CHENNAI: It was a historic moment for Chennai Metro rail as the concrete slab which stood between the ramp linking Koyambedu with Thirumangalam was brought down by the giant tunnel boring machine amidst the cry of joy of metro rail workers.
The 5km of two passage of tunnels were well lit and symbolized the tireless efforts of unsung metro rail workers who worked for nearly two years to finish the five kilometer stretch.
“The tunnel work is being carried out on five different packages and this is the fifth package and the first one to be completed,” said V K Singh, chief general manager of Chennai Metro Rail (Underground Construction) V K Singh said that it took nearly two years to finish the work.
“The work on this package started on December 2012 and we were able to drill 15 metre to 18 metre despite facing challenges of uneven surface.
“It was either clay or rocky surface and the biggest satisfaction was that the whole work went on smoothly,” he said. Director of projects, Chennai Metro Rail, R Ramanathan said that after the tunnel, there will be a phase of transition as it will be linked to a box and from there to the ramp with an elevation of 60 metres before reaching Koyambedu station.
Interestingly, 70 per cent work on the stations in the stretch --- Shenoy Nagar, Anna Nagar East, Anna Nagar Tower and Thirumangalam is completed. The tunnels are designed with a walking space with cross passage at every 250 metres.
The biggest challenge was to ship out the mud from the site. As the tunnel boring machine dug out the clay it was transported through a chamber to a small train which would take it all the way to Shenoy Nagar. “From Shenoy Nagar, it will be taken out by a truck between 12am to 6am and dumped at Tiruneermalai,” said V K Singh.
Interestingly, work on the Thirumangalam station concourse was progressing smoothly. The station has two fire exits besides two access points for firemen. It is built 16 metre below the surface and the passenger has to travel further eight metre below to catch his train. Interestingly, Chennai Metro Rail would be the only one of its kind to have the underground stretch platform covered with doors. “They would open once the train arrives.
Delhi metro has this facility only at the airport stretch. No other metro has such a kind of facility,” said R Ramanathan, director of Projects, Chennai Metro rail Limited. Interestingly, the ventilation fans in the stations are the only hope for passengers travelling underground. They work on three different systems. “It will be dependent on power from Tamil Nadu electricity Board besides having a back-up from generator and also UPS,” said Singh.
In case of a natural catastrophe where the power utilities fail, the UPS gives a time of two hours. “This gives enough time for the passengers to reach out safely,” he said. In case of smoke, we will run the system in such a way that the smoke is taken in through one passage.
“It is like blow-in and blow-out,” he said. The stations will have lifts and escalators besides a ticket counter. The station will also have a control room besides being monitored from Koyambedu.