New Delhi, Oct 5 (UNI) The Delhi Metro today achieved the fourth tunnel breakthrough by boring a 1008-meter long tunnel from INA to Race Course for its Phase-II project on Central sect-Gurgaon line.
A Tunnel Boring Machine (TBM) was used to make the tunnel, said Mr Anuj Dayal spokesperson of the DMRC.
According to him,'' The TBM was lowered in the INA shaft in May, 2008. The 1008 meters tunneling was done 12 metres below the earth surface. A total of 837 rings, each 1.2 m in length, were installed simultaneously along with the tunneling process.
Each ring has six segments and these segments and rings are connected by using bolts. Seventeen thousand four hundred and two bolts have been used on the stretch." Since the ground water level was just 12 metres below and the entire stretch is covering the VIP area, extra care was taken during the grounding process so as to prevent any seepage into the tunnel, '' he said.
For Phase-II of the Delhi Metro, DMRC would use 14 TBMs. This was for the first time in any Indian city and perhaps for the first time in any Asian city that so many TBMs would be used simultaneously for building Metro tunnels.
The second phase of the Delhi Metro would comprise about 30 kms of the underground section of which about 16 kms were to be built using TBMs.
The tunnels had been designed in such a fashion that they would be strong even after 120 years, Mr Dayal said.
The other three tunnels which were made using the same technology in the past four months included two at Hauz Khas and one at Jorbagh.
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