National High Speed Rail Corporation Ltd (NHSRCL) has commenced tunnelling works between Bandra Kurla Complex (BKC) and Sawli near Ghansoli for the Mumbai-Ahmedabad Bullet Train Project.
The lowering and assembly of the Tunnel Boring Machine (TBM) has commenced for the construction of 16-km long tunnel through TBM, between Bandra Kurla Complex (BKC) and Sawli (near Ghansoli) in Maharashtra.
The 21-km long tunnel is being constructed for the project between BKC and Shilphata in Maharashtra. The tunnel also features India’s first 7 km long undersea tunnel beneath Thane Creek. Out of 21 kms, 5 km tunnel using NATM methods is already completed and the remaining 16 km through Tunnel Boring Machines (TBM).
The tunnel will be a single tube tunnel of 13.1 m diameter to accommodate twin track. This tunnel will be about 25 to 57 Meters deep from the ground level and the deepest construction point will be 114m below the Parsik hill.
The process began with the lowering of one of the six segments of the main shield, weighing approximately 170 metric tonnes. This segment measures about 8.66 metres in length and approximately 7 metres in width and was lowered at a depth of 56 metres below ground level—equivalent to a 20-storey building, at Vikhroli, Maharashtra.
Two TBMs have been received and the tunnelling operations will commence following comprehensive testing and commissioning.
To lower the TBMs, three (03) shafts have been constructed:
- Shaft 1: Retrieval shaft at BKC
- Shaft 2 in Vikhroli
- Shaft 3 in Sawli (near Ghansoli)
TBM 1 will start from Shaft 2 at Vikhroli and will move towards Shaft 1 of Mumbai Bullet Train station at BKC while TBM 2 will start from Shaft 3 at Sawli and move towards Vikhroli (graphic attached).
The two TBMs, weighing 3080 tons (TBM-1) and 3184 tons (TBM-2) respectively are most advanced tunnelling machines deployed in the country. These advanced TBMs, based on Mix Shield / Slurry technology, are specifically designed to operate in complex geological conditions.
Each TBM measures 95.32 metres in total length and comprises several critical components, including the cutter wheel, main bearing, jaw crusher, erector, main shield, tail shield, and four specialized gantries that support tunnelling operations.
These machines can operate at a maximum cutterhead speed of 4 RPM (revolutions per minute), with a maximum excavation rate of 49 mm per minute, enabling steady and controlled tunnelling progress while maintaining high safety standards.
Technical Specifications:
- No. of TBMs received :2 Nos.
- Weight of TBM 1: 3080 tons
- Weight of TBM 2: 3184 tons
- Cutter head diameter: 13.6 m
- TBM type: Mix Shield / Slurry based
- Length of each TBM: 95.32 m
- Parts of TBM: Cutter wheel, Main bearing, Jaw crusher, Erector, Main shield, Tail Shield, Gantry1-4
- Gantry 1 : Transformers, Operator cabin, grouting pump, STS
- Gantry2 : Segment lifter, grout tank, hose wheel
- Gantry3 : STS Pipe wagon, Cable box
- Gantry 4 : Ventilation duct
- Speed: Max : 4 RPM (revolutions per minute), max excavation rate : 49mm/min
- TBM initial drive: July 2026
- Main drive: October 2026
A dedicated casting yard covering an area of 11.17 Ha for casting tunnel lining for the 16 km TBM portion is already operational in Mahape, Thane district. 77,000 segments will be cast to form 7,700 rings. Special ring segments are being cast for the tunnel lining, each ring comprising nine curved segments and one key segment, with each segment being 2 meters wide and 0.5 meters (500 mm) thick.
This casting yard is equipped with various cranes, gantries, and machines to automate and mechanize the casting operations, ensuring high-quality assurance during the casting and stacking of the segments. Additionally, the facility also includes casting sheds, a stacking area, a batching plant, and a steam curing area.
Various monitoring instruments are being used to ensure safe excavation of the tunnel and all the structures in the nearby area. These include Surface Settlement Points (SSP), Optical Displacement Sensors (ODS) or tilt meters, BRT (By reflect target/3D targets), Strain Gauge for micro strains in tunnel surface, Seismograph for Peak Particle Velocity (PPV) or vibration & seismic wave monitor.
