Underground tunnel on Tughlakabad-Aerocity corridor completed
The Delhi Metro Rail Corporation (DMRC) completed the underground tunnel between Chhatarpur and Chhatarpur Mandir station in Phase 4 of Golden Line on Saturday, officials said.
A 97-m-long tunnel boring machine (TBM) broke through on Saturday morning at the Chhatarpur Mandir station after boring an 860-m-long tunnel, they said. Two parallel circular tunnels for up and down movement have been constructed on this stretch as part of the Aerocity-Tughlakabad corridor.
The breakthrough on the other parallel tunnel was achieved on August 21, the officials added. This new tunnel has been constructed at an average depth of approximately 12 m. As many as 613 rings had been installed in the tunnel, with an inner diameter of 5.8 m, DMRC Principal Executive Director Anuj Dayal said.
The tunnelling work involves numerous challenges such as shifting a 66 KV electrical high-tension line. Additionally, the TBM had to cross below the existing Yellow Line viaduct without disrupting metro train operations on the line, he said.
The tunnel has been built using the technology of earth pressure balancing method (EPBM) with a concrete lining made of precast tunnel rings. These tunnel rings were cast at a fully mechanised casting yard set up at Mundka. The concrete segments were cured with a steam curing system to achieve early strength, Dayal said.
All necessary safety precautions were taken during the construction of the tunnel below the existing viaduct and built-up structures. Ground movements were monitored with highly sensitive instruments fixed on nearby structures, ensuring that there was no settlement anywhere, he said.
As part of the Phase-4 work approved so far, 40.109 km of underground lines are being constructed. The Aerocity-Tughlakabad corridor had underground sections totalling 19.343 km, they said.
In Phase 3, when approximately 50 km of underground sections were built, about 30 TBMs were deployed in the national capital, he added.
