Second tunnel boring machine starts digging under Sanjay Gandhi National Park for GMLR

A key milestone has been reached in the Goregaon-Mulund Link Road (GMLR) project in Mumbai. The second tunnel boring machine (TBM), 'Vihar', began excavation on November 7, according to an official statement.

Excavation of both tunnels under Sanjay Gandhi National Park has now begun. The first TBM, 'Tulshi', has been working since August 17, 2026, and has so far excavated more than 270 metres.

The Brihanmumbai Municipal Corporation said the second machine will let work on both tunnels proceed simultaneously and speed up construction. The project aims to significantly cut travel time between Mumbai's eastern and western suburbs.

GMLR is a 12.20-km project. Under its Phase 3(B), the civic body is building two twin tunnels under Sanjay Gandhi National Park, between Dadasaheb Phalke Chitranagari in Goregaon East and Amar Nagar in Mulund West. Each tunnel is 5.34 km long and will be built using TBM technology.

'Tulshi', the first machine, went into operation on August 17 after technical processes and trials were completed. It is excavating towards Mulund at an average of about six metres a day. Depending on progress, the civic body plans to raise this in stages to 10 metres a day. 'Vihar' began excavation after successfully completing its Site Acceptance Test.

Like 'Tulshi', 'Vihar' uses single shield Earth Pressure Balance (EPB) technology. Its cutter head has a diameter of 14.49 metres and the whole machine is 83 metres long, with a 22-metre shield section and a 61-metre, three-storey backup gantry. EPB technology keeps soil pressure at the excavation face under control, keeps the ground stable and allows the tunnel to be built in a controlled and safe manner.

In the Site Acceptance Test, the machine's mechanical, electrical, hydraulic and control systems were checked against the prescribed technical criteria. It was also confirmed that all equipment and safety systems are ready for actual excavation.

Each twin tunnel will be 6,675 metres long in all. Of this, 5,340 metres will be excavated by the TBM, while the remaining 1,335 metres will include box tunnels, entry and exit ramps and shafts. The internal diameter of the tunnels will be 13 metres. Each tunnel will have three traffic lanes, making six lanes in total across both directions. Both machines will dig from Goregaon towards Amar Nagar in Mulund West. When complete, the eastern and western suburbs will get a direct underground link, reducing dependence on existing roads. The civic body aims to complete the entire GMLR project by February 2029.

Rehabilitation and demolition are also under way at the Mulund end, where a retrieval shaft and ramps are being built. According to the civic body, 743 structures are affected by the proposed work, of which 612 have been demolished so far. The remaining 131 are expected to be demolished by the end of December 2026 or early January 2027. Affected families will be rehabilitated in buildings at Kanjurmarg, where work is in the final stage.

Additional Municipal Commissioner (Projects) Abhijit Bangar said that with 'Vihar' starting excavation while work on 'Tulshi' continues, both tunnels will advance together and construction will gain pace. He has directed the agencies concerned to take the necessary steps to avoid delay and to regularly review construction progress, machine availability, technical requirements and manpower. Additional manpower and technical staff will be deployed where needed.

Bangar also said that the safety of workers and engineers must remain the priority in this technically difficult excavation. Contractors have been instructed to follow safety standards strictly, provide the necessary protective equipment and put preventive measures in place against possible hazards. Emphasis has also been laid on proper transport and disposal of excavated soil, or muck, and on keeping the construction site and its surroundings clean.