TBM S703 Makes a Breakthrough at Chennai Metro’s AG-DMS Station

With some external assistance, TBM S703 – a Herrenknecht tunnel boring machine operated by Afcons Infrastructure on October 18 made its final breakthrough at Chennai Metro’s AG-DMS Station after a 55 month long and tiring journey to build the 4.5 km down-line tunnel on package UAA-02 of the 32.10 km Line-1 between Chennai Airport and Wimco Nagar.

The breakthrough event with more than 300 attendees was originally planned to take place on the 17th, but the TBM just wasn’t able to penetrate through the 1 meter thick diaphragm wall due to its worn out disc cutters. The tunneling team then deployed a drilling excavator overnight and had the TBM finish up the job in the morning.

The earth pressure balance machine (EPBM) was originally commissioned by the Gammon – Mosmetrostroy JV from the May Day Park Shaft in March 2013, and made successful breakthroughs at Government Estate Station in October 2013 & LIC Station in May 2014 before being abandoned in May 2015 due to financial issues. After conducting two rounds of bidding, the Chennai Metro Rail Corporation in May 2016 awarded Afcons Infrastructure with a contract to complete the balance tunneling work towards Thousand Lights Station and onward to AG-DMS Station.

Tunneling works resumed in July 2016 with the TBM soon entering the Thousand Light Station’s box in August where its damaged cutterhead was refurbished via a small shaft. Tunneling towards AG-DMS resumed in November during which the team initially made great progress, with excavation rates as high as 32m/day, but soon encountered difficult conditions with loose top soil that led to a cave-in on Anna Salai.

In total, the TBM built 2619 rings (1 ring on this package is 1.5m long & 1.4m on curves) throughout its journey of which 1360 were built by Afcons Infrastructure.

UAA-02 section (May Day Park Shaft – AG-DMS) of Chennai Metro – view Chennai Metro map & info

View on the 17th while waiting for the TBM to show its pretty face – Photo Copyright: CMRL

Drilling excavator deployed on the the night of the 17th – Photo Copyright: Ankit Lowanshi

Breakthrough! – Photo Copyright: H Jurgen Mick

Photo Copyright: Ankit Lowanshi

Diaphragm wall with the TBM’s cutterhead – Photo Copyright: Ankit Lowanshi


Meanwhile, TBM S704 on the parallel up-line tunnel has another 300 rings pending to reach AG-DMS Station while the Robbins TBM 219-364 on package UAA-08 has another 152 rings pending to reach Korrukupet Station to wrap up all tunneling works on the 54.1 km Phase 1 & Phase 1 extension projects.

For more updates, check out the Chennai section of The Metro Rail Guy!


written by

Global traveler who prefers mass rapid transit

20 Responses to "TBM S703 Makes a Breakthrough at Chennai Metro’s AG-DMS Station"

  1. Anand Meher says:

    Congrats to entire AFCONS team. Now focus has moved to next breakthrough.

  2. Madhu says:

    What is ur estimate for complete Phase1 to get operational? TN Govt. predicts by Mid of next year.

  3. Muthu says:

    Do you have a single place where the dates of all breakthroughs can be found?

    • TMRG says:

      Nope. For breakthroughs that took place prior to starting this site, I have to go on a wild goose chase to get dates from contractors and online sources, and then verify with other sources.

      If you’re looking for recent breakthroughs, try searching for ‘breakthrough’ in the search box. That should bring up all posts in a chronological order.

  4. Shreeharsha Phene says:

    Mr TMRG,

    The total time taken for this 4.5 Kms tunnel of 55 months is a average speed of ~2.7 mts ie lessthan
    Two tunnel rings a day.From the repot it is clear that the delay in the project execution is on three accounts:
    1Financial difficulty and therefore failure of Gammon.
    2 Delay in awarding the second contract ( almost 16 months).
    3The Delay for Afcons contract on account of type of soil.

    In Mumbai Metro MMRC is considering tunnelling speed of 10 Mts a day I.e average 6 tunnel rings a day,do you think this is reasonable?

    Your expert comments please.

    S V Phene

    • TMRG says:

      I’m not an expert. Quite far from it actually, but believe the tunneling estimates of Mumbai are highly optimistic and based on the best case scenario as if things will work like clockwork.

      Even the best of experts cannot predict how the machines will perform, how the entire tunneling path looks like or what lies ahead when things get moving. It’s good to be optimistic, but even MMRCL’s team deep inside knows that 1 TBM drive going awry can (and will) derail the entire project.

    • Akhilesh shukla says:

      Time cycle consider from past experience only. For NATM they consider less productivity in mumbai. 10 m is productivity for EPBM…

  5. Gaurav says:

    What are they going to do with the TBM now?

    • TMRG says:

      Plan is to retrieve, dismantle and hand over both S703 & S704 to the Chennai Metro Rail Ltd.

      Gammon-MosMetrostroy still owns them, but the CMRL will return them only after the legal issues are sorted out.

  6. USOZ says:

    Any idea when the TN Govt will merge the Chennai Mass Rapid Transit System with the Metro Rail into a single entity? I know its been discussed numerous times.

    • TMRG says:

      PwC’s report on the merger is supposed to be out soon. That’ll dictate the changes required, but timing wise it’s all up to the TN govt, Indian Railways and funding. Whenever initiated, I see the merger taking place over a period of 2-3 years; it can’t happen overnight.

  7. kumaran says:

    Hi TMRG, you saying phase 1 Extn ‘ll open 2021, but cmrl says 2019 – early 2020???

    • TMRG says:

      Work on the elevated section commenced this summer. It needs at least 3-4 years to get ready. 3 key contracts for the line’s piers/stations and Wimco Nagar Depot are yet to be awarded.


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