By Following the arrival of a refurbished 6.52m diameter Terratec EPBM, Contractor HCC/VLCC JV is setting up to begin tunneling on Line-8-Magenta Line Phase 4 DC-06 on the Delhi Metro in India.
The JV started work to build the first tunnel ring section after a successful Site Approval Test for the construction of a 2.03km underground extension of the 38.235km Magenta Line of the Delhi Metro from the Vikaspuri Park Shaft to the Vikaspuri Ramp near Keshopur. Two tunnels (for up and down motion) with a length of 1400 m between Vikaspuri and Krishna Park E will be bored as part of this tunneling drive.
In previous DMRC phases, the contractor preferred a Terratec Ø6.52m EPBM with a conventional soil setup, fitted with a Spoke-Like Cutter Head with a 57 percent opening ratio that has been shown to be very successful in excavating this type of soil. Tunnels for Delhi Metro project CC-34 and Lucknow Metro project LKCC-06 have previously been completed for this refurbished unit.
The Cutterhead was designed to enable the cutting tools to be substituted for 17 ” roller disk cutters, allowing the TBM to drill through the D-walls and cope with any unforeseen obstacles, such as old wells or foundations, on its path. The geology consists of silty sand, fine sand & sandy silt, and silt of clay.
The segment lining will be made of RC segments with an outer diameter of 6,350mm, inner diameter of 5,800mm and width of 1,400mm. The total distance that the TBM will bore to is approximately 2,030m.
At an estimated depth of 14-16m, the tunnel can be excavated. As the drives advance, the machines can mount Universal-style reinforced concrete, pre-cast lining rings comprising five segments + key. A 365m long ramp and approximately 220m long station are included in this section, so approximately 2100 segments will be built.
In January 2020, DMRC approved the contract for the construction of twin tunnels from the Vikaspuri Park Shaft to the Vikaspuri Ramp to the HCC-VCCL consortium, with a single underground station at Krishna Park Extension under contract package DC-06 of Phase 4 Delhi Metro. It is estimated that the work will be finished in 36 months.
