IT IS WITH FIELD HOKKAIDO
Initiatives to Contribute to Achieving SDGs Fbe Coating Standards
Obayashi Corporation's relationship with Bangladesh dates back to the construction of the Shitalakhya Bridge, which was completed in 1977. Currently, Obayashi is working on the construction of a new railway bridge designed to improve the efficiency of the nation's transportation network. The project is not just about dealing with the raging Jamuna River, but also about tackling the challenge of constructing bridge piers with a special foundation structure that are designed specifically for railway bridges. There are only a few global examples of this method of construction even in Japan.
Rail container transportation has increased rapidly in Bangladesh in recent years as its own economy and that of neighboring countries has grown. Now people are demanding greater efficiency of the rail transport network. Having said that, much of the country's 2,877 kilometers of railway track was built under British rule before 1947, so the aged equipment and infrastructures was (and still is) in urgent need of replacement or reconstruction.
The existing Jamuna Multipurpose Bridge currently straddles the Jamuna River, which flows east-west through central Bangladesh. However, this existing combined road and rail bridge has only a single rail track with strict speed limits, which slows transportation and creates a logistical bottleneck. This major new project is designed to ensure smooth cargo transport and improve the efficiency of transportation networks between Bangladesh and its neighboring countries through the construction of a new dedicated dual track railway bridge upstream of the existing bridge. The project is divided into two zones, with Obayashi being tasked with construction on the east side.
Preparations to commence construction began in January 2020, but the outbreak of COVID-19 plunged several cities and regions into lockdown, delaying the start of construction until August of that year. To overcome the challenges presented by the pandemic, Obayashi had to employ a remote management system while local Bangladeshi joint venture staff proceeded with the on-site setup. This continued for roughly three months through to the end of October when Japanese staff were allowed to reenter the country. Historically, Obayashi had built strong bonds of trust with local staff and suppliers and subcontractors through past projects, (*1) and the fact that we were able to avoid delays in various processes was largely thanks to their efforts.
The Jamuna River is one of three major rivers in Bangladesh, with a width of 4.8 kilometers and a difference in water levels of about 8 meters between the rainy and dry seasons. Flooding occurs every year during the rainy season and the height of the riverbed can fluctuate roughly ±10 meters over the course of a year. When the river gets rough, the work barges can hit and damage the existing bridge, which carries gas pipelines and power lines. Any such incident could seriously impact the lives of local residents. We had to be extremely attentive to the weather and measure the water levels, current speeds, and the height of the riverbed on a daily basis to determine whether barge work could go ahead or not.
Furthermore, the Jamuna River boasts the world's fifth highest average flow rate at 20,000 cubic meters per second according to data taken near the construction site. That is in a completely different league to the 254 cubic meters per second flow rate of the Tone River in Eastern Japan, and the flow can result in heavy scouring of the riverbed. For this reason, the design of the bridge included a special bridge foundation structure despite the extreme difficulty in constructing it. There are very few examples even in Japan of the well foundation structure using steel pipe sheet piles with pile lengths of roughly 80 meters and high strength pipe junction. This is also the first time that Obayashi undertook such a construction.
Bridge foundation construction steps (cross section)
Right from the beginning, Project Director Takashi Kawasaki surmised that the key to carrying out the construction work to plan under such challenging construction conditions and within the contractual time constraints, would be to ensure the accurate piling of the steel pipe sheet piles for the main body of the foundation. The main point was to ensure the piles were driven in exactly verticaly. A device of measuring equipment called a transit was applied during the pile driving, and the tilt of the piles were checked all the way down their length.
Driving a pile of 79.2 meters in length exactly straight is no easy feat, so we first fixed 24 piles on the outer perimeter together with joints to form a circle. Then, additional piles were arranged in a cross shape and affixed inside the pile circle. If a pile does not remain exactly vertical, it cannot be properly driven in, and the inside of the cofferdam cannot be completely drained and become substantially watertight. According to Deputy Project Director Keiji Tominaga, who was in charge of on-site work, there was a lot of trial and error up until the third bridge pier. However, after identifying the problems and astutely adjusting the order of piling, the process proceeded smoothly from the fourth pier onward. A total of 27 bridge pier units were constructed.
Installation of the steel pipe sheet piles was completed on August 17, 2022, as scheduled. The project has now moved on to construction of the bridge pier substructure and the erection of the upper truss girders.
Large size of deformed rebars, which are D51 (main rebars: diameter of 5.1 cm) and D25 (hoops: diameter of 2.5 cm), are designed for the frame. In particular, the D51 rebar has hardly ever been used before in Bangladesh and local workers were not accustomed to handling such rebars that weighed around 16 kilograms per meter, so we expected considerable difficulties and incidents to occur during assembly. To reduce the amount of work conducted at height, we adopted the NOP carry method, which enables workers to assemble the hoops on the ground and insert and assemble multiple levels at once. A specialist technical supervisor was sent from Japan to offer technical guidance for this stage of the work.
Meanwhile, for the bridge pier construction scaffolding, which was over 20 meters in height, a completely systematized method of scaffolding was used. Scaffolding was custom-made to suit the specific site specifications and conditions, and ensure safety and workability during the process of the reinforcement bar assembling, the formwork assembling, and the concrete pouring. We also carefully explored the type of safety equipment required to prevent people or objects from falling, which has resulted in an accident-free work record to date.
Multi-level hoop rebars preassembled on the barge are suspended by crane and placed onto the already installed main rebars.
Thorough safety measures include installing site-specific custom-made scaffolding on the steel pipe sheet piles.
This project is being conducted as a Japanese ODA loan project, which supports the development of lower-income countries by lending development funds at lower interest rates and with long-term repayment terms. Mr. Kawasaki says that, while technology transfer is not the main objective of the project, "Japanese technology is being passed on to local workers and local site managers through suppliers and subcontractors. The key message that Obayashi should convey is organizational capabilities." He painstakingly educates local staff on organizational management, including safety and quality control, accounting, and document management.
"To work successfully in third world countries, you need strong organizational capabilities that can be developed by building solid ties with local staff, global staff, suppliers and subcontractors, and which gives you a firm foothold in those countries," explains Mr. Kawasaki. Singapore and Taiwan are important bases for Obayashi in Asia where we already possess such organizational prowess, and we would like to build up similar strengths in Bangladesh as well.
Overseas projects come with their own inherent thrills and rewards. You get a real sense of the sheer scale of the construction project. "If you want to be involved in large-scale construction projects, look outside Japan. A project of this size would be divided into about 10 construction zones and contracted to different companies if it were in Japan. You feel a great sense of satisfaction that you can't really experience in Japan," says Mr. Tominaga proudly.
Everyone in the Bangladeshi construction industry has heard of Obayashi Corporation thanks to the near daily media coverage of our previous project successes. When we met this client for the first time, they said they knew everything would be fine because they are working with Obayashi Corporation. This project is proceeding to plan despite the outbreak of COVID-19 during the construction period, and the client continues to express their trust in Obayashi Corporation.
According to Mr. Kawasaki, "It is important to complete the construction safely, build up greater trust, and leave people feeling they would like to ask Obayashi Corporation to do the next project as well. I hope the joint venture staff and suppliers and subcontractors feel they would like to work with Obayashi Corporation again, because that will help us secure the next project. We are committed to ensuring this construction project is a success."
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