Work to build the first two of five planned metro lines in the Chinese city of Wuxi has reached a milestone with 16km of tunnels completed by a fleet of eight tunnel boring machines (TBMs) in just 20 months.
The first of the eight 6.3m diameter earth pressure balance machines was launched in July 2011 by Wuxi Metro Group and the fleet has achieved tunnelling rates of up to 33m a day and 164m a week to complete the new tunnels despite challenging ground conditions.
The tunnels were being constructed with small overburdens in some areas and close to exisiting building foundations. Ground cover on metro line 1 was as little as 7m in some places and the tunnel also passed just 3.7m below piled foundations, so ground freezing was used to minimise ground movements.
Wuxi’s metro lines 1 and 2, with a total length of 58.5km, are expected to start operation by the end of 2014. Line 1 crosses the city from north to south, and line 2 from east to west.
The city, which has a population of 4M, is planning to increase the network with three further metro lines.