The dream Bangabandhu Tunnel under Karnaphuli River is about to become reality as 50 percent of its excavation has been completed revealing the tunnel halfway. The Bangabandhu Tunnel, the country’s first and the longest in South Asia, 31 meters below the Karnaphuli River, is being constructed with a monster-shaped Tunnel Boring Machine TBM 95 meters in length.
Officials said, the highest safety and security will be ensured during the construction. The tunnel, officially known as the Bangabandhu Sheikh Mujibur Rahman Tunnel, is expected to go into operation for public use in 2022. “About 50 percent construction work of the tunnel under Karnaphuli River has been completed till date,” project director (PD) Engineer Harunur Rashid Chowdhury told Bangladesh Post.
“And the highest safety and security will be ensured there. We expect that the installations of rings in these tubes will be finished by next May or June.” At present, one of the two tubes of the tunnel have been constructed at 1,228 meters length, which is now half way under the River Karnaphuli. “We are hopeful pf completing the project within the targeted period of December 2022,” The PD added. A source of Bangladesh Bridge Authority BBA said, “A tunnel boring machine (TBM), also known as a "mole" is being used to excavate the Bangabandhu Tunnel consists of a shield (a large metal cylinder) and trailing support mechanisms which is using Shield Driven Method SDM.”
He said, “A huge rotating cutting wheel is located at the front end of the shield. Behind the cutting wheel there is a chamber where the excavated soil is either mixed with slurry or left as-is Earth Pressure Balance or EPB shield. Behind the chamber there is a set of hydraulic jacks supported by the finished part of the tunnel which are used to push the TBM forward. Once a certain distance has been excavated (roughly 1.5–2 meters (5–7 ft)), a new tunnel ring is built using the erector.”
The four lane tunnel route will pass through under the river close to Naval Academy at Potenga of Chattogram city on one side and Korean Export Processing Zone (KEPZ) and Karnaphuli Fertilizer Company (KAFCO) at Anowara upzila on the other side. A visit to the site revealed the progress of the works of the tunnel. Engineers said that the construction works so far involves 1,228 meters long excavation of soil with 614 rings installed. The tunnel is 4.9-meter-high and 11.4 meters wide.
If favorable weather prevails and no natural calamities take place the installation of rings in the two tubes of 2450 meters each will be completed by next May or June next, they said. Officials inform, the distance between the two tubes is about 12 meters inside the tunnel. There will be three cross passages between the two tubes, so that it can be accessed when needed.
The emergency exit will be placed at seven places at the bottom of each tube. There will be enough air and oxygen ventilation system inside the tunnel. Necessary rescue teams and special fire service teams will also be kept on standby. In the meantime, the acquisition of 383 acres of land for the tunnel’s approach roads has also been completed.
An approach road of 4.89 kilometres alongside 740 meters of bridge linking the tunnel in Anowara and 500 meters in Potenga is being constructed. Prime Minister Sheikh Hasina and the President of China Xi Jinping laid the foundation stone of the tunnel on October 14, 2017. Prime Minister Sheikh Hasina inaugurated the boring work of the tunnel in February last.
The estimated cost of the tunnel is Tk 9,880 crore, where Chinese Exim Bank will provide Tk 5,913 crore. The Government of Bangladesh is arranging the rest. Chinese firm ‘China Communication Construction Company Ltd (CCCC), has been appointed as consultant for the tunnel. The tunnel is expected to make communication between Chattogram and Cox’s Bazar easier alongside reducing traffic congestion on two bridges over the Karnaphuli River.