Page 58 - Trafficinfratech Magazine Aug - Sept

INFRASTRUCTURE

Innovations under high hyperbaric pressures river.
The tunnelling alignment was such
Afcons engineers improved upon
numerous processes while planning that it passed through several heritage
structures like Howrah Rail Yard,
The Project the project. Due to site constraints, the which is one of the busiest rail yards
TBMs had to be driven through Howrah
incorporated the station in advance. This was a delicate in the country with over 670 trains
running daily and a footfall of over 10
world’s latest and operation, where they encountered lakh. Boring below these structures
difficulties in crossing the diaphragm
best practices walls. Afcons designed a ‘soft eye’ of was precarious, and tunnelling was
in design and styrofoam replacing M-40 concrete, done more than 350m below the
yard for each tunnel. The TBMs had
which worked extremely well for this
implementation project. This is a first design-of-its kind to negotiate a sharp curve of radius
processes thereby attempted in India by in-house design 228m, plunging into clay surface
and then pass by the piers of Bankim
engineers. Certain criteria in the
saving in time, segmental lining were adapted and Setu. One more curve of 226m radius
cost and space. additional operational precautions and was achieved near Rajbhavan before
checks were implemented to prevent Esplanade station. There are very few
any untoward incidents. examples of such tight curves being
undertaken in Metro tunnelling in
Execution the country. Despite the constraints,
A team of highly experienced tunnel the tunnelling activity began as per
experts was deployed, should an entry schedule, with the two TBMs covering
into the cutting chamber be required roughly 11 to 12 metres in a day.

58 August-September ’19 / TrafficInfraTech www.trafficinfratech-com-500653.hostingersite.com