DMRC Completes Complex Tunnel Construction Under Red Line at Pulbangash

The Delhi Metro Rail Corporation (DMRC) has achieved a major engineering milestone in its Phase 4 expansion by completing a highly challenging tunnelling operation beneath the operational Red Line at Pulbangash—without stopping or slowing train services.

The tunnel forms part of the Janakpuri West–RK Ashram Marg extension of the Magenta Line and connects the Pulbangash–Sadar Bazar stretch.

DMRC engineers said the task was exceptionally sensitive because the Red Line viaduct at the site rests on open foundations with a balanced cantilever span. Tunnelling directly below such a structure required extraordinary safety precautions.

To ensure ground stability, DMRC implemented a detailed ground-strengthening plan using the TAM (Tube-a-Manchette) grouting technique. Around 180 boreholes were drilled near the existing pier and injected with high-strength cement grout to stabilise soil, fill voids and prevent settlement during TBM operations.

Throughout the process, trains continued to run normally on the busy Red Line, marking this as a significant technical accomplishment for DMRC’s Phase 4 development.