22-05-2013, 04:40 PM
TUNNEL CONSTRUCTION METHODOLOGY
TUNNEL CONSTRUCTION.pdf (Size: 59.33 KB / Downloads: 69)
Introduction
Crossrail requires the construction of 21km of twin bore running tunnels with
an internal diameter of 6m.
The running tunnels in the central area link the Great Western Main Line
surface rail at Royal Oak Portal with new sub-surface stations at
Paddington, Bond Street, Tottenham Court Road, Farringdon, Liverpool
Street, Whitechapel and the Isle of Dogs. From there they connect to the
existing surface rail route at Victoria Dock Portal (just west of Custom House
station) and via separate running tunnels connect to the Great Eastern Main
Line surface rail at Pudding Mill Lane Portal (just west of Stratford station).
Construction Strategy
The original tunnelling strategy developed for the hybrid Bill required sixteen
tunnel drives to construct the central tunnels from five working sites in the
central area. The longest tunnel drives planned were from the Royal Oak
Portal to Fisher Street Shaft (5.10 km in length), Hanbury Street west to
Fisher Street (3.70 km) and Pudding Mill Lane Portal to Whitechapel Station
(3.70 km in length). The remaining drives were to be driven from Hanbury
Street east to Whitechapel (0.60 km), from the Isle of Dogs east to Stepney
Green (2.17 km) and on the Limmo Peninsula west to the Isle of Dogs (1.59
km) and east to Victoria Dock Portal (0.93 km). The Thames tunnels would
start from the Plumstead portal and be driven to the North Woolwich Portal
(2.64 km) (see page 10 of the Environmental Statement – Non Technical
Summary). These drives are shown in schematic form in Annex A.
Tunnel Worksites
TBMs will be launched from the four main tunnelling worksites as follows: • two TBMs from Royal Oak Portal to the west end of Farringdon
Station;
• two TBMs from the existing launch shaft site on the Limmo Peninsula
to the east end of Farringdon Station. The current plan is to construct
a section of the Isle of Dogs Station at the west end and use this to
supply tunnel segments and provide logistic support for construction of
the running tunnels. The excavated material will continue to be
transported by conveyor through the Isle of Dogs Station and removed
from the Limmo Peninsula Shaft site;
• the two tunnels from Limmo Peninsula Shaft to the Victoria Dock
Portal will be constructed by one of the above TBMs;
• two TBMs from Pudding Mill Lane Portal to Stepney Green; and
• two TBMs from Plumstead Portal under the River Thames to the North
Woolwich Portal.
Ground Conditions
The geological conditions along the route are indicated on the section shown
in Annex C. The tunnels between Royal Oak Portal and Farringdon Station
are generally within the Lower (sandier) section of the London Clay
Formation. They may occasionally intersect the underlying Harwich
Formation and Lambeth Group. Tunnelling technology through London Clay
is well proven and most of the existing London Underground tunnels were
successfully constructed in this ground.