Colaba-Bandra-SEEPZ Corridor

by Shrutee K/DNS

In Mumbai’s first underground metro, Mumbai Metro Rail Corporation (MMRC) is using TBMs for the Tunneling construction works and the New Austrian Tunnelling Method (NATM) techniques Cross passages and station box construction.

Major activities involved during tunneling are Launching Shaft works, TBM Lowering and Assembling, Segment Casting and Transportation, Tunnel Excavation and Segment lining installation by the TBM, and parallelly Muck disposal by Locomotives and dumpers to the muck dumping sites/land fill queries as identified by MMRC.

TBMs can be operated in closed and open mode depending on the ground/geological conditions

Special Safety Provisions in TBMs and tunnels

Smoke and Fire Detection/Alarm System

Water Sprinkling and Fire Curtain

Dewatering Pumps to tackle flooding

First-aid room and first-aid kits at strategic locations for emergencies

Gas detectors at Cutter Head monitoring presence of toxic gases at the TBM face

Chiller plant to maintain the ambient temperature for workmen

Fire points and extinguishers at 15-30 m

Walkie talkies and telephones are installed at every 100 m for undisturbed communication

Emergency lights at every 50 m for proper illumination

27 Self Rescuers inside the TBM for 25 workmen and five Self Rescuers for the visitors are available at the bottom shaft

5 Close Circuit Breathing Apparatus (CCBAs) for emergency response team to handle fire emergencies

Man Lock provision to access the excavation chamber required for the TBM maintenance

Continuous site monitoring at emergency control room, using CCTV surveillance for early Emergency response in case of any emergencies

Locomotives for transporting muck out of TBM are installed with Speedometer, Speed Governors, Rare-view Cameras, Manchester gates and Track Signalling

Electrical Cables Power supply cables are water proof, dust proof, fire-retardant and produce low smoke and fumes

First-aid rooms available at shaft surface and inside the TBM for workmen. A team of dedicated doctor, first aider, male nurses and technicians equipped with first kit, ambulance, stretcher and resting beds are available round the clock

Eye wash station is provided in the TBM

Some of the basic protocols that are mandatory on the site are:

Training imparted before entering the tunnel:

A 96-hour Workers Safety Training

Confined space safety training

First-aid medical training

Daily Tool Box Talks

Fire-fighting training

An audio-visual site-specific safety induction/brief to all visitors

Use of Personal Protective Equipment (PPE) for any site activity is compulsory

27 Self Rescuers Breathing Apparatus (SRBA) inside the tunnel for the workmen are available. Every visitor is also provided with a self-rescuer at the bottom shaft before entering the tunnel

Emergency ladders and rescue basket is available

Elevated walkways with guard rails and suitable toe boards installed inside the tunnel

Emergency response plans and contact numbers displayed in shaft area

Hyperbaric Interventions During Tunneling

During tunneling operations workers are often required to change the cutter discs tools.

When the TBM is operating in closed air mode, the workers have to work in compressed air environment. This is called Hyperbaric intervention.

Man Lock is provided to allow workmen access to the excavation chamber for replacement of the cutter discs.

Manlock comprises of 2 chambers, first aid box, inspection viewpoints, compressed breathable air supply, relaxation seats, and communication lines with the workers.

Hyperbaric intervention is carried out in the presence of highly trained professionals and supervision.

In case of further emergency and discomfort to the workmen Medical-lock is situated at the Top of Shafts, to further handle the decompression of the workmen who went inside the compressed chambers of more than 1 Bar air pressure.

Approximately 7,600 of manpower, including skilled and unskilled, are on the job at MML3. This is in addition to General Consultants (GC), MMRC personnel, managers and engineers of the civil contractors and various vendors working on the project More than 100 safety signages are placed at each site in Hindi, Marathi and English


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