The Renaissance of the Ancient Silk Road: Celebrating a Thousand Years of Friendship Between China and Bangladesh

On October 28, 2023, the Bangabandhu Sheikh Mujibur Rahman Tunnel in Bangladesh, supervised by the collaboration of CIECC Engineering Management Consulting Co., Ltd. and CIECC Engineering Company Limited, constructed by China Communications Construction Company (CCCC) and implemented by China Road & Bridge Corporation (CRBC), was officially opened to traffic. With the tunnel’s opening, the travel time across the Karnaphuli River has been reduced from the previous 3 hours to just 20 minutes.

As a flagship project of the Belt and Road Initiative, the tunnel sets multiple records in Bangladesh: it is the first underwater tunnel in South Asia and the first large-diameter underwater shield tunnel constructed by Chinese enterprises abroad. The Bangabandhu Sheikh Mujibur Rahman Tunnel is a crucial link in the Bangladesh-China-India-Myanmar (BCIM) Economic Corridor, serving as an underwater bridge that connects the dreams of a new era, the “Chinese Dream” and the “Golden Bangladesh”.

The completion and opening ceremony of the Bangabandhu Sheikh Mujibur Rahman Tunnel was held on October 28, 2023. The event was attended by the Prime Minister of Bangladesh, Sheikh Hasina, and the Chinese Ambassador to Bangladesh, Yao Wen. The heads of the CIECC supervisory team and representatives from all participating units were also present at the ceremony.

01 Landmark Project: The First Overseas Endeavor of a Riverbed Tunnel Built to Chinese Standards

The Bangabandhu Sheikh Mujibur Rahman Tunnel project, formerly known as the Karnaphuli River Bottom Tunnel project, was signed under the witness of leaders from China and Bangladesh. Located in Chittagong, Bangladesh, near the mouth of the Karnaphuli River, the tunnel connects the river’s east and west banks. The total length of the route is 9.3 kilometers, with a designed speed of 80 kilometers per hour, supporting two-way, four-lane traffic. The shield tunnel section is 2,450 meters long with a diameter of 11.8 meters. The connecting roads on the east and west banks span 6.36 kilometers, and the reinforced concrete bridge - the KAFCO Bridge - stretches for 727 meters. This project, utilizing Chinese standards, Chinese equipment and managed by Chinese enterprises, represents a successful exploration of China’s complete industrial chain for tunnel construction overseas and has become a shining business card for “China Tunnel” abroad.

Hard work reaps rewards, as each step is firmly imprinted over nearly six years. Officially commenced on December 5, 2017, the builders overcame numerous technical challenges and difficulties such as the pandemic and material shortages. Through persistence and overcoming each obstacle, they continuously marched from victory to victory.

From the outset, the project was a sprint, starting with intense challenges. To begin the shield tunneling, the main structure of the west bank working pit and the cut-and-cover section (90 meters) had to be completed by August 8, 2018. The construction schedule was tightly controlled, measured in hours, and upon self-inspection, each process had to be immediately accepted. During this time, Bangladesh was in the midst of the monsoon season, characterized by intense heat and swarms of mosquitoes. The supervisory team worked tirelessly, sweating day and night at the concrete stations and during the acceptance of the working pits and main structures - memories that remain vivid years later.

To strictly control the quality of construction, the CIECC supervisory team implemented around-the-clock inspections. During the construction of the KAFCO Bridge deck, the acceptance of the tunnel segments, and the checking of the cut-and-cover tunnel structures, the team always adhered to principles and actively communicated with the construction units upon encountering non-conformities. Inspecting every joint of the column and beam structures in the east bank toll canopy, the cut-and-cover tunnel entrance canopy, the flood prevention door steel structures, as well as the installation of fireproofing and decorative panels inside the tunnel, the team ensured quality and safety at every stage. Seeing the media’s high praise for the Bangabandhu Sheikh Mujibur Rahman Tunnel project as successful, beautiful, safe, reliable and aesthetically pleasing, everyone felt that all the hard work and effort were worthwhile.

02 Showcasing Prowess: Building the Hard-Core Quality of Shield Machines

“To do a good job, one must first sharpen their tools”, goes the old saying, and the selection of the shield machine is crucial for the smooth construction of the tunnel. At the beginning of the project, the CIECC supervisory team conducted a meticulous review of the geological survey report. In conjunction with the completed foundation data of other building projects at the same location, they collaborated with the CCCC General Manager Department and the tunnel expert group from the construction units to decide on using a slurry balance shield machine independently developed and manufactured by CCCC Tianhe Mechanical Equipment Manufacturing Co., Ltd. (referred to as CCCC Tianhe). The shield machine is 94 meters long, with a cutter head diameter of 12.12 meters and a total weight of over 2,200 tons. All tunnel segments used in the project were uniformly prefabricated in China, totaling over 20,000 segments, with each segment weighing approximately 12 tons.

