Mumbai’s Metro-3 to get new technology for tunnelling work

European boring technology, apt for congested areas, to widen tunnels

To overcome the restrictions caused by the city’s narrow roads and congested spaces, the Mumbai Metro Rail Corporation (MMRC) will adopt new technology for its tunnelling work for Metro-3 starting this January. The MMRC will use the New Austrian Tunnelling Method (NATM) to widen the tunnels underground, so as to create additional space for stations.

The 33.5-km fully underground Metro-3 corridor is from Colaba in South Mumbai to SEEPZ in the western suburbs — a route that passes through many narrow roads and congested spaces in the city. The NATM is a modern tunnelling method appropriate for congested spaces and will be used for seven underground stations — Hutatma Chowk, Kalbadevi, Girgaum, Grant Road, Santacruz, Marol and Shitladevi. Officials said the technology is being used on a large scale for the first time in the country given Mumbai’s geographical conditions.

Ashwini Bhide, managing director, MMRC said, “The NATM technology was used for Delhi Metro for a least one station. In Mumbai, we are using this technology on a large scale for seven stations. This method is being used as the width of the road is narrower than what is required for the stations.”

Bhide said the organisation recently held four conferences for co-ordinating the work among different contractors executing the project in seven different packages. The MMRC has pressed 17 tunnel-boring machines into service for the city’s first underground metro.

The boring machines have an outer covering of 6.4m. With NATM, it will be widened by another three metres to create space for the station platforms. The tunnels will be widened by using tools like breakers and also by undertaking controlled blasting in some areas. The ₹23,136 crore project from South Mumbai to western suburbs is expected to change the face of public transportation in the city, once operational by 2021.