The tunnel breakthrough using a 73 metre long TBM was done on December 31The first-ever tunnelling stretch of Delhi Metro's 4th phase was completed at Krishna Park Extension on the Janakpuri West - RK Ashram Marg corridor with a tunnel boring machine (TBM) breaking through after boring a 1.4 kilometre long tunnel.
The primary tunnelling deal with this stretch began in April last year after finishing the preliminary drive.
The tunnel breakthrough using a 73 metre long TBM was done on Friday, according to information shared by metro operator Delhi City Rail Corporation (DMRC).
Two parallel circular tunnels for up and down motion are being built on this stretch which is a part of the 2.2 kilometre long underground section from Janakpuri West to Keshopur.
The new tunnel is a continuation of the earlier Magenta line tunnel that was currently built for the currently operational Arboretum - Janakpuri West corridor.The tunnel has actually been constructed around at a depth of 14 to 16 metres.
Over a thousand rings have been installed in the tunnel.
It has an inner size of 5.8 metres.
The positioning of the tunnel runs along the Outer ring roadway and below the multi-storied built-up structures.The tunnel has been built with the innovation of EPBM (Earth pressure balancing method) with concrete lining comprised of precast tunnel rings.
The tunnel rings have been cast at the fully mechanized casting lawn setup at Mundka.
These concrete segments were cured with steam treating system to attain early strength, according to DMRC.As part of the Delhi City network's Phase IV work authorized so far, about 27 kilometres of underground lines will be constructed.
The Janakpuri West - RK Ashram Marg corridor will have underground areas spread across 7.74 kilometres in total.A tunnel dull machine is used to excavate tunnels with a circular sample through a variety of soil and rock strata.
They can be developed to bore through anything from acid rock to sand.
These devices have revolutionised the way tunnelling work is done all over the world as now tunnels can be tired without disturbing the structures and other structures on the surface area.