DMRC Achieves Engineering Milestone: Tunnel Built Under Operational Red Line Without Disruption
Delhi Metro completes a complex tunnel beneath the Red Line at Pulbangash for the Magenta Line Phase-IV extension, using advanced soil strengthening and continuous monitoring to ensure full safety.
The Delhi Metro Rail Corporation (DMRC) has successfully completed a highly challenging underground tunnel for the Magenta Line Phase-IV extension, passing directly beneath the operational Red Line at Pulbangash without affecting train operations. This achievement highlights DMRC’s advanced engineering capabilities and its commitment to safe expansion in densely populated areas.
The tunnel, located between Pulbangash and Sadar Bazar, had to be built below a viaduct that carries lakhs of passengers daily and rests on sensitive open foundations. To ensure complete structural safety, DMRC strengthened the soil using Tube-a-Manchette (TAM) grouting, drilling 180 boreholes and injecting high-strength cement grout to stabilise the ground before excavation.
Throughout the operation, DMRC deployed a network of real-time monitoring instruments—surface settlement markers, inclinometers, pier tilt meters, load cells and an Automatic Total Station. Engineers monitored the data round the clock, and all readings remained within safe limits, allowing tunnelling to proceed smoothly.
With the down-line tunnel now complete, work on the up-line section is underway. The project forms part of Delhi Metro’s Phase-IV expansion, which will further strengthen connectivity on the Magenta Line and support Delhi’s growing mobility needs.
This successful tunnelling operation, completed without a single day of service disruption, reflects DMRC’s ability to execute complex urban infrastructure works with precision, safety and technological excellence.