By rosebell
Following completion of an underground tunnel between Chhatarpur Mandir and IGNOU Station on the Tughlakabad-Aerocity corridor, a key landmark has been achieved in Phase 4 Golden Line by the Delhi Metro Rail Corporation (DMRC), that is a joint venture between the Government of India and Delhi.
The IGNOU Station site of the Delhi Metro was the location that the tunnel boring machine’s (TBM) breakthrough occurred; and the TBM successfully broke through at IGNOU Station after boring a 1,475m-long tunnel.
This breakthrough was made using a massive 97m-long TBM, as DMRC stated.
With the aim of advancing the Aerocity-Tughlakabad corridor, two parallel circular tunnels for up and down movement are being built and the next month is scheduled date for breakthrough for the second tunnel.
As one of Delhi Metro’s deepest tunnels, the new tunnel was constructed at an average depth of 26m, whereas the Magenta Line tunnel at Hauz Khas was built at a depth of almost 30m and a total of 1,048 rings, with an inner diameter of 5.8m, were installed. Being casted at a fully mechanised yard in Mundka and steam-cured to achieve early strength, the precast concrete rings were used in this tunnel that has been constructed using the EPBM (Earth Pressure Balancing Method).
The date of commencing tunneling process for this project was 4 December 2023, facing challenges such as a steep gradient and varying geology, including mica and hard rock.
DMRC implemented strict safety measures during tunnel construction beneath existing viaducts and structures. Ground movements were monitored using sensitive instruments on nearby buildings, ensuring no settlement anywhere.
The 40.1km of underground lines are being constructed as part of the Phase and the Aerocity-Tughlakabad corridor comprising 19.3km of underground sections.
In order to digging tunnels with a circular cross-section through various soil and rock types, a TBM is used, which is designed to bore through everything from hard rock to sand, TBMs have advanced tunneling by allowing excavation without disrupting surface structures.
Additionally, it helps in underground work in densely populated urban areas. DMRC has utilised TBMs since Phase 1, and in Phase 3, around 30 TBMs were deployed for the construction of 50km of underground sections in Delhi.
The tunneling drive for Phase 4 was completed in December 2024.
The responsibility of finishing the tunnel boring between the Tughlakabad Airforce launch shaft and Maa Anandmayee Marg Station on the Tughlakabad-Aerocity corridor was up to TBM Amrit, operated by Afcons Infrastructure.
