Untold story of building the cable-stayed bridge with the largest span in Vietnam

My Thuan 2 Bridge has been put into operation, helping people in the West to overcome the fear of traffic jams every Tet holiday. However, few people know that behind this large-scale project are tireless efforts to overcome difficulties and interesting stories in choosing design options.

Taking advantage of the rare free moments at the end of the year, holding the phone in hand to scroll through the news and images of the radiant faces of the people of the Western region traveling on the newly put into operation My Thuan 2 bridge, escaping the traffic jam on My Thuan 1 bridge every holiday and Tet, Mr. Tran Quoc Bao, Deputy General Director of Transport Design Consulting Corporation (TEDI) reminisced about the first days of "probing the way" and choosing the design plan for this special project.

Mr. Bao said: My Thuan 2 bridge was started to be researched around 2007 during the research process of My Thuan - Can Tho expressway project.

At that time, TEDI's assigned task was to find the starting point for the expressway, not to specifically study the investment plan for the My Thuan bridge.

"However, calculating the location for this vital bridge plays an important role. Determining where the bridge is located, "naming" the starting point of the My Thuan - Can Tho expressway will ensure optimization," said Mr. Bao.

The construction site of My Thuan 2 bridge during Lunar New Year 2023

TEDI leaders recalled: At that time, evaluating the groups of options going downstream of My Thuan bridge, the North cutting through the existing factory area, the South going into the Central Planning area of ​​Tan Ngai urban area, Vinh Long city and not suitable for the direction of Trung Luong - My Thuan - Can Tho expressway, the design studied 4 groups of options for the location of My Thuan 2 bridge going upstream.

Group 1 is 100 - 150m upstream from the current My Thuan bridge, far from the erosion hole location but close to the current My Thuan bridge and located in the planning area of ​​Vinh Long city.

Group 2 is 350 - 600m upstream from the current My Thuan bridge, outside and near the erosion hole location and outside the planning of Vinh Long city.

Group 3 is 1,100m upstream from the current My Thuan bridge in the direction of the approved planning route. This option is outside the planning of Vinh Long City but passes right through the middle of the deep erosion area.

Group 4, about 4,700m upstream from the current My Thuan bridge, is outside the planning of Vinh Long city, far from the wolf hole but also far from National Highway 1A, making it difficult to attract vehicles.

My Thuan 2 Bridge

The research and consulting process also determined that, according to the planning, this river section ensures the passage of ships with a load capacity of 5,000 - 10,000 DWT, the main span length must be determined based on the calculation of the navigation aperture to ensure at least 300m.

From there, the most suitable bridge options are proposed, including: arch bridge; cable-stayed bridge; suspension bridge.

After going through the process of "lifting up and putting down", the arch bridge option was assessed to ensure aesthetics, however, in the condition of very high clearance (37.5m), large water depth, weak geological conditions, main span length from 400m or more, it did not ensure economic and technical feasibility.

The suspension bridge type has the lowest dynamic stability, the foundation structure is not suitable in areas with weak soil layers with great depth, the construction cost is high, and the construction method is unfamiliar to Vietnamese contractors.

The cable-stayed bridge option with average dynamic stability is also the lowest cost among the proposed scenarios.

"To reduce construction investment costs and ensure safe operation, the design team recommended choosing route 2, 350m from the current My Thuan bridge, using a cable-stayed bridge structure with a span of 350m," Mr. Bao recalled.

Workers constructing My Thuan 2 Bridge Photo: Chi Hung

Over a cup of coffee, drop by drop, in a small alley in Hanoi on the eve of Tet, "eating in the human world, talking about the underworld" is a saying that a supervising engineer from TEDI (name withheld) repeated many times when recalling memories of the construction of Nhat Tan Bridge.

According to the engineer, due to the geological condition of the bridge construction area, there is a deep depth of weak soil, the layers are highly susceptible to landslides, the length of bored piles constructed has a diameter of up to 2.5m, and a depth of up to 110 - 114m.

"In the first 5 months, after 4 attempts, the pile construction was not successful. It was a very stressful time," said the engineer, adding: "I don't know how many meetings were held between the parties involved to determine the cause and find solutions."

Finally, all agreed to switch from reverse circulation to forward circulation drilling technology.

Workers stay at My Thuan 2 bridge construction site to work through Tet 2023

The construction of bored piles at My Thuan 2 bridge still goes through the following steps: drilling holes, cleaning holes, sliding steel cages, and pouring concrete.

