Bullet Train Project: Underground, Undersea Tunnel Work In Maharashtra Going Great Guns

After slow progress initially, work in Maharashtra for the bullet train project is underway in full swing now. Last month, the NHSRCL invited bids for the ‘Design, Supply and Construction of Track and Track related Works including Testing and Commissioning for Double Line High-Speed Railway’ in the state

National High-Speed Rail Corporation Limited (NHSRCL), building the bullet train project, is also using various geotechnical instruments including inclinometers, vibration monitors, ground settlement markers, and tilt meters at and around construction sites for monitoring tilt, settlement, vibration, cracks and deformation. (File pic/News18)

It is difficult to accommodate a new infrastructure project in old and congested cities due to land unavailability. Mumbai was no different when planning started for India’s first bullet train project connecting the city with Gujarat’s Ahmedabad. And it was decided that the entire stretch of the high-speed corridor in Mumbai would be underground.

The city will have a 21-km-long tunnel between Bandra Kurla Complex in Mumbai and Shilphata in Thane that will also include India’s first undersea tunnel at Thane Creek. Out of 21 km of tunnelling work, 16 km is through Tunnel Boring Machines (TBM) and the remaining five kilometre is through the New Austrian Tunnelling Method (NATM).

News18 has learnt that as of last week, 1.36 km has been excavated in NATM, while for the remaining part, shafts are ready at three locations.

“For the 16 km TBM part, shafts are ready for lowering TBMs and in the 5 km NATM part, more than a kilometre has been excavated so far,” an official told News18 on condition of anonymity.

The tunnel also includes seven kilometres of India’s first undersea tunnel at Thane Creek.

National High-Speed Rail Corporation Limited (NHSRCL), building the bullet train project, is also using various geotechnical instruments including inclinometers, vibration monitors, ground settlement markers, and tilt meters at and around construction sites for monitoring tilt, settlement, vibration, cracks and deformation.

“These instruments play a crucial role in making sure that neither is there any risk to ongoing underground works like excavation and tunnelling nor to the structures surrounding the site,” they said.

Further, one Additionally Driven Intermediate Tunnel (ADIT) has also been completed for easing the work on the main tunnel. The ADIT was planned to facilitate additional access to the underground/undersea tunnel for faster construction progress The ADIT adds two additional NATM faces for the excavation work in addition to Shilphata.

The 394-metre ADIT tunnel was ready in just six months in May this year. This 11 metre x 6.4 metre ADIT gives direct vehicular access to the main tunnel during construction and operations. It also acts as an evacuation path in case of any emergency.

After slow progress initially, work in Maharashtra for the bullet train project is underway in full swing now. Last month, the NHSRCL invited bids for the “Design, Supply and Construction of Track and Track related Works including Testing and Commissioning for Double Line High-Speed Railway” in the state. Totalling about 157 route km alignment – 314 km of track length – the complete alignment is between the Mumbai bullet train station and Zaroli village at the Maharashtra-Gujarat border. It also includes track works for four stations and a rolling stock depot at Thane.

The tunnel

The main tunnel will be a single tube tunnel to accommodate twin tracks for both up and down tracks. This tunnel will be about 25 to 57 metres deep from the ground level and the deepest construction point will be 114 metres below the Parsik Hill.

A total of three TBMs are planned for the 16 km part. To construct this tunnel of diameter 13.1 m, TBMs with a cutter head of 13.6-metre diameter are being used. These are exceptionally bigger TBMs. For urban metros, TBMs with 5-6 metre diameter cutter heads are used.

The three shafts will be installed at BKC (36m), Vikhroli (56m), and Sawli (39m) at various depths to facilitate the construction. An inclined shaft of 42 metres at Ghansoli and a tunnel portal at Shilphata will facilitate the construction of the remaining 5 km of the tunnel through the NATM method.

Across the tunnel, 39 equipment rooms will also be constructed adjoining the tunnel location as part of the package.

The challenges

For the construction of the tunnel, multiple controlled blasting with sufficient noise and air pollution prevention measures has to be planned to cause minimal disturbance to the environment and population in the adjoining areas.

Also, shafts are constructed in areas with high population density and adjoining utilities like pipelines, electrical installation and other infrastructure projects like metro and highways. The work is also planned in a way to ensure minimal disruption.

The disposal of excavated material is being carried out under the supervision of the Maharashtra Pollution Control Board.

Exit mobile version