Overview
The National High Speed Rail Corporation Limited (NHSRCL) has started lowering and assembling a TBM for a 16 km stretch of the Mumbai‑Ahmedabad Bullet Train corridor. The work marks a critical phase in constructing a 21 km tunnel that includes India’s first seven‑km under‑sea segment beneath Thane Creek.
Key Developments
- Lowering of one 170‑tonne shield segment (8.66 m × 7 m) at a depth of 56 m in Vikhroli.
- Two TBMs will be launched from three shafts: retrieval shaft at BKC, and shafts at Vikhroli and Sawli (near Ghansoli).
- TBM‑1 will advance from Vikhroli towards BKC; TBM‑2 will move from Sawli towards Vikhroli, creating a single‑tube tunnel of 13.1 m diameter for twin tracks.
- The tunnel depth will vary between 25 m and 57 m, reaching a maximum of 114 m below Parsik Hill.
Important Facts
• The 21 km tunnel comprises 5 km built using the NATM and the remaining 16 km via TBM.
• Each TBM measures 95.32 m in length and includes a cutter wheel, main bearing, jaw crusher, erector, main shield, tail shield, and four specialised gantries.
• Maximum cutter‑head speed is four RPM, delivering an excavation rate of up to 49 mm per minute, ensuring controlled progress and safety.
UPSC Relevance
The project illustrates the intersection of infrastructure development (GS3) and technology adoption. Understanding TBM technology, NATM, and under‑sea tunnelling helps answer questions on large‑scale transport projects, financing mechanisms, and environmental clearances. The involvement of NHSRCL showcases the role of a dedicated public sector undertaking in executing strategic rail corridors, a topic relevant to governance and public‑private partnership discussions (GS2, GS3).
Way Forward
• Completion of the remaining TBM‑driven stretch is expected to follow rigorous testing and commissioning, with an emphasis on safety and minimal disruption to surrounding areas.
• Continuous monitoring of geological conditions will guide adjustments in tunnelling parameters, especially for the under‑sea segment.
• Successful execution will set a precedent for future high‑speed rail and metro projects across India, encouraging the adoption of advanced tunnelling technologies and strengthening the nation’s transport infrastructure.