Construction for first undersea rail tunnel for bullet train starts

25 Jul 2024 CW Team

The work is advancing towards the Thane Creek, where a portion of the tunnel will pass beneath the creek, making it India's first undersea rail tunnel. NHSRCL engineers have constructed a unique 'T intersection' from the Additionally Driven Intermediate Tunnel (ADIT) at Ghansoli in Navi Mumbai, connecting it to the main tunnel. At 110 meters, this is the deepest point of the 21-km-long tunnel.

Nestled amidst dense tree cover, the ADIT acts as an entry/exit point perpendicular to the main tunnel. One section goes towards BKC (below Thane Creek), while the other heads towards Shilphata in Thane. Within a month, 120 meters towards BKC and 110 meters on the Shilphata end have been excavated, involving 218 blasts using gelatin explosives. A total of 314 blasts have been carried out for the ADIT.

"The tunnel will be almost 25-30 meters deep into the earth's crust from the bottom of Thane Creek," said an NHSRCL engineer. "We are using the New Austrian Tunnelling Method (NATM) carefully due to nearby buildings and structures. Despite heavy rains, our work continues."

NHSRCL is carving a single-tube rail tunnel for the Up and Down lines. Engineers carry out an average of four explosions a day, drilling 180 to 200 two-meter-deep holes using specialized equipment from Japan.

Two massive motor-powered rubber tubes force fresh air into the main tunnel through the ADIT, helping the 150-odd workers on site working in two shifts. "Every time we undertake detonation work, we deflate the rubber tubes, switch off the high-powered lights, and make our men stand outside. After the explosions, we defume the tunnel by pumping in fresh air," said another engineer.

After blasts, workers inspect the tunnel for loose rocks or chances of collapse. The sturdy rocks dent barely three to four meters with each blast. JCBs remove fallen rocks, followed by dump trucks carrying muck and rock to the designated dumping ground at Turbhe. The semi-tunnel is then strengthened using specialized cement, steel bolts, and other elements. Monitoring instruments gauge changes in soil, seismic activity, and overall tunnel health, providing real-time updates directly connected to a server.

The work is expected to be completed by December this year, around the same time when three large tunnel-boring machines (TBMs) will arrive at Ghansoli, Vikhroli, and BKC to take over the tunneling work. The first TBM is likely to enter from Ghansoli before Thane Creek, where NATM works end and will help go beneath the creek.

Progress on the bullet train in Gujarat is faster than in Maharashtra. The 352-km section through Gujarat is expected to fully open in 2027, with the 50-km stretch from Surat to Bilimora opening in August 2026. The remaining section to Mumbai is expected to open by the end of 2028.

(Source: HT)

As Indian Railways tackles back-to-back derailments, significant progress is being made on the country's first high-speed rail corridor connecting Mumbai with Ahmedabad. The National High Speed Rail Corporation Limited (NHSRCL) is excavating for the only underground bullet train station at Bandra Kurla Complex (BKC) and the first dual rail line underground tunnel for the Rs 108 trillion rail project. The work is advancing towards the Thane Creek, where a portion of the tunnel will pass beneath the creek, making it India's first undersea rail tunnel. NHSRCL engineers have constructed a unique 'T intersection' from the Additionally Driven Intermediate Tunnel (ADIT) at Ghansoli in Navi Mumbai, connecting it to the main tunnel. At 110 meters, this is the deepest point of the 21-km-long tunnel. Nestled amidst dense tree cover, the ADIT acts as an entry/exit point perpendicular to the main tunnel. One section goes towards BKC (below Thane Creek), while the other heads towards Shilphata in Thane. Within a month, 120 meters towards BKC and 110 meters on the Shilphata end have been excavated, involving 218 blasts using gelatin explosives. A total of 314 blasts have been carried out for the ADIT. The tunnel will be almost 25-30 meters deep into the earth's crust from the bottom of Thane Creek, said an NHSRCL engineer. We are using the New Austrian Tunnelling Method (NATM) carefully due to nearby buildings and structures. Despite heavy rains, our work continues. NHSRCL is carving a single-tube rail tunnel for the Up and Down lines. Engineers carry out an average of four explosions a day, drilling 180 to 200 two-meter-deep holes using specialized equipment from Japan. Two massive motor-powered rubber tubes force fresh air into the main tunnel through the ADIT, helping the 150-odd workers on site working in two shifts. Every time we undertake detonation work, we deflate the rubber tubes, switch off the high-powered lights, and make our men stand outside. After the explosions, we defume the tunnel by pumping in fresh air, said another engineer. After blasts, workers inspect the tunnel for loose rocks or chances of collapse. The sturdy rocks dent barely three to four meters with each blast. JCBs remove fallen rocks, followed by dump trucks carrying muck and rock to the designated dumping ground at Turbhe. The semi-tunnel is then strengthened using specialized cement, steel bolts, and other elements. Monitoring instruments gauge changes in soil, seismic activity, and overall tunnel health, providing real-time updates directly connected to a server. The work is expected to be completed by December this year, around the same time when three large tunnel-boring machines (TBMs) will arrive at Ghansoli, Vikhroli, and BKC to take over the tunneling work. The first TBM is likely to enter from Ghansoli before Thane Creek, where NATM works end and will help go beneath the creek. Progress on the bullet train in Gujarat is faster than in Maharashtra. The 352-km section through Gujarat is expected to fully open in 2027, with the 50-km stretch from Surat to Bilimora opening in August 2026. The remaining section to Mumbai is expected to open by the end of 2028. (Source: HT)

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