Afcons Infrastructure has launched the second of two TBMs to excavate India’s first undersea tunnel as part of the Mumbai–Ahmedabad High-Speed Rail Project.
The TBM was launched from the Sawli (Ghansoli) shaft in Mumbai to excavate towards Vikhroli in Maharashtra. The 10km drive includes a 7km section beneath Thane Creek – the country’s first subsea rail tunnel.
Package C2 is a 21km underground tunnel section between Sawli (Ghansoli) and the Bandra Kurla Complex (BKC) in Mumbai, of which 16km will be constructed by TBM. The first TBM started its 6km drive from Vikhroli towards BKC on July 5.
A 5km section has already been completed using the NATM.
The TBM is among the largest ever deployed for rail tunnel construction in India. The slurry-based mixshield machine has a 13.6m diameter, weighs 3,200 tonnes and is 96m long.
It is equipped with a semi-continuous advance (SCA) system, enabling simultaneous excavation and tunnel segment installation to boost advance rates.
The TBM was launched from a 39m-deep shaft at Sawli. The restricted space required the TBM to be lowered in parts before it was assembled underground.
The trailing back-up system has four double-deck gantries housing slurry pumps, hydraulic equipment, grouting units, electrical systems and emergency refuge chambers.
The TBM is fitted with a real-time gas monitoring system for methane, oxygen, carbon monoxide and carbon dioxide, as well as fire detection and suppression systems.
During excavation, structural performance and groundwater will be monitored by a suite of instruments including settlement markers, tilt meters, strain gauges and seismographs.
To waterproof the tunnels, lining will be protected with double-layer EPDM gaskets combined with hydrophilic seals, ensuring long-term structural durability and safety.
The National High Speed Rail Corporation’s Ltd Mumbai–Ahmedabad High-Speed Rail project is a 508.17km line that will connect Mumbai with Ahmedabad in Gujarat. It will feature 12 stations.
