The bullet
train, the big-ticket headline-grabbing project now firmly under way, includes
an engineering marvel: the country’s first undersea rail tunnel. It will come
up just north of Mumbai, near Thane Creek.
The National
High Speed Rail Corporation Limited (NHSRC), the implementing agency for the
Mumbai-Ahmedabad high speed rail corridor, completed ‘static refraction
testing’ for the undersea tunnel on December 24. The test involved firing
high-energy sound waves towards the seabed from below the surface of the water
and mapping the resultant refracted sound waves to determine the density of the
rock under the seabed.
To ascertain
soil strength, exploration for undersea tunnel was carried out 70 metres below
ground level. As many as 66 bore holes with a gap of 250 metres between each
pair have been drilled in a staggered fashion (that is, alternating diagonally)
on its alignment with Japanese jack-up well equipment. Soil strength has turned
out to be good and now construction will be carried out 40-45 metres below the
seabed.
“Only a very
dense rock can safely support a tunnel of the present nature. The study has now
been taken to Tokyo. After its analysis by Kawasaki Geological Engineering Co
and Indian Geotechnical Services the findings will be available by second week
of January. Thereafter, Japan International Consortium for Transportation Co.
Ltd. (JIC) will do the designing of the underground corridor,” says UP Singh,
chief project manager, NHSRC.
Seven km out of
the 21 km of the twin-track underground tunnel will pass under the seabed,
mangroves and marshlands on either side of the creek. A stretch of 1.8 km of
these seven kilometres will be constructed under the seabed. NHSRC and RITES, a
railway ministry organisation, have also completed the survey of mangroves
around the creek using the light detection and ranging (LIDAR) scanner, a data
recorder and other equipment with a 100 megapixel camera. This aerial-survey
method provides accurate data about land contours, buildings and vegetation.
The project
corridor will begin at the underground station in the Bandra-Kurla Complex
(BKC) in Mumbai and then traverse 21 km underground within seven-eight minutes
before emerging above ground near Shilphata Diva Naka. It will end at the
Sabarmati station in Ahmedabad.
According to
NHSRC, a 100-member design team is working on tweaking the engineering of
Japan’s Shinkansen technology to make it work in Indian conditions.
The prime
minister’s office (PMO) has sought weekly updates on the progress of the
project, and engineers are working round the clock to ensure that prime
minister Narendra Modi’s ambitious project is implemented on time, says Singh.
Plans are being
prepared by JIC and construction is expected to start in the third quarter of
2018 with tunnelling work, execution of stations and construction of bridges.
Three tunnel-boring machines will be deployed. Ventilation shafts will be put up
at every 7.5 km of the tunnel to give an outlet for fumes emitted by the bullet
train. The shafts will also be used for transporting out debris and muck
generated due to digging which will be recycled by environmental consultants.
“With the 21-km
tunnel going underground, problems of relocation will not arise, but old
buildings en route will have to be strengthened,” adds Singh.
Meanwhile,
relocation of utilities is going on and NHSRC is setting up a High Speed
Railway Training Institute in Vadodara. The institute will provide training for
systems and maintenance operations to the personnel, beginning with 4,000 staff
members.
The Rs 1,10,000
crore project is expected to be a reality by August 15, 2022 – the 75th
Independence Day. The underground tunnel construction is estimated to cost Rs
3,500 crore.
http://www.governancenow.com/news/regular-story/work-begins-on-indias-first-undersea-rail-tunnel
