Tunneling work at Mumbai’s underground Metro begins
Residents of old buildings in south Mumbai are worried that the tunneling will affect the structural stability of their houses.mumbai Updated: Nov 11, 2017 00:58 IST
The Mumbai Metro Rail Corporation Limited (MMRCL) has started digging the first tunnel for the 33.5-km underground Metro- 3 line (Colaba- Bandra- Seepz) using a highly mechanised tunnel boring machine (TBM) at Naya Nagar in Mahim on Friday.
Amid protests over how tunneling poses a threat to old and dilapidated buildings, the MMRCL began the gigantic task using a TBM procured from German major Herrenknecht AG’s manufacturing facility in China in September.
By Friday afternoon, the TBM had drilled few millimetres into the ground. An MMRCL official said, “The TBM, which is 110 metre long, will on an average drill 10 m every day. Within 7-10 days, the machine would be completely inside the tunnel.”
The TBM will drive through Shitaladevi Metro Station and will be retrieved at the proposed Dadar Metro station. The machine is expected to cover a distance of 2.5 km in a year.
The TBM being used at the Naya Nagar launching site is one of the 17 TBMs which will be used to construct the 33.5-km-long twin tunnels. Seven launching sites will be created for the Metro-3 line. The entire tunneling is expected to be done in two years. The second TBM at the Naya Nagar site will begin boring next month.
When asked about the difficulties faced in the project, Ashwini Bhide, managing director, MMRCL, said, “As compared to other cities, Mumbai doesn’t have alternate routes and no road can be cordoned off for work. So we have to manage traffic and construction activity.”
The Earth Pressure Balance (EPB) device will be used to construct tunnels in circular cross sections some 20m to 25m below the surface.
While the officials said they have monitored the health of vulnerable buildings, the project has seen few controversies. Residents of south Mumbai have expressed apprehensions over it affecting the structural stability of their buildings. Such tunnels are built in several cities across the world including London. “The tunneling will happen 20m to 25m below the ground and most of the shocks would be absorbed by rocks. There are scientific methods to monitor the health of structures,” added officials.