...interest. Being in the same TfL “family” should ease interfaces between Crossrail and the city metro operator, London Underground Ltd., hopes Oakervee. And letting the national railroad owner, Network Rail, handle work on its system should reduce boundaries further.
Nevertheless, RLE Technical Director Mike Glover fears Crossrail’s interfacing problems my be “10 times” greater that theirs. Time taken in dealing with Network Rail and other interested parties was excessive and “particularly too expensive on management time,” he says. “Everything comes under an intense degree of focus.”
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Courtesy of Cross London Rail Links Ltd.
Few aspects of Crossrail will be more closely observed than its impact on the buildings above it. Oakervee was already aware of the potential of tightly specifying tunnel-boring machines (TBMs) to limit surface settlement, but HS1 “was the first time it was demonstrated in London,” he says.
Following CTRL’s lead, the Crossrail team will set high specifications for its seven TBMs. “We don’t want the machines to be a fundamental part of the tunnel contractors’ price,” Oakervee explains.
On HS1, RLE also set a minimum specification, rather than allowing contractors to decide on the basis of geological data, says Blight. “We knew what the best TBM was....We went to consult with contractors and TBM manufacturers,” he adds.
Apart from a slurry machine working mainly in chalk under the Thames, HS1’s other seven TBMs were of the earth-balance pressure type. Some of them were able to function in open mode. But “we used the TBMs in their closed mode to reduce settlement,” says Blight.
To minimize TBM pick wear and surface settlement, the HS1 project extended dewatering to include all its London tunnels, says Blight. Originally, only the huge station box at Stafford and the line’s five ventilation shafts were to be dewatered.
Crossrail TBMs west of Farringdon will work in London clay, a well-travelled and good tunneling medium, notes Oakervee. Further east, the route touches on trickier territory, cutting into gravels, alluvium and water-bearing sands. Apart from a slurry machine under the Thames, all Crossrail machines will be earth-pressure balanced.
Crossrail’s tunnel spoil will be removed by rail from the west portal and on barges from the east end, says Oakervee. Eliminating more costly and disruptive road disposal was made possible by rescheduling station work, he adds. Even station spoil may be taken out by underground routes he hints, saying discussions are at an early stage.
As Crossrail prepares to take off, its future seems sure to be touched by preparations for the 2012 Olympic Games, now heating up in east London. Games-related construction, budgeted at over $16 billion and due for completion 2011, will compete for resources.
RLE “had a lot of pressure from competing projects” in recruiting and retaining staff, says Sedar. “We had people from around the world working on this,” he adds. He estimates 30% of the technical staff was international.
But Balfour Beatty Construction, a major U.K. civil engineering and railroad contractor, is not worried. “The impact of Crossrail will be less significant than people would expect,” says CEO Ian Tyler. “Contractors have their ability to flex their resources...Where the crunch will come is going to be in the management [resources], as ever.”
With their controversially ballooning budgets, the Olympic Games will strengthen CLRL’s resolve to control its costs. The $32-billion price tag, in money of the day, “can come down but it can’t go up,” says Oakervee.
Oakervee takes comfort from the huge library of knowledge gathered on the project since it took off nearly 20 years ago. Costs have been audited both by Bechtel and by Nielsen-Wurster Group Inc. Princeton, N.J. Additionally, says Oakervee, CLRL’s operations team reviewed the project to ensure “we were designing a railroad, not an engineering masterpiece.”