Twenty of the total 52 km of tunnelling for the city’s underground Metro 3 (Colaba-Bandra-Seepz) has been completed, Mumbai Metro Rail Corporation Limited (MMRCL) officials said on Wednesday, while announcing that overall, 38 per cent work of the project is now over.
The announcement came as the project achieved its fifth milestone, when one of the tunnel boring machines (TBM) deployed achieved a breakthrough at Chhatrapati Shivaji Maharaj International Airport (CSMIA) T-2 Metro station. The TBM is a highly-mechanised earth pressure balance (EPB) device that will be used around 20-25 m below the ground to construct tunnels with a circular cross-section.
Commissioned last April, the TBM, named Wainganga 3 that began boring from Pali ground, completed its tunnelling drive of 1.31 km in a section of the project categorised as Package 7, to see light at T2 station. A statement by MMRCL said that a team of nearly 150 engineers, technicians and workers are working on the Metro 3 line, which is a 33.5-km corridor.
A senior MMRCL official said that Wainganga 3 drilled its way through rocky strata made of basalt and volcanic breccia, working for 318 days to attain the breakthrough. This particular portion passes below Mumbai Metro Line 1 station at Marol Naka and Sahar Elevated Road, on its way to T-2. The 92-m long Wainganga 3 bored, on an average, 4.2 m daily, shaping the tunnel with 937 RCC cement rings. The overall tunnelling length for the Metro 3 corridor in both directions is 52 km. Wednesday’s breakthrough was the fifth on this line.
S K Gupta, Director (Projects), MMRC, said: “We have completed 38 per cent of the overall civil work. Today, it was the fifth breakthrough for the tunnel and in all, there will be a total of 32 breakthroughs for tunnelling. There are basically major milestones for us in the course of the project.”