How India Builts Underwater Metro Station?

India has built an underwater metro in Kolkata, which is the first of its kind in the country. The project involved constructing a 16.6 km metro line, of which 10.8 km runs under the Hooghly River.

How India Builts Underwater Metro Station?

Let's see how these big projects were carried out so that we can learn from here.

Planning and Designing Phase (2009-2010)

The planning and designing phase of the Kolkata Metro Line 2 project started in 2009. The initial plan was to build a metro line that connects the eastern and western parts of Kolkata, reducing travel time and easing traffic congestion. The Kolkata Metro Railway Corporation Limited (KMRCL) was responsible for implementing the project.

The design phase involved studying the geological, hydrological, and environmental factors that could affect the project's execution. The project's engineers and architects designed the metro line to withstand the pressure and currents of the Hooghly River.

Construction Phase (2011-2019)

The construction phase of the project began in 2011, and the entire project was expected to be completed by 2015. However, several unforeseen delays caused the project to be delayed, and it finally opened for commercial operations in 2020.

A. Building the Tunnel (2011-2014)

The first step in constructing the underwater metro was to build a tunnel that would run under the Hooghly River. The tunnel was built using an Earth Pressure Balance Tunnel Boring Machine (EPB TBM). This type of tunneling machine uses hydraulic jacks to exert pressure against the tunnel's walls while simultaneously excavating the soil.

The excavation of the tunnel took about two and a half years, with construction workers working round the clock in shifts. The tunnel's construction took place in two stages - the first stage involved building the upstream tunnel from Howrah Maidan to Mahakaran Station, and the second stage involved building the downstream tunnel from Howrah Maidan to Salt Lake Sector-V Station.

B. Building the Stations (2014-2019)

Once the tunnel was complete, the next step was to build the stations. The stations were constructed using a cut-and-cover method. This involved digging a trench, building the station, and then covering it back up with a concrete slab to form the station roof.

The construction of the stations took about five years, with each station taking approximately six months to build. The stations were equipped with special facilities for disabled people, including lifts and ramps.

C. Installing Tracks and Electrical Equipment (2015-2019)

The next step was to install the tracks and electrical equipment needed to run the metro trains. The tracks were installed in the tunnel, and electrical equipment was installed in the stations. The electrical equipment included a power supply system, signaling system, communication system, and ventilation system.

The underwater section of the metro has a special signaling system that can detect any abnormalities in the tunnel's water pressure, and the trains have an automatic shutdown mechanism in case of an emergency.

Testing and Commissioning Phase (2019-2020)

The final phase of the project was the testing and commissioning phase. The metro trains were tested in the tunnel, and the electrical systems were tested in the stations. The trains were run for about 12,000 km to test their performance and safety.

Once everything was working properly, the metro line was opened to the public in 2020. Today, the Kolkata Metro Line 2 is a significant milestone for India's infrastructure development and is a testimony to the country's engineering prowess.

Techniques Used to Build the Underwater Kolkata Metro Line 2

Earth Pressure Balance Tunnel Boring Machine (EPB TBM)

The EPB TBM was used to dig the tunnel under the Hooghly River. The TBM was equipped with hydraulic jacks to exert pressure against the tunnel's walls while simultaneously excavating the soil. This technique helped stabilize the tunnel's walls and prevent water seepage from the riverbed.

Cut and Cover Method

The cut-and-cover method was used to build the stations. This technique involves digging a trench, building the station, and then covering it back up with a concrete slab to form the station roof. The technique was used because it is cost-effective and less time-consuming than other methods.

Specialized Signaling System

The underwater section of the Kolkata Metro Line 2 has a specialized signaling system that can detect any abnormalities in the tunnel's water pressure. The signaling system is designed to shut down the trains automatically in case of an emergency.

Automated Train Control System

The Kolkata Metro Line 2 uses an automated train control system that allows for the smooth operation of the trains. The system uses a central control room to monitor and control the movement of the trains, ensuring their safety and efficiency.

Robust Construction Materials

The construction materials used for the Kolkata Metro Line 2 were selected for their strength and durability. The tunnel's walls were built using reinforced concrete, which can withstand the pressure and currents of the Hooghly River. The stations were built using precast concrete, which is resistant to corrosion and erosion.

Environmental Considerations

The construction of the Kolkata Metro Line 2 took into account the environmental impact of the project. The project's engineers and architects designed the metro line to minimize the disruption to the local environment. Special measures were taken to prevent soil erosion, water pollution, and air pollution.

The End Notes

The construction of the Kolkata Metro Line 2 was a significant engineering feat that involved the use of advanced techniques and materials. The project's successful completion is a testament to India's engineering prowess and its commitment to infrastructure development. The metro line has brought significant benefits to Kolkata, reducing travel time, easing traffic congestion, and improving the quality of life for its residents.

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