Mumbai Metro Rail Corporation bores 50% tunnels of Metro-3 in 19 months

India's only underground metro on the Colaba-Bandra-Seepz called as Mumbai Metro 3 has achieved a major milestone. The Mumbai Metro Rail Corporation (MMRC) has bored 50% of the tunnel in 19 months. The remaining 28 km will be bored and tunnelled before June 2020. At least 56 km of tunnels will snake below the surface for the 33.5-km long metro rail alignment. The 56-km is both Up and Down lines on which then tracks will be laid. At some locations, the alignment comes at grade or leads to shafts.

MMRC sources said that the tunnelling work of the project started in November 2017. "Tunnelling is comparatively easier as the thickness of basalt rock throughout the route is more or less similar. The time-consuming work of building stations has begun," said an MMRC official. The authorities are inspecting the alignment of the tunnel – checking if the TBM has diverted from the actual route - every few meters. The shift is barely 2mm.

The officials said that tunnelling under Mumbai's heritage buildings, old residential complexes, and existing elevated metro line with different geological conditions has been a daunting task. Ashwini Bhide, managing director, MMRC said, "The work of underground station construction along with excavation, base slab, concourse slab, columns and wall construction is also progressing fast."

After launching Krishna-1, the first TBM at Naya Nagar, Mahim in September 2017, MMRC has been working full steam with the help of total 17 TBMs. The tunnelling activity began in November 2017. The first breakthrough on the alignment was achieved in September 2018. The authorities achieved 12 more breakthroughs in the next 8 months, until May 2019.

There are 12 launching shafts to facilitate tunnelling at Cuffe Parade, Eros Cinema, Azad Maidan, Science Museum, Siddhivinayak, Naya Nagar, BKC, Vidyanagari, Pali Ground, Sariput Nagar, Sahar Road and International Airport T2 terminal. The longest tunnel so far has been the tunnel from Vidyanagari to Domestic Airport (3.9-km) and the shortest one is from Sariput Nagar to SEEPZ (562 meters). In all, 19,504 segment rings have been used to complete 28-km of tunnelling. These segment rings are manufactured at 6 casting yards – 4 at Wadala and one each at Mahul and Jogeshwari-Vikhroli Link Road. Further 19 more breakthroughs are awaited through the 33.5-km long Metro-3.

In Numbers

• 13: Breakthroughs accomplished
• 19: months taken for tunnelling
• 17: Total number of TBMs used
• 3.9-km: Longest tunnel from Vidyanagari to domestic airport
• 562 meters: Shortest tunnel from Sariput Nagar to Seepz
• 19: No. of breakthroughs to be completed in coming months
• 33.5 km: Distance of Metro 3
• 27: No. of stations
• Rs 30000 crore: Project cost

Areas covered: Speez, CSIA T2, Sahar station, MIDC, Domestic Airport T1, Dadar, Worli, Vidyanagari and Vidhan Bhavan.