Eight TBM ladies set the pace in London tunnel marathon

London is actually the cradle of modern tunnelling. Here in 1825 the first successful crossing under a river began using mechanized tunnelling construction. In order to master the soft sandy ground under the Thames the architect Marc Brunel and his son Isambard Kingdom Brunel designed a special steel frame. In its protection workers dug the tunnel, while right behind them masons reinforced the walls with bricks. This was the birth of shield tunnelling machines. The Thames tunnel took 18 years to complete – an extraordinary pioneering achievement at the time.

The principle of supporting the tunnel face in soft soils and expanding the tunnel in the protection of a shield has remained. Nowadays, however, tunnel boring machines with diameters of up to 19 meters drill through the ground. With modern tunnelling technology pioneer structures of quite a different dimension are created. Right at the forefront in this respect is the Crossrail project in London, a three-year tunnelling marathon that has now successfully completed.

With the breakthrough of the Herrenknecht tunnel boring machine (TBM) named "Victoria" on May 23, London again made tunnelling history. Victoria is the last of eight Herrenknecht TBMs which together have dug 42 kilometers of tunnels right through the heart of London. The team of Victoria, Elizabeth, Phyllis, Ada, Jessica, Ellie, Sophia and Mary worked at tremendous speed.

At the official breakthrough celebrations on June 4, UK Prime Minister David Cameron said: "Crossrail is an incredible feat of engineering that will help to improve the lives of working people in London and beyond. The project is a vital part of our long term plan to build a more resilient economy by helping businesses to grow, compete and create jobs right along the supply chain."

Crossrail forms a major new east-west connection through the congested metropolis of eight million inhabitants. Five twin bore tunnels with a total length of 21 kilometers and ten new stations link existing railway networks to the east and west of London. The new railway will stretch from Reading and Heathrow in the west through central London to Shenfield and Abbey Wood in the east.

Andrew Wolstenholme OBE, Crossrail Chief Executive, praised the teams on the completion of the work: "Crossrail is being delivered on time and within budget and will transform how people travel across London. Over the last three years, our highly skilled team have worked tirelessly to build these major new tunnels under one of the world’s busiest cities. The challenge now shifts to the complicated and substantial task of fitting out the tunnels and stations to enable Crossrail services to operate.”

Machine technology and service from a single source

Project owner Crossrail Ltd (CRL) commissioned three joint ventures with the construction of the five tunnel sections: Bam/Ferrovial/Kier JV with the Western Tunnels, Dragados/SISK JV with the three sections of the Eastern Tunnels and Hochtief /Murphy JV with the Thames Tunnel.

All three joint ventures relied 100 percent on technology from Herrenknecht, the leading provider of holistic solutions in mechanized tunnelling. The company from Schwanau in Baden-Württemberg/Germany supplied six Earth Pressure Balance Shields (EPB) for the construction of the eastern and western tunnels through London clay, sand and gravel. Two Herrenknecht Mixshields excavated the Thames Tunnel at depths of up to 15 meters below the river bed.

At depths of up to 40 meters the tunnel boring machines made their way under some of the most expensive real estate in the world past existing metro lines, sewerage, supply and disposal channels as well as building foundations. The machines with a shield diameter of 7.08 meters are 147 meters long, weigh up to 1,100 tonnes and have a drive power of up to 1,920 kW. For precision targeted control all eight machines were equipped with navigation systems from Herrenknecht subsidiary VMT.

Operated by 20 men per shift, twelve men on the TBM, eight on the gantry and above ground, the machines drove 24 hours a day, seven days a week. They achieved impressive advance rates of up to 72 meters (45 segment rings) per day.

Such performances result from perfectly coordinated cooperation between all project participants. "Herrenknecht doesn't just sell a machine and then only leave a phone number. The Herrenknecht people are actually always on site: I have a contact any time I need one," notes Roger Escoda, Tunnel Manager Dragados/SISK Joint Venture.

Herrenknecht supplied the machines together with comprehensive service solutions. These included assistance with the assembly and disassembly of the TBM at the jobsites, the provision of jobsite personnel to support the advance and the supply of cutting tools and spare parts. In addition, together with the customers Herrenknecht developed individual solutions, for example for disassembly in confined shaft conditions, for pulling machines through stations as well as the transport planning for the second use of two TBMs on another section.

"The Crossrail project demonstrates how very good organization and the close cooperation of the individual specialists make it possible to realize projects of this enormous construction logistics complexity within very demanding timelines and binding budget plans with maximum safety," concluded Dr.-Ing. E. h. Martin Herrenknecht, founder and Chairman of the Board of Management of Herrenknecht AG, on the successful completion of the tunnelling.

Crossrail - Europe's largest infrastructure construction site

Crossrail will be a new 118km metro railway from Reading and Heathrow in the west to Shenfield and Abbey Wood in the east via central London. The route connects 40 stations, ten of which are new. The journey time from London Heathrow to the main financial centre in the City of London (Liverpool Street) is shortened from 55 to 32 minutes. 200 million passengers per year are expected.

To deliver Crossrail project up to 10,000 workers are active on more than 40 jobsites. Construction started in 2009, the start-up is scheduled for the end of 2018. The total costs amount to approximately € 20.8 billion.

You can get a deeper insight in our jobsite feature in the second edition of the All Around Online magazine here!

 

More News and Articles