MMRC builds 270 metre Tunnel under Mithi River

Mumbai’s fully underground Metro-3 corridor from Colaba to Seepz has crossed the Mithi river’s main water channel. Of the 1.18km tunnels being built between the Bandra-Kurla Complex (BKC) and Dharavi station, 270 metres (m) come under an active river channel, which has been crossed, said Mumbai Metro Rail Corporation (MMRC) officials on Thursday during a media visit to the BKC and Cuffe Parade Metro stations. The remaining work is expected to be completed by the end of March.

“Of the two tunnels, one tunnel has achieved 87% progress, while another has achieved 65% progress. However, we have already crossed the active river channel. We are also tunnelling almost 10m every day, so we aim to finish the rest of the work in a month’s time,” said SK Gupta, director (project), MMRC.

By active river channel, he was referring to the portion of the river where water continuously flows, making it the most challenging part to tunnel under. The remaining area above the tunnels includes marshy land and mangroves, which get flooded during high tide.

The 33.5 km Metro-3 corridor (Colaba-Andheri-Seepz) will be the second Metro in the country to have tunnels under a riverbed. The first one is being constructed in Kolkata under Hooghly river.

To prevent water seepage between the segments of the tunnels, MMRC is using special gaskets that swell when they come in contact with water. A segment is used to form the rings of the tunnel. Each ring has about six segments in it.

At present, the business hub of BKC, which is not connected with existing suburban lines, will be the largest station along Metro line 3 (474m in length). This station will be a crucial intersection point as it will be a three-line station with two main platforms, a cross-over line which will connect to either side of the mainline, and two stabling lines.

The cross-over line is being constructed using the new Austrian tunnelling method (NATM), a more conventional method of tunneling. As of January, 40% of the station works in BKC was completed.

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