By rosebell
As the first TBM breakthrough for the UG-01 contract, the upline TBM, Eagle, has broken through at Thirumayilai on Corridor 4, whereas on Corridor 3, the downline TBM, Noyyal, arrived at the Mandaveli shaft on 7 February.
Launching TBMs Noyyal and Vaigai, excavation between Greenways Station and Mandaveli Station on Corridor 3 was commenced in September 2023, and the TBM Vaigai achieved its breakthrough on the upline in October last year.
The latest breakthrough is the eighth on the TU-02 contract.
With 763m length, this tunnel is executed by Larsen & Toubro Ltd and passes beneath densely built-up areas, with an overburden ranging from 9-12m and main underground utilities in the Mandaveli shaft area posed additional challenges.
Due to facing predominantly silty sand and sandy soil conditions the TBMs were operated mainly in closed-face mode. Completing the drive in 449 days, excluding the waiting period near the shaft for completion of shaft construction, a total of 14 cutterhead interventions were carried out on TBM Noyyal.
Including almost 4km of twin tunnels, the underground section of Corridor 4 from Light House Station to Kodambakkam Flyover has been divided into two packages, UG-01 and UG-02. With the aim of implementing around 16km of tunneling in both directions, four 6.67m-diameter TBMs have been deployed.
Following commissioning TBMs Eagle and Flamingo in January 2024 tunneling between Light House Station and Thirumayilai Station commenced.
With an overburden depths ranging from 4.5-23m, 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, as well as 151 buildings.
Considering that 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 tunneling was completed over a period of 24 months.
Stretching from Panagal Park to Boat Club Station under Corridor 4, UG-02, TBM Pelican has started its final drive, whereas this machine had earlier completed a 2km drive from Panagal Park to Meenakshi College, safely passing beneath active Indian Railways tracks.
Being launched earlier on the same section, TBM Peacock 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.
