First Tunnel Breakthrough Of Phase - III At Janpath Metro Station
The DMRC today completed the tunneling of the Central Secretariat (CTST) – Janpath stretch with the first tunnel breakthrough of Phase – III at the Janpath Metro station site.
The Tunnel Boring Machine (TBM) emerged at the 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 31st January, 2012 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 4th March 2012.
The tunneling was done almost 18 metres below the earth’s surface. The excavated earth was deposited at the Sarita Vihar Depot and Forest Land. Earth Pressure Balancing Type TBM was used to concrete the tunnel. The TBM cutter head rotated at the rate of 2 to 2.3 RPM.
A total of 648 rings have been inserted simultaneously along with the tunneling 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 internal diameter of the tunnel is 5.8 mts. The casting of the segments was done at the Mundka Casting Yard.
The tunnel is lined with reinforcement of concrete segments of M-50 concrete. The total concrete required for lining was 4768 cum and reinforcement / steel required 334 MT. For stability, 3100 cu. mts. of grout was filled behind the rings.
31, 000 cub excavation was done in 125 working days.
The TBM used to make the tunnel is from Herrenknecht and was assembled at Chennai before being brought to Delhi.
This TBM was driven by Mr. Mohd. Ali who is India’s first TBM Operator and was assisted by Sh. Ram Avtar Singh Rana.
The instruments used for ground and structure monitoring were: MPBS, Stand Pipe Piezometer, Vibrating Wire, Piezometer, Crack Meter, Tilt Plate, Soil/Pavement Point, Building Settlement Point and Bireflect Target.
M/s Pratibha CRFG JV is the contractor for the tunneling work of the stretch from Central Secretariat to Mandi House metro station. The stations at Janpath and Mandi House are also being constructed by the same contractor using Cut & Cover technique.
Another TBM is working on the Up Line. The Up Line tunnel is 898 mts long and is expected to breakthrough in another two months. This is the first tunneling activity of the Phase III construction.
This 3 kms stretch is an extension of the Central Secretariat - Badarpur corridor (Violet Line) and is scheduled for opening in July 2014. This corridor will further extend to Kashmere Gate and will have two interchange stations at Mandi House and Kashmere Gate.
Dr. Sudhir Krishna, Chairman, DMRC was present at the site during the breakthrough alongwith Shri Mangu Singh, Managing Director, DMRC.
Dr. Krishna congratulated the entire DMRC team and said that such engineering feats boost the self confidence of our civil engineers and place them on a high pedestal. He said that this TBM was driven by the first Indian TBM Operator and soon India will also be manufacturing TBMs. Dr. Krishna also praised the DMRC work culture and said that DMRC has taught a lesson to everybody in how to work in coordination with all departments of engineering like civil, mechanical, electrical alongwith, signaling and telecom, property development, etc.
Shri Mangu Singh said that 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 and congratulated the DMRC engineers and the Contractor for achieving this milestone.