Full cost of the project will be financed by these two departments and Network Rail, BAA and City of London will also contribute. Transport for London is drawing funding from the European Investment Bank.
In 2009 the enabling work phase of the project started, demolition work took place demolishing buildings including Astoria Theatre, Royal Oak Portal Taxi Facility Demolition, Demolition works for Crossrail Bond Street Station, Demolition works for Crossrail Tottenham Court Road Station and Pudding Mill Lane Portal. The enabling work contracts were awarded to different civil engineering companies.
Tunneling provides solutions to the increased urbanization, congestion and pollution in the present age but tunneling is not such an easy task with huge challenges encountered because the work is carried out under major urban cities.
The most important consideration before the start of the tunneling operation is to know the nature of the soil. In the case of soft ground tunneling, clay is somewhat easy to be tunneled into as compared to coarse-grained soils (sand and gravels). The London clay, in this regard, through which much of the Crossrail’s tunnels will pass very much supports tunneling operation. This nature of the London clay allowed the engineers to construct the rail tunnels in London as early as the 1880s. But the clay in the area itself has variable properties and the major task is to determine these fluctuations in properties by analyzing the load response of samples recovered from boreholes. The microstructure of soil reveals the presence of diatoms which have a very significant effect on the behavior of clay in terms of strength and compressibility.
‘Made ground, terrace gravels and alluvium (gravel, sand, silt, and clay), London Clay and various deposits of the Lambeth Group (sand, silt, clay) and groundwater table above tunnel roof elevations’ by Gall Zeidler Consultants (2010).The proposed system for tunneling operation in the case of Crossrail is the tube tunnel rail system in which TBM’s (Tunnel Boring Machine) is used to bore 6m tunnels followed by circular precast concrete lining jointed by bolts as in cast iron lining.