Yesterday, TBM 219-364 – a Robbins Tunnel Boring Machine operated by Afcons Infrastructure made a 2nd ‘hidden’ breakthrough at Chennai Metro’s upcoming Sir Theagaraya College Station. After building both tunnels of package UAA-01 between the May Day Park shaft and Central Station, this Earth Pressure Balance TBM was commissioned on March 27, 2017 from the Washermenpet Station to build the up-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.
The Robbins TBM’s 863 meter journey to Sir Theagaraya College was aided by north Chennai’s favorable soil profile which comprises of silty sand, fine sand and clay, and took a little more than 3 months. Part of this time frame includes down-time 8.4m (6 rings) behind the station’s diaphragm wall waiting for it to be completed.
To rehash from the post on TBM S711 which arrived here in late-June, excavation is still underway at the Sir Theagaraya College Station, so this TBM isn’t visible either. 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 the same 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.
Meanwhile, Afcons Infra continues to make good progress on package UAA-02’s tunnels (May Day Park – AG-DMS) since July 2016 when it picked up pending work abandoned by the Gammon-Mosmetrostroy JV in May 2015. Here’s the progress made by the two Herrenknecht EPB TBMs as of July 11 (1 ring = 1.4m) –
For more updates, check out the Chennai section of The Metro Rail Guy!