The Hindu : Front Page : Another tunnel, another wonder

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Sunday, Jun 01, 2008
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Another tunnel, another wonder

Staff Reporter

Using state-of-the-art technology, Delhi Metro railway moves ahead

– PHOTO: SANDEEP SAXENA

MOVING AHEAD: Inside the brand new Delhi Metro railway tunnel on the upcoming Malviya Nagar-Hauz Khas underground section on Saturday.

NEW DELHI: The Delhi Metro railway has done it again – and well ahead of time again. Working its way through tonnes of soil and silt, the larger-than-life Tunnel Boring Machine that was lowered underground at Malviya Nagar in South Delhi on the upcoming new Central Secretariat-Qutub Minar metro line this past December emerged at Hauz Khas on Saturday after carving out a 1,450-metre-long tunnel.

The machine was lowered into the Malviya Nagar shaft on December 5, and following its assembly underground the tunnelling operation started on January 4. According to Delhi Metro Rail Corporation officials, the initial drive of 60 metres was completed in 18 days flat while the main drive was taken up on February 1 and the breakthrough achieved on Saturday -- almost a week ahead of schedule.

A German laser system was used to guide the TBM along its precise alignment. During the tunnelling process, about 42,000 cubic metres of earth was excavated. This was deposited in Delhi’s low-lying areas at Sarai Kale Khan and Satpula.

Since the tunnel ran below thickly populated residential areas of Begampur village and Sarvapriya Vihar, a building condition survey was carried out before starting the tunnelling work 30 metres on either side of the tunnel alignment. “During the tunnelling operations, intensive monitoring above the ground was done using inclinometers, strain gauge load cells, settlement points, building points, reflectors, etc.,” said DMRC officials.

The DMRC is also constructing a parallel tunnel using another TBM which is expected to finish the job in about a month from now. Both the TBMs will then be dismantled, taken out and lowered through another shaft at Hauz Khas from where they will tunnel their way further towards Green Park.

For its Phase II construction the DMRC would be using as many as 14 TBMs. This is the first time so many TBMs would be used simultaneously for building metro railway tunnels in any Indian city. The second phase of Delhi Metro comprises about 30 km of underground section of which about 16 km is to be built using TBMs.

According to DMRC officials, all the TBMs would finish the tunnelling work by December 2009 after which electrical, signalling and other works will start. The TBM progresses about 300 metres in a month depending on the type of soil.

Among those who watched the TBM emerge after accomplishing the tunnelling job on Saturday were Delhi’s Lieutenant-Governor Tejendra Khanna, DMRC Chairman M. Ramachandran and Managing Director E. Sreedharan.

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