Delhi Metro Phase IV: The Delhi Metro Rail Corporation (DMRC) started the first tunnelling drive for Delhi Metro Phase IV on the Janakpuri West – R K Ashram Marg corridor. A tunnel boring machine (TBM) of the phase began the drive to bore a 1.4 kilometre long tunnel from Vikaspuri to Krishna Park Extension area. Two parallel circular tunnels for the upwards and downwards movement will be constructed on the 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 2020, according to Delhi Metro Rail Corporation. (Also Read: Atmanirbhar Bharat: Delhi Metro Signs Pact To Develop Indigenous Rail Systems )
The tunnelling started from the Vikaspuri area in continuation of the Delhi Metro Magenta line tunnel that has been already constructed for the presently operational Delhi Metro 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 the 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 months. 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. The concrete segments are cured with steam curing system to achieve early strength. The TBM will be able to carry out tunnelling up to 10 metres per day. (Also Read: Here’s All You Need To Know About India’s First Driverless Train For Delhi Metro )
After the completion of tunnelling, the machine will be taken out from retrieval shaft being built with Krishna Park Extension underground station. As part of the Delhi Metro Phase 4 work approved so far, about 27 kilometres of underground lines will be constructed. The Janakpuri West – RK Ashram Marg corridor will have a total of 7.74 kilometres of underground section.
A tunnel boring machine is 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. With TBMs, tunnels can now be bored without disturbing the buildings and other structures on the surface. The machines are especially useful for underground tunnelling work in congested urban areas.