The Delhi Metro Rail Corporation (DMRC) on 2 June, started a tunneling drive by the Tunnel Boring Machine (TBM) named “Bhoomi” from Derawal Nagar to Pulbangash, on the Magenta Line extension (Line-8).
This line extends from Janakpuri West to R K Ashram corridor. The length of the tunnel between Derawal Nagar and Pulbangash is approximately 3 km.
The depth of tunneling will vary from 12.4 m at Derawal Nagar station and upto 25.9 m near the Najafgarh drain. Therefore, the TBM will traverse through varying geological levels underground.
In a first of its kind exercise, Delhi Metro is equipping all its TBMs with the Bore Tunneling Electrical Ahead Monitoring (BEAM) System in this phase.
It enables the TBM to predict on a real time basis the geological strata upto 20 m ahead of the machine’s cutter head face and predict any unexpected encounter with filled wells, cavities, and aquifers which may lead to settlement over the ground if hit by the TBM without proper treatment.
BEAM is a non-intrusive focused-electrical induced, polarisation ground predicting technique, especially designed for the underground construction industry.
It can be used in any hardrock, soft and mixed ground geology, under or below the ground water table and thus in any type of boring machine like EPB, Slurry, Gripper, Single or Double shielded TBMs, independent from the TBM manufacturer.
The tunnel shall pass below many residential and commercial areas on GT Karnal Road like Derawal Nagar, Rana Pratap Bagh, Shakti Nagar, Kamla Nagar, Ghanta Ghar, Subzi Mandi, Roshanara Road etc.
At present, four TBMs are operational across the city in the three priority corridors (Janakpuri West-RK Ashram Marg, Majlis Park-Maujpur and Tughlakabad-Aerocity) under Phase IV.a
A total of 28 kilometres of new underground corridors are being constructed as part of this phase.
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