DMRC witnesses first tunnel breakthrough

Delhi Metro has completed the tunneling of the Central Secretariat – Janpath stretch, the first tunnel breakthrough of phase 3 at the Janpath Metro station site on Thursday.

It is a 909.3 metre-long tunnel starting from Chelmsford Club to the new Janpath station on the down line for the Central Secretariat to Mandi House Metro stretch. The tunnel boring machine (TBM) was lowered in the Chelmsford Club shaft on January 31 but the initial drive started on March 4.

Dr Sudhir Krishna, urban development secretary said the TBM was driven by the first Indian TBM operators and soon India will also be manufacturing TBMs.

The TBM was purchased from Herrenknecht, a German manufacturer of tunnel boring machines, and was assembled in Chennai. The tunneling has been done nearly 18 metre below the earth’s surface.

The excavated earth was deposited at the Sarita Vihar depot and forest land.

Nearly 648 rings have been inserted along with the tunneling process where each ring has five segments. Each segment is 275 mm thick and 1.4 metre high. These segments and rings are connected with the help of bolts.

“This tunnelling has been part of the construction of the three km link between Central Secretariat and Mandi House. We expect that this will help to reduce pressure on Rajiv Chowk station,” said a Delhi Metro Rail Corporation (DMRC) official.

Rajiv Chowk Metro station carries over five lakh people a day. Another TBM is working on the up line tunnel which is 898 metre long which is likely to break through in another two months.

Mangu Singh, Metro chief said the first breakthrough is always special and was satisfied that it was achieved as per the schedule.

This three km stretch, referred to as the violet line, is scheduled to begin its operations by July 2014. It will extend to Kashmere Gate.