From February the MMRC will begin tunneling 12.5 km below the mthi river bed as mumbai’s first underground metro the colaba andheri seepz line goes underwater.
The proposed 33.5 km Metro-3 line will be the second metro in the country to have tunnel under a riverbed. The first is being constructed in Kolkata under the Hoogley river.
The MMRC will construct two tunnels of 1.18 km length each with tunnel boring machines , currently used towards Vidyanagari and a 170 m tunnel using the New Austrian Technology method . The tunnels will be between Dharavi and Bandra Kurla Complex. The south end of BKC station will also be underwater.
To accomplish this engineering feat of construction under riverbed the contractors will adopt several safety methods. The soil and broken rocks above the tunnel will be strengthen to reduce permeability and ingress of water. An umbrella of steel bars will be created above the excavation area for safety and there will be a constant check on soil rocks during excavation.
With the water level rising in the river every monsoon , more precaution would be taken to control water pressure . The BKC station is also a crucial intersection point as it is being planned as a three line station with two main platforms and a cross over line , which will connect to either side of the mainline. The crossover line is being constructed using NATM . This will be the first Metro to use NATM under water. The MMRC has completed close to 17km of tunneling in the city with all 17 tunnel boring machines put to work.
The MMRC on Tuesday awarded the contract for automated fare collection system in all of its proposed 27 underground stations to a consortium of M/s. ASIS Elektronik ve Billisim Sistemleri A.S>, Turkey and Kalindee – ASIS joint venture. The AFC system will also follow the integrated ticketing system that is being implemented by MMRDA for seamless travel in the City.