A little more than four years after being commissioned from Washermenpet in north Chennai, Tunnel Boring Machine S710 finally made its 3rd and final breakthrough for Chennai Metro’s package UAA-01 on Friday afternoon at the Central Station. The Herrenknecht EPB TBM, operated by the Afcons-Transtonnelstroy JV, was last commissioned from the High Court Station in August 2014 (after a breakthrough there in March) and traveled roughly 1.3 km while building 928 rings along the way for the 32.10 km Wimco Nagar – Airport line.
This TBM, like its sister machine TBM S711, encountered mixed face hard rock conditions as they passed in the vicinity of several historic buildings with weak foundations. As such, tunneling had come to a stand-still in early 2016 and it became impossible to operate both TBMs at the same time. In July 2016, TBM S710 restarted mining after S711 was far ahead and out of its influence zone.
This breakthrough marks the completion of tunneling works on package UAA-01 (Egmore & May Day Park – Washermenpet), was the 6th to be recorded at the Central Station and overall the 38th of 40 breakthroughs in Chennai. The first breakthrough at Central was achieved in July 2014, 2nd in January 2016, 3rd in October 2016, 4th in November 2016 and 5th in December 2016.
There are now just 2 more TBM breakthroughs left on package UAA-02 (May Day Park – AG-DMS; shown in green in the map at the top of this post) for all tunneling works to end on Chennai Metro’s 45.1 km Phase 1 project. Here’s their progress as of February 10 (each ring = 1.4m)
For more updates, check out the Chennai section of The Metro Rail Guy!