Shenzhen Yangang East Interchange Project to create a prefabricated bridge construction model

Walking into the bridge prefabricated construction site of the Shenzhen Yangang East Interchange Project of the Second Aviation Administration, the C and D ramp bridges that have been erected are connected into one section. The concrete surface is as smooth as a mirror, extending along the winding coastline of Dameisha towards Wutong Mountain.

New technology in prefabricated beams

Shenzhen Yangang East Interchange Project is located in the north of Donggang District, Yantian District. It intersects with Yanba Expressway, Pingyan Passage under construction, proposed Yanlong Avenue, and Jingang Road in Donggang District. Including 10 new ramps, including 16 bridges and 5 tunnels, with a bridge-to-tunnel ratio of 81%, it is one of the most complex interchanges in Shenzhen. Among them, the C1 and D2 ramp bridges have a total of 700 meters of straight sections as pilot prefabricated bridges. The prefabricated components include prefabricated pier columns and prefabricated segment beams. There are a total of 87 prefabricated pier columns and 233 segment beams.

As the first pilot project of prefabricated bridges in Shenzhen, none of the staff in the project department has had similar construction experience, but they can only do it while learning, and summarize and innovate while doing it. Prefabricated bridges have high requirements on the appearance of segmental beams and piers.

On December 13, 2019, project manager Du Xiurong led the management and technical team to Changsha Xiangfu Road project to learn segment beam prefabrication technology, and at the same time dispatched technicians to station in Zhongshan Prefabrication Plant to supervise production.

New challenges for transport

At the end of 2019, the project completed the prefabrication of all 87 piers and columns and 233 section beams, 3 months ahead of the original plan. But another problem is in front of the project: how to transport these prefabricated components from Zhongshan Prefabrication Factory to the construction site? The original plan was to transport by land. The prefabricated components were loaded from Zhongshan Cuiheng New District and arrived in Shenzhen via Guangzhou and Dongguan.

After investigation, Du Xiurong found that the east port area of Yantian Port, which is less than 3 kilometers away from the station, has good water conditions and is close to the world-class port - Shenzhen Yantian Port. Thousands of tons of transport ships can be docked smoothly, and the 400-ton crawler lifting beam can be used to land, and then the construction site can be reached by short-distance land transportation through the existing Donggang road.

After the project department communicated and coordinated with Yantian Port Group, they agreed to temporarily borrow a piece of land for the project to build a temporary wharf. But they encountered new troubles. It turned out that the land belonged to the area under construction of the breakwater project in the Donggang District of the Fourth Aviation Administration. If they borrowed it, they had to adjust the construction plan and leave a gap of 5 months. Under the coordination of the project department, the Fourth Airline Project Department agreed.

Next, the project department organized the team to work overtime, but a new problem came again. The temporary wharf is 14 meters long and 20 meters wide. According to regulations, it cannot invade the Shenzhen coastline in 2018. The draft of the transport barge is 2.1 meters, while the actual water depth is 0 to 3.5 meters. The project department used a long-arm excavator to clear 16,000 cubic meters of gravel in one month, but it still could not meet the needs. Considering that the temporary pier needs to be backfilled after use, it is obviously a stupid way to clean up the gravel afterward. The project department organized technical personnel to "brainstorm" and innovated "a pier structure with flexible docking piles at the upper and lower ports", which solved the difficult construction of rock strata, and the top and bottom of the front row were all flexible buffer structures. It can well dissipate the stress generated by impact or wind and waves, has good structural stability, has great promotion value, and has obtained a patent.

On March 26, 2020, the prefabricated components of the first ship went ashore successfully.

Second Aviation Manufacturing Boosts Quality Engineering

Compared with prefabrication and transportation of components, bigger challenges lie ahead. The Yangang East Interchange is located in the valley and low hills. The construction land is narrow and the terrain is complex. It is difficult for large machines to enter the site. Several ramps cross Dashuikeng River, Yanmei Road, Yansan Road, Pingyan Road A-ramp and its own bridges, and the construction organization is difficult.

As the first prefabricated prefabricated bridge project undertaken by the company, the project management team was faced with problems such as lack of construction experience and lack of technical personnel. Du Xiurong decided to go out to learn scriptures. After many inquiries, he learned that the connection method of the piers, columns and columns of the Chengpeng Viaduct under construction in Chengdu at that time adopted the same grouting sleeve dry connection method as the prefabricated assembly process of this project. 80 piers and columns have been successfully installed, accumulating rich experience.

On December 15, 2019, Du Xiurong led the project technical team to the Chengpeng Elevated Project to learn all the construction techniques for the installation of prefabricated piers. In the project planning stage, the Second Aviation Administration innovatively proposed the integrated installation process of piers and beams, and then independently developed an integrated bridge erection machine according to the actual situation of the project. The core equipment has been solved, and the control during the construction process is the key. The project department strictly controls the safety and quality, and adopts the whole-process adaptive geometric control method to cover the whole process of segment prefabrication and assembly. It takes a large database as the core, integrates calculation and prediction, error analysis and correction, correctly identifies and predicts the linear development trend, corrects construction errors, and optimally controls the state of the bridge structure.

During the construction of the segmental beam, the strength of the leveling layer between the pier top block and the support is relatively high. The project adopts C100 grouting material, and the water-material ratio is strictly controlled to be 0.12, otherwise the final strength will be affected. However, it is more difficult to stir the material, and it takes up to half an hour to reach the grouting requirement. During the construction of the top block of C1-5# pier, worker Wang Shengbao wanted to add more water when mixing the grouting material to facilitate mixing, but was stopped by the on-site technician. Then Wang Shengbao said: "Just add two or two more water, what effect will it have?" Sitting on the sidelines and giving up, the technicians strictly abide by the standards of the construction plan on the one hand, and educate and enlighten the workers on the other hand, to ensure the construction quality of the top blocks of the section beams and piers and the safety of the bridge erection machine. Before the bridge erection machine carried out the construction of the third span of the third span of the C1 ramp bridge, the on-site technician Su Kewei found that the top of the front outrigger and the bottom of the right bridge of Yanba Expressway would have a space crossing after the bridge erection machine had passed the span normally, which would affect the construction. Therefore, the project department organized the secondary optimization of the bridge erection machine, and chose to remove the main girder of the front span section by section during the spanning process of the bridge erection machine, so as to retain the length of the main girder required for the girder erection. By optimizing the construction plan, it is ensured that the construction nodes of the segmental beams are completed on time.

On July 10, 2022, the main body of the bridge of Shenzhen Yangang East Interchange Project was completed. Erhang people used their wisdom and strength to create an "assembly line" for bridge construction, which was recognized and honored in the pilot project of prefabricated bridge construction in Shenzhen. The project has successively won "Shenzhen Traffic Construction Model (Benchmark) Project", "Shenzhen Construction Engineering Safety Production and Civilized Construction Excellent Construction Site", "Guangdong Province SMART BIM Smart BIM Competition First Prize" and so on.