Over 90 per cent of construction work on the 4.29-km Dwarka-Najafgarh section of the Delhi Metro has been completed and passenger services on the stretch are expected to begin by September, officials said Thursday.
Also, the work on the Najafgarh-Dhansa Stand section using a Tunnel Boring Machine (TBM) also started Thursday, which will bore a 700 m-long tunnel in the 1.2 km-segment, they said.
The Najafgarh-Dhansa Stand section is an extension of the Dwarka-Najafgarh segment.
"The work for the Dwarka-Najafgarh section was formally awarded in late 2017 and the target date for completion is December 2020. On this section, over 90 per cent of the construction work has been completed and passenger services are expected to start by September," the DMRC said in a statement.
A DMRC spokesperson said the TBM first used on the up line will be subsequently used for tunnelling on the down line between the same stations.
The entire tunnelling work on both the up and down lines will be completed by September this year, he said.
The Najafgarh-Dhansa Stand stretch is entirely underground. While 700 m of it will be constructed using the TBM, the rest will be done using 'cut and cover' technology in which excavation is done for underground construction and then the area is covered again, the DMRC said.
As part of its third phase of expansion, the DMRC has constructed close to 54 km of underground sections, which is more than the span of such sections constructed in its first and second phases, the DMRC said.
"About 30 TBMs were put into use for carrying out such massive underground tunnelling work. It was a tremendous engineering challenge since Delhi is an extremely crowded city and tunnelling had to be done beneath centuries-old buildings and congested localities," the statement said.
TBMs were introduced for the first time by the DMRC during the first phase of metro construction work. In Phase-II of the Delhi Metro, 14 TBMs were used while in Phase-III, the number of such machines used was 30, it added.
The Delhi Metro currently operates a network of 327 km with 236 metro stations. This network includes over a 100 km of underground lines spread across the national capital, it said.
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