The CIECC supervisory team dispatched experienced concrete structure engineers and test engineers with prior experience in tunnel segment supervision to reside at the segment prefabrication plant. They rigorously oversaw every aspect from the acceptance of the segment steel molds and embedded parts, re-inspection of concrete raw materials, admixtures and steel bar sampling, to the production, processing and installation of the steel skeletons for the segments, and the installation of embedded parts within the molds. They strictly controlled quality acceptance according to the standards and design drawings, focusing on the concrete pouring process for each segment and the external quality after demolding. They comprehensively monitored segment leakage, bending resistance tests, and the tri-ring level assembly inspection. Production started on April 9, 2018, and after 1,071 days, on March 16, 2021, a total of 2,513 rings (20,110 segments) of shield tunnel segments were manufactured to high-quality standards and shipped out of the factory. They were then delivered by sea to the construction site at Chittagong, Bangladesh.

03 Tackling Toughness: Suggesting Soil Improvement Plans for Geological Strata

Biting through the “Tough Bone” of the construction schedule and traversing the mechanical “Flame Mountain”, the project faced new challenges due to unique geological conditions. To address the shield machine’s launching and receiving conditions in the riverbed’s water-rich, fine sandy strata, the CCCC General Manager Department, the CIECC supervisory team and the tunnel expert group from the construction units had drawn on the successful experience of similar domestic tunnels to propose a construction plan that included using steel casings to aid the shield machine during entry and exit, as well as its rotation.

The CIECC supervisory team implemented strict quality control measures for the shield machine’s initial safety and the end-head’s freezing and reinforcement construction process. They ensured that the length of each freezing pipe was inspected, the inclination of freezing pipes was monitored, the installation quality of the freeze unit was verified, and the pressures and temperatures of the freezing brine and clean water were dynamically monitored. They also checked the quality of the shield machine’s cutter head, main drive and shield body assembly, witnessed the magnetic particle and ultrasonic testing of welds, and measured the roundness and flatness of the cutter head’s main drive to ensure the installation meets quality standards. The CIECC team placed a strong emphasis on the systematic performance tuning of the shield machine, meticulously inspecting each component, including the segment erector, cutter head’s electrical current and voltage, assembler’s load, synchronous grouting, the circulation filtration system, mixer, elevation motors of the assembler, secondary grouting electric hoist, fire system, slurry circulation, sewage pumps and air storage tanks. They worked closely with CCCC Tianhe and the construction units to ensure all components meet the required specifications.

Described as a “steel pangolin”, the shield machine conquered rock and walls, with builders overcoming challenges such as controlling the machine’s posture with innovative technologies. The left-line tunnel, influenced by the stratigraphy of the Karnaphuli riverbed’s iron plate sand layer — soft above and hard below — faced deviations in the shield’s posture and segment misalignment beyond the preset warning levels during excavation. To address these issues, the CCCC General Manager Department, the CIECC supervisory team and the tunnel expert group from the construction units held several specialized meetings and commissioned domestic university experts in geological structures to investigate, analyze, and propose targeted solutions for improving the soil conditions. The CIECC team also supervised the high-pressure rotary jet grouting pile construction around the clock, sampling and measuring key parameters such as cement usage, cement slurry density and grouting pressure. These measures helped stabilize the posture of the shield machine. During the replacement of the cutter tools and tail brushes in the left-line tunnel, the CCCC General Manager Department and the CIECC supervisory team worked with the construction units to carefully assess each step for safety risks, evaluate special construction plans, and after several iterations, finalized secure and reliable construction steps and measures.

The CIECC supervisory team conducted 24-hour monitoring during construction, strictly reviewing the alignment of system instrument parameters with the construction plan, ensuring the safety of personnel entering pressurized areas. Drawing on experience from the left-line tunnel, the team diligently supervised the cutter head tool transformation process after a 180-degree rotation of the shield machine with its steel casing and ball base at the East Bank working pit. They verified each tool model, ensured the quality of tool installations and monitored the non-destructive testing of the welds on the tools. Post-upgrade, the right-line tunnel excavation achieved “zero replacement of cutter tools and tail brushes”.

Under starry skies and with the moon   above,

 they turn challenges into triumph.

Brave,   smart, and unyielding,

they climb   mountains and cross nations,

to bring the   people of Bangladesh a fast and comfortable travel experience.

As the   premiere underwater tunnel in South Asia by a Chinese company and a crucial   part of the Bangladesh-China-India-Myanmar Economic Corridor, the Bangabandhu   Sheikh Mujibur Rahman Tunnel stands as a flagship project for the Belt and   Road Initiative, injecting new vitality into the economic development of   Bangladesh. CIECC will continue to forge ahead in collaboration with fellow   central state-owned enterprises, committing to higher quality joint efforts   in the Belt and Road, and contributing to a new and greater chapter of   friendly cooperation between China and Bangladesh.