A major milestone in DMRC’s Phase 4 work was achieved on Thursday 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.
A senior DMRC official said that 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 the tunnel runs along the Outer ring road and below the multi-storied built up structures,” he said.
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 a steam curing system to achieve early strength. This TBM will be able to carry out tunnelling up to 10 metres per day, he added.
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. TBMs are especially useful for underground tunnelling work in congested urban areas.