Tunnelling work for Phase II of Namma Metro is expected to start in February. The vertical shaft at Shivajinagar is being made ready to accommodate two tunnel boring machines (TBMs).
The two machines will start their journey from Shivajinagar and move towards Vellara Junction.
B.L. Yashwanth Chavan, Chief PRO of BMRCL, said, “The machines have already been dispatched from China and are likely to reach Chennai by the first week of February. Then they will be transported to Bengaluru.”
They will then be assembled at Shivajinagar. “The contractor, who bagged the tender, is procuring the machines as per the specifications of the project. Each machine may cost up to ₹75 crore,” he added.
The two TBMs will build a tunnel network of 2.76 km between Vellara Junction and Shivajinagar. The contractor will be deploying an additional two machines to tunnel a stretch of 2.884 km from Shivajinagar metro station to Tannery Road metro station.
These machines are expected to arrive from China later.
The official said, “Going by our experience of Phase I and geo-technical studies of the alignment, a TBM can tunnel up to 5 metres a day. However, this will depend on the geological conditions.”
During Phase I, the TBMs faced hard rocks due to which the project was delayed by many years.
The BMRCL had taken more than four years to complete the entire underground tunnel network of 8.8 km.
According to officials, when it encounters hard rock, the machine can drill up to only three metres per day instead of a stretch of up to 11 metres of soil.
The BMRCL has estimated that it would take 30 months to complete the tunnel work between Vellara Junction and Pottery Town.
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