On 5 July 2026 India’s largest rail Tunnel Boring Machine (TBM) commenced excavation from the Vikhroli (56 m) shaft for a 6 km single-tube tunnel in the Mumbai section of the Ahmedabad–Mumbai High‑Speed Rail corridor.
TBM and Tunnel Section
- Tunnel type: Single‑tube twin‑track tunnel carrying both up and down tracks over 6 km towards BKC within the 21 km underground Mumbai section.
- TBM dimensions: 13.6 m cutterhead diameter, 96 m length, ~3,100 tonnes; cutterhead rotation ~4 rpm.
- Shaft depth and alignment: Launched from a 56 m deep Vikhroli shaft; alignment passes beneath multi‑storeyed areas, major roads and the Mithi River.
Technology and Construction Details
- TBM type: Advanced Mixshield TBM configured for large‑diameter excavation in mixed geology and high groundwater pressure.
- Pressure control: Uses pressurised bentonite slurry to balance face pressure and limit surface settlement.
- Segmental lining: 77,000 precast concrete segments to form 7,700 tunnel rings; each ring comprises multiple segments totalling ~100 tonnes per ring.
- Waterproofing: Double‑layer EPDM gaskets and hydrophilic seals incorporated for long‑term watertightness.
Support Infrastructure & Monitoring
- Casting yard: Mahape yard (11.17 ha) producing segments for continuous ring erection.
- Site systems: On‑site water and slurry treatment, ready‑mix concrete for grouting, and real‑time monitoring systems for TBM performance and ground movement.
IASPOINT Booster Facts
- EPDM: Ethylene propylene diene monomer rubber used for durable gasketing in tunnel linings.
- Hydrophilic seals: Swell on contact with water to seal joints against leakage.
- Mixshield principle: Temporary face support via pressurised slurry enabling safe tunnelling below high water table and urban assets.