Published Date: 09-04-2026

The lowering and assembly of the Tunnel Boring Machine (TBM) has commenced for the construction of a 16 km long tunnel between Bandra Kurla Complex (BKC) and Sawli (near Ghansoli) in Maharashtra for the Mumbai-Ahmedabad Bullet Train Project.

The 21 km long tunnel is being constructed between BKC and Shilphata in Maharashtra. It includes India’s first 7 km long undersea tunnel beneath Thane Creek. Out of the total length, 5 km tunnel using NATM method is already completed and the remaining 16 km will be constructed using TBMs.

The tunnel will be a single tube tunnel of 13.1 m diameter to accommodate twin tracks. The depth of the tunnel will vary from 25 to 57 meters below ground level, with the deepest point reaching 114 meters below Parsik hill.

The process began with the lowering of one of the six segments of the main shield, weighing approximately 170 metric tonnes. The segment measures about 8.66 meters in length and 7 meters in width and was lowered at a depth of 56 meters below ground level at Vikhroli, Maharashtra.

Two TBMs have been received and tunnelling operations will commence after testing and commissioning.

TBM Launch & Shaft Details:

• Shaft 1: Retrieval shaft at BKC
• Shaft 2: Vikhroli
• Shaft 3: Sawli (near Ghansoli)
• TBM 1 will start from Vikhroli towards BKC
• TBM 2 will start from Sawli towards Vikhroli

The two TBMs, weighing 3080 tons (TBM-1) and 3184 tons (TBM-2), are among the most advanced tunnelling machines deployed in India. These machines use Mix Shield / Slurry technology and are designed for complex geological conditions.

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.