NEW DELHI: The Delhi Metro Rail Corporation on Thursday began tunneling work on 1.4 km stretch from Vikaspuri to Krishna Park Extension on the Janakpuri West-RK Ashram Marg corridor of its phase-IV project. Two circular tunnels for a two-way movement will be constructed on this stretch, which is a part of the 2.2 km-long underground section from Janakpuri West to Keshopur.
The lowering and assembling process of a giant 73-metre-long machine started in October last year, said a DMRC official. The tunneling has started from the Vikaspuri area in continuation of the Magenta Line tunnel that has already been constructed for the operational Botanical Garden-Janakpuri West corridor.
Officials said 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 work is expected to be completed in about 12 month. The alignment of the tunnel runs along the Outer Ring Road and below the multi-storied built-up structures,” said DMRC.
The tunnel will be built 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 a fully mechanized casting yard at Mundka. The Tunnel Boring Machine (TBM) will be able to carry out tunneling up to 10 metres per day, said the officials.
The TBM is a device used to excavate tunnels with a circular cross-section through a variety of soil and rock strata. “All 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 nearby structures.
After tunneling is complete, this machine will be taken out from the retrieval shaft being built at Krishna Park Extension underground station,” said Anuj Dayal, Executive Director, Corporate Communications, DMRC. Of the approved corridors of Phase-IV work, about 27 km will be underground. The Janakpuri West-RK Ashram Marg corridor will have 7.74 km underground sections.