ANOTHER SIGNIFICANT piece in Heathrow Terminal 5's underground jigsaw is in place with the breakthrough of the first of two tunnels forming the Heathrow Express Extension (HexEx).This marks the first physical connection between T5 and Heathrow.
The breakthrough was made into a headshunt, stretching for 150m beyond the existing line, built as part of the original Heathrow Express as provision for potential extension to the west of the airport.
Morgan Vinci and Mott MacDonald carried out the work using a 150t, 61m Dosco open face TBM, taking four and a half months to excavate the 5.7m diameter, 1.6km tunnel.
At one point the TBM passed just 3m beneath the London Underground Piccadilly Line. Real-time electronic monitoring ensured no unexpected movement of the lining.
Ian Fugeman, T5 head of rail and tunnels said: 'T5's basic tunnel infrastructure is now almost complete, with eight of nine T5 tunnels successfully bored.'
The TBM was dismantled underground and is now on the second upline tunnel towards London and is due to be finished early next year.