The difficulty is that, if the piles are 1.5 - 2m in diameter and 60 - 70m deep, the drill rod does not have to extend too far, and control is still easy. However, with the bored piles of My Thuan 2 bridge, the borehole is deep, the drill rod has to be pulled out in many layers, the core becomes smaller and weaker.

"To ensure safety in conditions of great depth, drilling holes must be done little by little, which we often call "earwax removal".

In addition, if constructing conventional piles, the weight of each steel cage brought down only weighs a few dozen tons, the concrete volume is only up to 100m3, but at My Thuan 2 bridge, the steel cages brought down weigh more than 100 tons with the concrete volume of each pile more than 700m3. Without experience, technical problems can occur at any time," said the consulting engineer.

My Thuan 2 Bridge is located parallel to the existing My Thuan Bridge.

Wrapping up 3 years of working on the My Thuan 2 Bridge project, Mr. Nguyen Tien Thanh, Deputy General Director of Trung Chinh Trading and Construction Company Limited, also had time to keep many beautiful memories.

As the unit in charge of constructing tower pier T15 (one of the two main towers of the project), anchor pier T14 and 1/2 of the main cable-stayed girder on the Tien Giang side, Mr. Thanh said that the biggest challenge in solving the progress problem at My Thuan 2 bridge is that the contractor cannot increase the construction site like the road construction because it cannot increase the number of casting trucks and install two anchor formwork at the same time.

Special construction conditions require contractors to meet three factors: progress, quality, and safety so that the implementation process is not interrupted. Before each item, contractors must meet to point out possible risks.

According to the leader of Trung Chinh Company, the work of controlling geometric dimensions is also considered the most successful at My Thuan 2 Bridge.

To ensure the geometric dimensions are in accordance with the design, the two main span contractors, Trung Chinh and Trung Nam, have coordinated according to an absolutely balanced plan. That is, the construction sequence, construction load and construction progress are all similar.

"Thanks to the synchronous participation and precision in construction, My Thuan 2 Bridge has achieved the miracle of constructing the remaining items within the time from the main span closing to the completion time.

My Thuan 2 Bridge has a total cost of more than 5,000 billion VND>

The construction of items: cable tensioning, internal force adjustment, bridge deck construction, railings, lighting, road markings were completed in less than 3 months. This is almost a new record in cable-stayed bridge construction in Vietnam.

Without careful calculation and day and night work, the implementation time of the above items will take no less than 5 months.

As for Trung Chinh Company's work, according to the signed contract, the construction time is 26 months, but the actual total time is only 24 months," Mr. Thanh shared.

Referring to the achievements of the My Thuan 2 bridge project, the leaders of Trung Chinh Company also did not mention the return of the "old people".

"Mr. Tung, Mr. Nhu, Mr. Cuong...> These are the first Vietnamese workers trained by foreign contractors to build My Thuan 1 bridge.

After that, they continued to participate in the construction of several other large bridges and then returned to their hometowns to live. When the My Thuan 2 Bridge was deployed, through an introduction, they applied again and carried their backpacks to the construction site to contribute, even though they were over 50 years old," said Mr. Thanh.

Permanently directing the construction at the site, Deputy General Director of Trung Chinh Company Nguyen Tien Thanh also did not forget the construction time of K0 dismantling and installing the casting car.

Mr. Thanh said: In the construction of a cable-stayed bridge, the construction phase of these items is the most difficult when the contractor has to dismantle 1,000 tons of K0 scaffolding (the first block of the girder), install two sets of casting trucks weighing 250 tons/set, and construct the first cable. The work is carried out simultaneously and falls right on the occasion of Tet 2023.

"At that time, everyone had decided to be away from home for Tet and focus on the construction site. Amidst many worries, the biggest consolation was that the project received special attention from the Prime Minister.

Encouraging engineers and workers to stay on site during Tet, the Prime Minister asked leaders of Vinh Long province to take care of Tet for workers.

The construction teams of My Thuan 2 Bridge and My Thuan - Can Tho Expressway were awarded 4 pigs by the province. Fresh pork was processed and divided among each team.

Everyone was excited and determined to work on the construction as usual," Mr. Thanh said.

My Thuan 2 Bridge is a project built entirely by the hands and minds of Vietnamese engineers and workers.

Source: https://www.baogiaothong.vn/chuyen-chua-ke-lam-cau-day-vang-co-khau-do-lon-nhat-viet-nam-192240209165948423.htm