Two Tunnel Boring Machines (TBMs) that would be used to build the underground section of Metro Rail have arrived from China. The process of transporting the machines, which were shipped to the Chennai port as five to six separate segments, to the launch sites has commenced.
In due course, nine more machines would arrive in the city and all 11 TBMs would be deployed simultaneously to build the 24-km underground section of the Metro Rail network over the next three years.
To minimise the impact on traffic, the components are being transported at night. Shenoy Nagar Park, which is one of the five TBM launch sites, received its first consignment on Friday.
Chennai Metro Rail Limited Managing Director K. Rajaraman said work on building the launch shafts (through which the TBM would be eased to a depth of nine metre beneath the ground) is on in many locations. “Apart from Shenoy Nagar and Washermenpet, such shafts would be built in May Day Park in Chintadripet, Nehru Park in Poonamallee High Road and Saidapet. The component assembling and operational trial of the TBMs would go on simultaneously,” he said.
Full-fledged underground tunnelling is expected to begin around mid-February, he added.
30-storey tall
Each TBM weighs around 140 tonnes. The entire assembly stretches to a length of nearly 90 metre. When placed vertically, it would be as tall as a 30-storey building.
TBMs are specially designed machinery used to build tunnels with a circular cross-section. They are deployed especially in urban settings where ground excavations can lead to large-scale disruptions.
Each TBM has one or two large metal cylinders (shields) mounted on a trailing support mechanism. The front of the shield has a rotating cutting wheel, which will do the tunnelling.
The Chennai Metro Rail project has two corridors – Washermenpet to Airport and Chennai Central to St.Thomas Mount. A portion of the Metro alignment on Corridor-I, between Washermenpet – Saidapet ramp, and on Corridor-II, between Central and Thirumangalam ramp, runs as underground tunnels. Of the 36 upcoming Metro stations, 20 would be underground.
