The Additionally Driven Intermediate Tunnel (ADIT) of 394 meter at Ghansoli in Navi Mumbai for the Mumbai-Ahmedabad Bullet Train Project, has been excavated. This will expedite the construction of 21-km-long tunnel between BKC and Shilphata in Maharashtra.
The 26-meter-deep inclined ADIT will facilitate construction of the 3.3 km (approx.) tunnel through New Austrian Tunnelling Method (NATM), by allowing simultaneous access for tunnelling 1.6 meter (approx.) on each sides. Out of 21 km of tunnelling works, 16 km is through Tunnel Boring Machines and remaining 5 km is through NATM, a release from National High Speed Rail Construction Ltd (NHSRCL) said.
The excavation work for ADIT was started on December 6, 2023, and the entire length of 394 meter is excavated in a short duration of six months. Total 214 controlled blasts were done using 27,515 kg explosives under supervision of experts and high level of instrumentation was used to ensure safe excavation, the release said.
The ADIT of internal dimension: 11 meter X 6.4 meter will give direct vehicular access to the main tunnel during construction and operations and may also be used for the purpose of evacuation process in emergency situation.
A number of monitoring instruments are being used to ensure safe excavation of the tunnel and all the structures in the nearby area. Some of the instruments being used for the work are SSP (Surface settlement Points), ODS (Optical displacement Sensor) or tilt meter for displacement in both axis, 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.
The construction activities related to 21 km (approx.) long tunnel from Mumbai Bullet Train station to Shilphata in the state of Maharashtra is progressing at a fast pace. The 7 km (approx.) stretch of this tunnel will be under the sea at Thane Creek (Intertidal zone). This is the first of its kind tunnel to come up in the country.
The 21 km long tunnel will be a single tube tunnel to accommodate two track meant for up and down tracks. To construct this tunnel, Tunnel Boring Machines (TBMs) with cutter heads of 13.6 meter diameter will be used. Usually 6-8 Meter Diameter cutter heads are used for urban tunnels used in MRTS – Metro system, as these tunnels accommodate one track only.
The under construction three shafts at BKC, Vikhroli, and Sawli will facilitate the construction of 16 km long tunnel through TBMs, the release added.
