Bangabandhu Tunnel can withstand 7.5 magnitude quake

 Located in an area prone to tremors and cyclones, the Bangabandhu Tunnel is an engineering marvel, boasting South Asia's first seismic resilience of up to magnitude 7.5 and the extraordinary capacity to endure eight times the standard weight pressure.

As the tunnel was constructed beneath the point where the Karnaphuli River converges with the Bay of Bengal, proactive measures have been implemented to fortify it against cyclones and tidal surges.

Furthermore, cutting-edge technology has been employed to ensure the tunnel's safety, encompassing electricity supply, fire prevention, and essential drainage systems.

The project engineers told The Business Standard that the tunnel was subjected to underwater vibration monitoring before construction. Subsequently, taking that into account, vibration capacity was determined.

In engineering terms, this tunnel is built to withstand ground acceleration from 0.22g (gravity force) to 0.28g, setting a South Asian record for seismic resilience at a magnitude of 7.5 on the Richter scale — surpassing the Bangabandhu Bridge's 0.15g.

The main tunnel is located 42.80 metres below the water surface. During construction, the tunnel withstood up to 5 bar (unit of pressure). It was originally supposed to be capable of handling 6 bar, but it currently is capable of withstanding 8 bar of standard pressure.

High-speed pumps with sensors

Four floodgates, with two for each tube, have been installed on the tunnel's openings to safeguard it during cyclones, high tides, floods, or natural disasters. Additionally, rain shelters have been constructed at both ends of the tunnel.

To prevent potential accidents from tunnel collapse or water leakage, a comprehensive drainage system has been implemented throughout both tubes.

Each tube is equipped with two active pumps and one backup pump, totalling six pumps capable of discharging one cubic metre of water per second. These pumps are sensor-controlled, automatically activating when water is detected.

110 CCTV cameras covering 360 degrees

A total of 110 CCTV cameras with 360-degree coverage have been installed to continuously monitor the tunnel, automatically displaying accident alerts on the digital screens at the tunnel entrances.

Additionally, fire hydrants are placed every 50 metres for firefighting, and fire service stations are under construction on both sides of the tunnel, with a standby fire truck ready at all times. Fireproof and decorative boards adorn the tunnel interior.

Top-notch scanners 

Two 13-tonne scanners, each spanning 50 metres in length and 10 metres in width, have been strategically placed for two-phase cargo vehicle inspections in the tunnel to bolster security measures.

In the first phase, a low-dose radiation scan clears heavy vehicle drivers for any anomalies signalled by a green light.

In the second phase, the driver disembarks, and a thorough, high-level radiation scan is conducted on open or covered cargo at the rear of the vehicle, a process typically conducted at ports. The whole process will take just two minutes.

Scanner installation was a mid-project addition and not initially budgeted in the Project Development Plan (DPP).

The government has contracted with the China Communication Construction Company Limited (CCCC) for a five-year agreement covering toll collection, tunnel maintenance, scanner installation, and operation, amounting to Tk983.82 crore.

Approximately Tk300 crore is allocated for four scanners, with two already installed and two more in progress. These scanners, provided by UK-based company Varex Imaging, were supplied by Bangladeshi company Global Distributor.

The tunnel also has an Under Vehicle Surveillance System (UVSS), which captures images of the lower portions of large vehicles to check for explosive devices.

Two UVSS units are located at the Anwara entrance, while three are stationed at the Patenga entrance. To maintain tunnel safety, weighing scales have been placed at both tunnel ends, with three scales in each tube for a total of six, ensuring heavy vehicles adhere to the specified axle load.

Vehicles exceeding this limit can proceed only after unloading excess cargo or can return through a cross-passage for safety reasons.

Three-phase power supply system

Project Director Md Harunur Rashid Chowdhury told TBS that the tunnel employs advanced technology, and each tunnel requires 5 MW for a total of 10 MW of electricity to be fully operational.

To ensure power supply reliability, two 15 MW substations are in place at the tunnel's ends, Patenga and Anwara, each connected to two separate lines by the Bangladesh Power Development Board.

In the event of a power outage, online UPS systems provide an immediate two-hour backup, followed by generator backup for up to 10 hours, featuring two 800KVA and one 200KVA diesel-powered generator in a tube.