The Tunnel Boring Machine (TBM) emerged at Janpath metro station site after making a 909.3 metre-long tunnel from Chelmsford Club on the Down Line.
"This TBM was lowered in the Chelmsford Club shaft on January 31 and after assembly of the TBM below the ground. The TBM broke through from the South Shaft of the Janpath Metro station close to the Chandralok building. The initial drive began on March 4," Delhi Metro spokesman Anuj Dayal said.
The tunnelling was done almost 18 metres below the earth's surface and the excavated earth was deposited at the Sarita Vihar Depot and forest land.
The breakthrough was achieved in the presence of Urban Development Secretary Sudhir Krishna, Chairman and Delhi Metro chief Mangu Singh.
Krishna congratulated the entire DMRC team and said such engineering feats boost the self confidence of "our civil engineers and place them on a high pedestal."
Mangu Singh said the first breakthrough is always special and significant. He expressed satisfaction over the fact that this breakthrough was achieved as per schedule and without any bottlenecks.
The tunnelling was part of the construction of the 3 km link between Central Secretariat and Mandi House. The station is expected to reduce pressure on Rajiv Chowk, which handles more than 5 lakh people a day.
A total of 648 rings have been inserted simultaneously along with the tunnelling process. Each ring has five segments (each 275 mm thick) and the length of one segment is 1.4 mts. These segments and rings are connected by using bolts.
The TBM used to make the tunnel is from Herrenknecht and was assembled at Chennai before being brought to Delhi. The TBM was driven by Mohd Ali who is India's first TBM Operator and was assisted by Ram Avtar Singh Rana.
