precast tiled panels and black terrazzo coping.
Landward of the two caissons, the tunnel was constructed in cut-and-cover trenches for which watertight reinforced concrete was used. The open approaches leading to the tunnel were designed by the council chief engineer’s department, assisted by consulting engineer Hugh Iorys Hughes (1902-77).
A two-storey concrete frame administration building (TQ384808) was built between the northern approach roads of the old and new tunnels, with traffic control offices over a maintenance vehicle depot.
After tunnel boring was completed, the caisson shafts became ventilation shafts. To run them, four ventilation fans, motors and associated equipment are housed in a pair of above-ground shell structures on top of the shafts, designed by architect Terry Farrell (b.1938) in 1961-2 and constructed 1964-7.
Each structure consists of a pair of asymmetric towers joined at the base, curvilinear in form. Their shape was influenced by the pattern of aerodynamic airflow exhausted from the fans. The shells are are composed of prestressed cable frameworks anchored to concrete ground slabs, with sprayed concrete cladding. Airlocks in the shafts provide access to the tunnel below.
The project’s safety record was far better than that of the 1897 tunnel (seven deaths), though the dangers of working in compressed air were undiminished. Here, there were no fatalities and 1.06% of tunnellers suffered from the bends. In the 1960s, the risk of bone necrosis as a result of decompression was still being investigated but it was thought that as many as 20% of workers could suffer bone defects later in life. Consequently, the second Dartford Tunnel bore (1980) was one of the last to use large-diameter Greathead tunnelling shields with compressed air.
Desmond Plummer, Leader of the Greater London Council (successor to London City Council) opened the second Blackwall Tunnel on 2nd August 1967. The final construction cost was around £7m. The opening ceremony also marked the inauguration of separate work on the southern approach (completed in 1969), and the temporary closure of the original tunnel for refurbishment.
The new tunnel carried two-way traffic until 4th April 1969, when the first tunnel re-opened. It now takes southbound traffic, while the old tunnel carries northbound traffic.
When the Millennium Dome (now the O2 Arena) was built in Greenwich in 1997-9, its superstructure was specially shaped around the southern ventilation tower (TQ390800). Both tunnel ventilation towers were Grade II listed in December 2000.
In 2002-4, Fitzpatrick carried out a £15.4m refurbishment of the newer tunnel for Transport for London. Work included installing new lighting, wall cladding, fire fighting equipment, emergency telephones and providing a new maintenance walkway.
Resident engineer: Jasper Kell
Contractor (northern approach roads): Holland, Hannen & Cubitts
Contractor (northern approach roads, 2002-4): Fitzpatrick & Son
Contractor (tunnel): Balfour Beatty & Co Ltd
Contractor (cut-and-cover): Kier Ltd
Contractor (admin building and ventilation towers): William J Jerram
Architect (ventilation towers): Terry Farrell
Ground treatment: Cementation Company and Soil Mechanics-Soletranche Ltd
Ventilation plant: Midland Heating & Ventilation Co
Tower shells: The Cement Gun Company (with Flint & Neil)
Research: ECPK
"Blackwall Tunnel Duplication" by Jasper Kell and Gordon Ridley, in ICE Proceedings, Vol.35, pp.253-274, London, October 1966
"Discussion. Blackwall Tunnel Duplication" by Jasper Kell et al, in ICE Proceedings, Vol.37, pp.537-555, London, July 1967
reference sources   CEH Lond

Blackwall Road Tunnel, southbound