On Corridor 3, the downline TBM, Noyyal, arrived at the Mandaveli shaft on Saturday, while on Corridor 4, the upline TBM, Eagle, has broken through at Thirumayilai, marking the first TBM breakthrough for the UG-01 contract.
On Corridor 3, tunnelling between Greenways Station and Mandaveli Station started in September 2023, with the launch of TBMs Noyyal and Vaigai. TBM Vaigai achieved its breakthrough on the upline in October last year.
The latest breakthrough is the eighth on the TU-02 contract.
The tunnel, executed by Larsen & Toubro Ltd, is 763m long and passes beneath densely built-up areas, with an overburden ranging from 9-12m. Major underground utilities in the Mandaveli shaft area posed additional challenges.
The TBMs encountered predominantly silty sand and sandy soil conditions and were operated mainly in closed-face mode. A total of 14 cutterhead interventions were carried out on TBM Noyyal. The tunnel drive was completed in 449 days, excluding the waiting period near the shaft for completion of shaft construction.
The underground section of Corridor 4 from Light House Station to Kodambakkam Flyover has been divided into two packages – UG-01 and UG-02 – each comprising approximately 4km of twin tunnels. Four 6.67m-diameter TBMs have been deployed to execute nearly 16km of tunnelling in both directions.
Tunnelling between Light House Station and Thirumayilai Station commenced in January 2024 with the launch of TBMs Eagle and Flamingo.
TBM Eagle’s 1.98km-long drive, executed by Cemindia Projects Ltd – formerly ITD Cementation India Ltd – passes beneath several historic and sensitive structures, including Chennai Lighthouse, All India Radio, the Russian Embassy, a church and schools. The alignment passes under 151 buildings, with overburden depths ranging from 4.5-23m.
The tunnel drive encountered challenging geological conditions, including rock strata and gas leakage, particularly near St Raphael’s School.
The TBM operated mainly in closed-face mode, with 17 cutterhead interventions, and tunnelling was completed over a period of 24 months.
Meanwhile, TBM Pelican has started its final drive, tunnelling from Panagal Park to Boat Club Station under Corridor 4, UG-02. The TBM had earlier completed a 2km drive from Panagal Park to Meenakshi College, safely passing beneath active Indian Railways tracks.
TBM Peacock, launched earlier on the same section, has already completed 370m of a 1.898km drive.
CMRL’s Phase 2 Metro Rail Project across Chennai city, covers 118.9km across three corridors with 128 metro stations.
