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