The Delhi Metro is the largest and busiest rapid transit system in India, serving Delhi and its satellite cities of Ghaziabad, Faridabad, Gurgaon, Noida, Bahadurgarh, and Ballabhgarh. It operates over 2,700 trips daily.

The system currently consists of 10 color-coded lines serving 253 stations with a total length of 348 km, including a mix of underground, at-grade, and elevated stations.

The network’s development was divided into phases. Phase 1 and Phase 2 were completed by 2006 and 2011, respectively. Phase 3 includes 35 underground stations and three new lines, totaling 167 km, and is scheduled for substantial completion by the end of 2020.

The total length of the underground corridors in Phase 3 is 54 km — more than 20 km longer than the total underground sections in Phases 1 and 2 combined — making it one of the most challenging construction stages.

More than 20 tunnel boring machines (TBMs) were used simultaneously to expedite the tunnel work through 10 Dextra Soft-Eyes installed in diaphragm walls. Thanks to the cuttable nature of GFRP (glass fiber reinforced polymer) bars, TBMs can enter or exit shafts and stations in just a few minutes.

Furthermore, 450 sets of active anchors were installed to retain walls during the excavation work. The anchors are also made of GFRP, eliminating the need for anchor removal.

Approximately 2.3 million Bartec couplers were installed to connect rebars in various parts of the concrete structures of the stations. Bartec is a bar-break performance system designed to withstand an ultimate tensile strength of up to 800 MPa.

In addition, 2,800 Shear Key post-tensioning systems were installed in concrete recesses as permanent seismic restrainers for the connection of the elevated metro segments.