As part of its third phase of expansion, Delhi Metro is constructing over 53 kilometres of underground Metro lines comprising of 74 different tunnelling drives of about 37km. Some 35 TBMs are to be used for this mammoth assignment during the entire third phase and about 21.kilometres of tunnels (or 41km of tunnels including up and down tunnels) and 33 tunnelling drives have already been completed so far. The entire tunnelling work of Phase 3 is expected to be finished by the end of 2015.
The use of 19 TBMs simultaneously within the confines of one city is among the highest used anywhere in the world. In Phase 2, Delhi Metro had used a total of 14 TBMs during the entire span of work.
For the current phase, so many TBMs are being used because the proportion of underground construction has increased significantly compared to the last two phases. While, Delhi Metro currently has an operational underground section of approximately 47km, the third phase alone will alone have over 37km underground.
