Crossrail has made a dramatic U-turn over proposals for a major tunnel under the Barbican in a bid to save the 1960s towers from sinking.
The AJ has learned that the firm, which is charged with delivering the cross-London rail link, has dropped plans to use a sprayed-concrete tunnelling method, alleged to be the controversial New Austrian Tunnelling Method (NATM), on part of the route beneath the Grade II-listed estate.
Experts warned that the method, which was linked to both the 1994 Heathrow Express cave-in and the Barcelona Metro collapse earlier this year, could threaten the Barbican centre's structural stability (AJ 17.03.05).
However, the original plans have been changed following discussions between Crossrail and the Corporation of London, which was particularly worried about plans to excavate a 'cavernous' crossover tunnel.
It is understood that the parties have now agreed that the main track-crossover tunnel is to be constructed with a horizontal piped arch technique and will be shifted towards Liverpool Street station. As a result, the cavern will lie below the Barbican's lakes and parkland rather than beneath the heavy residential units.
Joe Weiss, the Corporation's strategic transportation director, admitted he was pleased with the proposed amendments.
'The environmental statement revealed an alarming proposal to use the NATM.
The Crossrail team had probably rushed in at first.' He added: 'The plan is now to drill horizontal, intersecting piles in the shape of an arch.
It's a very robust construction and you can take earth out without it falling down.' Another bonus is that there will no longer be a need for a massive, 24-hour concrete factory in nearby Aldersgate, because the new method will rely on pre-cast piles rather than sprayed concrete.
Weiss said: 'This would have risen three storeys high outside homes and the issue caused a deep local interest.' The move has met with a guarded response from Richard Morrison, head of the Barbican Association residents' subcommittee on Crossrail, who said: 'It is good news, although we will have to see if the new plans raise any other issues.' Morrison is expecting an undertaking from the company to confirm the changes shortly.