Two slurry-based tunnel boring machines (TBM), Helen and Maragarita, are at work, involved in the construction of the East-West corridor of Namma Metro in Bangalore. Photo : Bhagya Prakash K.
The TBMs are 95 metres long and weigh about 280 tonnes each. The highest they have burrowed per minute in Bangalore is 24 mm. Photo: K. Murali Kumar
The tunnels are being burrowed anywhere between 11 m and 18 m below the ground. The inner diameter of the tunnels is 5.6 m. Photo: K. Murali Kumar
Theodolite, a survey instrument with a self-rotating telescope, is used to gauge the path of the TBMs. The instrument is fixed on the rear of a TBM. Photo: Bhagya Prakash K.
The survey instrument is read from the control room, positioned behind the TBM. Any deviation from the path is corrected using the touch-screen controls. Photo: Bhagya Prakash K.
Changing of discs of the cutter head of the TBM is a skilful job that only the Thai workers undertake, as it requires acclimatisation in the pressure chamber. Photo: K. Murali Kumar
Sixty people from Thailand have been working on the East-West underground section of the Namma Metro, often communicating in sign language with workers from India. Photo: K. Murali Kumar
The underground work, in the elevated temperature inside the tunnel, takes a toll on the body. Photo: K. Murali Kumar
While the tunnelling work between Majestic and Central College has been completed, the TBM is likely to reach the Vidhana Soudha site by October-end. Photo: K. Murali Kumar