NHSRCL floats tender for key 21-km underground tunnel for Mumbai-Ahmedabad bullet train project

The National High Speed Railway Corporation Limited (NHSRCL) has invited bids for the construction of a 21-km-long tunnel, seven km of which will be under the sea, for the Mumbai-Ahmedabad high speed rail corridor. The tunnel will be built between the underground station at Bandra-Kurla Complex (BKC) and Shilphata in the Thane district. The 7-km under sea tunnel at Thane creek will be the first undersea tunnel to come up in the country. The last date of bid submission is January 19, 2023.

The tunnel will be a single tube tunnel to accommodate twin tracks for both up and down tracks. 39 equipment rooms at 37 locations will also be constructed. To construct this tunnel, tunnel boring machines (TBMs) with a cutter head of 13.1 metre diameter will be used. Usually 5-6 metre diameter cutter heads are used for urban tunnels used in mass rapid transit system (MRTS).

Three TBMs will be used to make about 16 km of the tunnel portion and the remaining 5 km will be through New Austrian Tunnelling Method (NATM). This tunnel will be about 25-65 metres deep from the ground level and the deepest construction point will be 114 m below the Parsik hill near Shilphata.

"Three shafts at BKC, Vikhroli and Sawli at approximate depths of 36, 56 and 39 metre depths respectively will facilitate the construction," said an officials of NHSRCL adding that inclined shaft of 42 metre at Ghansoli and tunnel portal at Shilphata will facilitate the construction of 5 km of tunnel through NATM tunnelling method.

The work on the corridor has gained momentum after the change in government in Maharashtra, with tenders, which were previously floated and withdrawn, being renewed, sources said.

Earlier, the bids for the design and construction of underground BKC high speed rail station Including cut and cover length of 467m and ventilation shaft of 66m in Mumbai was floated on July 22, 2022.

In November last year, NHSRCL had invited bids for underground tunnelling works for the project. But it was cancelled this year with officials citing "administrative reasons".

In 2019, NHSRCL had first invited tenders for the project but didn't attract anyr. It again floated tenders in November 2021. Land acquisition for the project in Maharashtra, including at BKC, had been a festering issue during the previous state government, which is also getting momentum now, sources said.