In a significant development for the Mumbai-Ahmedabad bullet train project, a 394-meter-long Additionally Driven Intermediate Tunnel (ADIT) at Ghansoli has been successfully excavated. This ADIT will play a crucial role in facilitating the construction of a 21-km-long tunnel between BKC and Shilphata in Maharashtra.
The 26-meter-deep inclined ADIT will support the construction of a 3.3-km tunnel segment using the New Austrian Tunnelling Method (NATM), allowing simultaneous tunnelling approximately 1.6 meters on each side. Of the 21 km of tunnelling works, 16 km will be completed using Tunnel Boring Machines (TBMs), with the remaining 5 km utilizing NATM.
Excavation of the ADIT began on December 6, 2023, and the 394-meter length was excavated within six months. A total of 214 controlled blasts were executed, using 27,515 kg of explosives under expert supervision. High levels of instrumentation were employed to ensure safe excavation.
The ADIT, with internal dimensions of 11 meters x 6.4 meters, will provide direct vehicular access to the main tunnel during construction and operations. It may also serve as an evacuation route in emergencies. To ensure safe excavation and the integrity of nearby structures, several monitoring instruments are in use.
These include Surface Settlement Points (SSP), Optical Displacement Sensors (ODS) or tilt meters for displacement measurement in both axes, By Reflect Target (BRT) for 3D target monitoring, Strain Gauges for detecting micro strains on the tunnel surface, and Seismographs for monitoring Peak Particle Velocity (PPV) and seismic waves.
Construction of the 21-km tunnel from Mumbai Bullet Train station to Shilphata is progressing rapidly. Notably, a 7-km stretch of this tunnel will pass under the sea at Thane Creek, making it the first tunnel of its kind in India. The 21-km tunnel will be a single tube accommodating two tracks for both directions. To construct this tunnel, TBMs with cutter heads of 13.6 meters in diameter will be used, significantly larger than the typical 6-8 meter diameter heads used in urban metro tunnels, which accommodate only one track.
Three shafts currently under construction at BKC, Vikhroli, and Sawli will facilitate the construction of the 16-km tunnel segment using TBMs. This achievement marks a major milestone in the Mumbai-Ahmedabad Bullet Train Project, highlighting the rapid progress and the advanced engineering methods being employed. The successful completion of the ADIT will expedite the overall construction timeline, bringing the ambitious high-speed rail project closer to reality.
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