Delhi Metro Update: DMRC completes first TBM tunneling works on Janakpuri West-R.K Ashram Marg corridor of Phase-4 project

A major milestone in DMRC’s Phase 4 construction work was achieved today as the first ever tunnelling stretch of Phase 4 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 main tunnelling work on this stretch was commenced in April earlier this year after completing the initial drive. 
• Despite the many constraints posed by the Covid-19 pandemic, work was continued and this major milestone could be achieved. 
• This tunnel breakthrough using a mammoth 73 metre long TBM was achieved today in the presence of DMRC’s Managing Director, Dr. Mangu Singh and other senior officials.

• Two parallel circular tunnels for up and down movement are being constructed on this stretch which is a part of the 2.2 kilometre long underground section from Janakpuri West to Keshopur. 
• Tunneling work on the other parallel tunnel shall commence soon.
• This new tunnel is a continuation of the earlier Magenta line tunnel that was already constructed for the presently operational Botanical Garden – Janakpuri West corridor. 
• The tunnel has been constructed approximately at a depth of 14 to 16 metres. 
• Over a thousand rings have been installed in the tunnel. 
• It has an inner diameter of 5.8 metres. 
• The alignment of the tunnel runs along the Outer ring road and below the multi-storied built up structures.
• The tunnel has been built with the proven technology of EPBM (Earth pressure balancing method) with concrete lining made up of precast tunnel rings. 
• The tunnel rings have been cast at the fully mechanized casting yard setup at Mundka. 

About the Project:

• These concrete segments were cured with a steam curing system to achieve early strength.
• All necessary safety precautions were taken while constructing the tunnel below the built up structures by monitoring the ground movements with highly sensitive instruments fixed on the nearby structures. 
• As part of the Phase 4 work approved so far, about 27 kilometres of underground lines will be constructed. 
• The Janakpuri West – RK Ashram Marg corridor will have underground sections of 7.74 kilometres in total.
• A TBM is a machine used to excavate tunnels with a circular cross section through a variety of soil and rock strata. 
• They can be designed to bore through anything from hard rock to sand. 
• TBMs have revolutionised the way tunnelling work is done all over the world as now tunnels can be bored without disturbing the buildings and other structures on the surface.
• TBMs are especially useful for underground tunnelling work in congested urban areas. 
• DMRC has been using TBMs for its tunnelling work since Phase 1. 
• In Phase 3, when about 50 kilometres of underground sections were built, about 30 TBMs were pressed into service in the national capital.

Source: DMRC-Press Release