A major milestone in DMRC’s Phase 4 work was achieved today as the first tunnel boring machine (TBM) of this phase started its drive to bore a 1.4 kilometre long tunnel from Vikaspuri to Krishna Park Extension on the Janakpuri West – R K Ashram Marg corridor in the presence of DMRC’s Managing Director, Dr. Mangu Singh and other senior officials.
- Two parallel circular tunnels for up and down movement will be constructed on this stretch which is a part of the 2.2 kilometre long underground section from Janakpuri West to Keshopur.
- The lowering and assembling process of this giant 73 metre long machine was started in October last year.
- The tunnelling has started from the Vikaspuri area in continuation of the Magenta line tunnel that has been already constructed for the presently operational Botanical Garden – Janakpuri West corridor.
- The tunnel will be constructed approximately at a depth of 14 to 16 metres. About 2,040 concrete rings will be installed in these tunnels.
- Each tunnel will have an inner diameter of 5.8 metres.
- The entire tunnelling work on this stretch is expected to be completed in about 12 month’s time.
- The alignment of tunnel runs along the Outer ring road and below the multi-storied built up structures.
- The tunnel will be built up with proven technology of EPBM (Earth pressure balancing method) with concrete lining made up of precast tunnel rings.
- The tunnel rings are being cast at the fully mechanized casting yard setup at Mundka.
- These concrete segments are cured with steam curing system to achieve early strength.
- This TBM will be able to carry out tunnelling up to 10 metres per day.
- All necessary safety precautions are being taken while constructing the tunnel below the built up structures by monitoring the ground movements with highly sensitive instruments fixed on the nearby structures.
- After completion of tunnelling, this machine will be taken out from retrieval shaft being built with Krishna Park Extension underground station.
- 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.
About Tunnel Boring Machine (TBM):
- 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
