Simultaneous double TBM breakthrough is claimed in India for the first time by the Hindustan Construction Company (HCC)/Samsung Joint Venture, working on the Delhi Metro Phase III expansion.
The pair of 6.4m diameter TBMs broke through into Dabari Mor Station on Tuesday (5 August, 2014) to complete parallel 1,150m drives from Janakpuri West Station. The machines (TBM Riddhi and TBM Siddhi) will now be extracted for transportation to Dashrathpuri Station from where they will excavate back into the opposite headwall at Dabari Mor Station.
In total the JV is using four TBMs to complete the 4.475km section between a launch shaft at Vikarpuri - from where Phase IV operations may start following the completion of Phase III - through three stations at Janakpuri West, Dabari Mor and Dashrathpuri, and into Palam Station. The second pair of TBMs (Jantar and Mantar), supplied by Terratec, have just begun their first drive (675m), after which they will be redeployed for a final drive of 1,250m into Palam Station (Fig 1).
HCC/Samsung was awarded the CC-34 contract by Delhi Metro in February 2013. In addition to the 5.8m i.d. running tunnels, project scope includes construction of three stations.
It is believed that the only other example of a simultaneous breakthrough was recorded on the 8.6km Toronto-York Spadina subway extension in 2002.
Delhi is advancing an aggressive programme of metro expansion following completion of Phase 1 (65km) and Phase II (125km) and the airport express link (23km) in 2006, and 2011 respectively. Some 41km of the Phase III extensions and 28 stations on the total 140km and 92 station of the approved works is underground, with more than 20 TBMs expected to be in operation simultaneously to complete the bored tunnel sections. Long sections of cut-and-cover work are also included.
Phase III focuses more on the outer lying areas of the city and on connecting the long radial lines of Phases I and II with circular ring lines to help reduce travel distances and relieve congestion on existing radial lines.