Page 57 - Trafficinfratech Magazine Aug - Sept

INFRASTRUCTURE

The underwater tunnel below the bed of Hooghly
River connect two iconic Indian Railways stations

– Howrah Junction and Sealdah which is a result
of precise planning and meticulous execution. The
twin tunnels were built in just 67 days while the

budgeted time for tunnelling the 2.9km stretch
was 127 days. Once operational, the service will
revolutionise travel in Kolkata.

nderwater tunnelling has been topmost soil is soft and weak. The settlement
done across the world, and with prone sensitive topography made the team
considerable success. IIndia will face extreme engineering challenges.
soon get its first underwater
Umetro rail tunnel by 2021! Planning
Kolkata Metro- India’s oldest metro rail network, At the outset, suitable designs and
will soon have an European-style underwater technologies had to be selected for a
tunnel as part of its East-West Metro project. successful delivery of the project. The
The project is overseen by Kolkata Metro Rail designing was entrusted to specialised
Corporation Ltd (a government of India entity) world-class design companies such as Atkins,
and executed by Afcons Infrastructure Ltd. Systra and Tunnelconsult. The team chose
Tough task Herrenkeneckht (HK) Tunnel Boring Machines
(TBMs) for this project based on their track
There were several challenges when the record in manufacturing machines which are
work for a project of this magnitude had tailor-made for specific project requirements.
been taken up. Detailed investigations, case HK is also engaged in maintenance of the two
studies, planning, design considerations and
logistic arrangements had to be worked out TBMs deployed for the Kolkata Metro project.
before the tunnel boring machines (TBMs) KMRCL carried out soil investigation work
could plunge below the river. Tunnelling, at the pre-tender stage for feasibility study.
be it underground or underwater it is very In addition to this, Afcons also carried out
challenging due to the risk of water ingress extensive soil investigation work for the
and impact of topography. The bore has to entire tunnel alignment, deploying floating
be dug deeper due to possibility of water barges and pontoons in the river portion. The
inflow which requires high level of detailing company also conducted extensive condition
and preparation. survey of the buildings in proximity before
However, it is the alignment of the project carrying out tunnelling to ensure there were
which pass through a precarious topography no untoward surprises during tunnelling as
necessitating tunnel in the vicinity. The geology well as to map out the safest layer below the
of Kolkata and Howrah is erratic, especially the riverbed for tunnelling.

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