CMRL is currently constructing the underground section of corridor 4, which comprises two portions, UG1 and UG2, each containing four km of twin tunnels.
To complete the 16 km of upline and downline tunnels, four tunnel boring machines have been planned to be used. ITD Cementation India Limited, the contractor, has procured these machines from The German company, Herrenknecht.
Recently, the first factory Acceptance test of the first tunnel boring machine was conducted at the HK factory in Ponnery in the presence of CMRL project director T Archunan. This TBM, known as S1073B, has a bore diameter of 6.670 metres and an earth pressure balance of 110 metres. The weight of the massive machine is approximately 700 tonnes, which will be dismantled for transportation and placed at the destination, Light House station.
Construction for a launch shaft to house the Tunnel Boring Machine (TBM) is currently in progress at Light House station and is projected to be complete by May.
This TBM will be sent down Corridor 4 and travel up to 29 metres below ground, starting from Light House, Kutchery Road, Tirumaylal, Alwarpet, Bharatidasan, until it reaches Boat Club by May 2025.
The second stage of the Metro Rail project, spanning 118.9 km and consisting of 128 stations, is currently underway.