Crossrail’s Uphill Excavator

Uphill excavator

Crossrail is one of the largest construction projects in Europe and is considered to be an exemplary project by many contractors working on it.

Construction of London’s €17 billion Crossrail railway project began in 2009. At the centre of the project are 21 kilometres of new twin tunnels bored deep under London, through clay terrain already riddled with underground rail lines and sewers. Currently, rail passengers wanting to travel from towns to the west of London to a town to the east of London, it is necessary to change trains and get a local Tube train or bus between mainline railway stations. When Crossrail opens in 2018, trains will be able to run directly east- west through the city. Crossrail is the name of the project and the client organisation, but the line is to be called the Elizabeth Line.

A report by two of Europe’s biggest construction companies says that Crossrail is a good example of best practice in construction innovation. Balfour Beatty of the UK and Vinci of France have worked together in joint venture on numerous major projects, including the Channel Tunnel and parts of Crossrail. Their report, Innovation for the Future – Better Delivery of Mega Projects, sets out the lessons that they have learned and their recommendations for successful project delivery.

The report says that clients too often seek to manage risk by making a plan and getting contractors to stick to it religiously.  But sometimes they should leverage the ingenuity of contractors, says the Balfour Beatty Vinci joint venture team.

“Challenging the status quo of existing technology should be promoted where possible, as it can lead to important savings,” their report says.

“Too often though, the temptation for those running the bidding process is to control risk by using tried and tested methods. The exception to this has been Crossrail, where a novel approach, known as ‘optimised contractor involvement’ was developed and introduced,” the report says. “This was one of the processes introduced by the Crossrail Innovation Forum, a dedicated team set up to drive and oversee innovation.”

A good example of the innovation introduced by contractors on the Crossrail project is the uphill excavator, designed and constructed by GTA Maschinensysteme GmbH. It had never been used anywhere in the world before and was developed specifically for this assignment.

“The on-site team realised that the ability to excavate upwards from existing tunnels at the base of the escalator shaft would generate significant time and cost savings over the normal process,” explains the Innovation for the Future report. “In response, the Balfour Beatty Vinci and Morgan Sindall joint venture, BBMV, introduced a bespoke uphill excavator that is suspended from the ceiling of the construction tunnel and advances in line with the tunnel progression.”

Excavator

Traditional uphill excavation is considered unsafe due to the risk of excavated material falling onto the excavator and workers. But the contractors realised that the ability to excavate upwards from existing tunnels at the base of an escalator shaft would save a lot of time, and therefore also money.

The working boom is equipped with a quick coupling system that allows it to be reconfigured quickly for different situations on site.  The uphill excavator also has a built-in shotcrete manipulator.

Austrian engineer Thomas Wechner was involved in this part of the project and he has written about it on the official Crossrail blog site. “The most challenging part of my time so far on the project was the planning, preparation, set-up and supervision of the uphill excavator that we used to construct our escalator shafts,” he recalls. “This bespoke machine was specifically developed for this Project and was the first time that the technique has been used worldwide. At each stage, all procedures were developed from scratch, the requirements from each of the different designers coordinated and, most importantly, the site team briefed for this new unique process. Seeing the first uphill drive successfully completed makes me feel extremely proud and satisfied.”

So successful was its use, the uphill excavator was then moved onto other parts of the projects, for other escalator shafts.

There is a video that shows the GTA uphill excavator at work on Crossrail shafts.

 

Steve Rhine

About Steve Rhine

Community Manager at MachineryZone USA - All latest construction news on MachineryZone Mag!