On June 26, TBM S711 – a Herrenknecht Tunnel Boring Machine operated by Afcons Infrastructure made a ‘hidden’ breakthrough at Chennai Metro’s upcoming Sir Theagaraya College Station in north Chennai. After building tunnels for UAA-01, this TBM was commissioned on April 25 2017 from the Washermenpet Station to build the down-line tunnel of Chennai Metro’s 2.4 km UAA-08 project from Washermenpet to Korukkupet as part of a 9.1 km northern extension of the 23.10 km Chennai Airport – Washermenpet line to Wimco Nagar.
Aided by north Chennai’s favorable soil profile which comprises of silty sand, fine sand and clay, the roughly 858 meter journey from Washmermenpet to Sir Theagaraya College took only 2 months to complete.
Excavation is still underway at the Sir Theagaraya College Station, so the TBM isn’t visible. Afcons plans to continue building temporary rings within the station box towards Korukkupet and will later dismantle them during excavation works. A similar ‘hidden’ breakthrough, not visible to workers, was performed by Afcons’ Robbins EPB machine at the Central Station in January 2016 and more recently in Kolkata at Line-2’s Howrah Station.
For images of the TBM shot at Washermenpet, see this post.
The 1st TBM, a Robbins EPB machine, was commissioned in March 2017 to build this section’s parallel up-line tunnel and is currently sitting idle 8.4m (6 rings) away from the station box waiting for its side of the diaphragm wall to get ready.
For more updates, check out the Chennai section of The Metro Rail Guy!