On July 26, 2021, the Chongqing Railway Hub Mingyuexia Yangtze River Bridge on the East Ring Road, designed by China Railway Second Institute and constructed by China Railway Second Bureau, was successfully closed, laying a solid foundation for the smooth opening of the entire line.

Introduction to the bridge

It is reported that Mingyuexia Yangtze River Bridge is located in Yuquan Village, Guangyang Town, Nan'an District, Chongqing City, on the upper reaches of the Yangtze River. It is the first double-layer four-track railway asymmetric vase-shaped steel truss cable-stayed bridge with a total length of 877.8 meters, of which the main span is 425 meters. , The upper level is reserved for the double-track high-speed railway (originally planned for the Da-Chongqing intercity railway), and the lower level is the double-line passenger and freight railway of Chongqing East Ring Line. The steel truss girder of the bridge adopts the N-shaped main truss structure and the orthotropic dense cross-beam deck system, with a total of 69 sections and a total weight of more than 26,000 tons.

The bridge is composed of two towers, two piers and two towers. The heights of the two towers are 189.5 meters and 203 meters respectively. The main tower and the steel truss beam are connected with 120 stay cables. The stay cables are arranged in asymmetrical space and double cable planes. The overall structure is novel, the technology is advanced, and the appearance is beautiful.

Overcoming difficulties

The bridge is located in the waters of the Mingyue Xiakou bend of the Yangtze River. The topography and geological conditions are extremely complex, with faults, broken zones, complex wind fields, maximum lateral flow velocity of 2.2 meters per second, and extremely high risk of ship hitting the bridge. Based on the wind tunnel test and wind-car-bridge coupled vibration analysis, the designer carried out the scientific research project "Research on the Key Technologies of the Four-Line Railway Cable-stayed Bridge in the Yangtze River Valley". The fan-shaped stay cables and wind-resistant bearings ensure the safety of construction and the comfort of the train after opening to traffic.

In order to solve the problem of deep-water foundation construction, the China Railway Second Bureau produced a huge steel cofferdam weighing more than 2,600 tons. The steel cofferdam was floated 117 kilometers from Fuling to the bridge site by barge, setting the record for the longest floating distance in the domestic inland river. In view of the problem of the extremely high risk of the water flowing through the clippers and the bridge collision, measures such as the establishment of navigation aids in the bridge area, core-filled concrete inside the lower tower column and self-floating steel-clad composite anti-collision facilities have reduced the risk of ship collision and made it possible The anti-ship collision performance of the lower tower structure reaches the highest level.

At the same time, as the first double-layer four-track railway asymmetric vase-shaped steel truss girder cable-stayed bridge in China, it also has a complex and super statically indeterminate structure, which makes it difficult to control the cable force and line shape; the steel girder assembly is complex and requires precision. High; the concrete pylon has complex structure, difficult construction, and high quality requirements; the bridge location crosses the main channel of the Yangtze River, and construction safety risk management requirements are high; the construction of the main tower foundation is greatly affected by the double influence of geology and water level.

In order to effectively resolve the construction difficulties and quickly advance the bridge construction, the project department took innovative technology as the core, and accumulated the "steel cofferdam water assembly construction method", "concrete high-pressure ground pump pipe fixing device", and "cable-stayed bridge tower pier top section steel". More than 60 authorized patents, high-quality construction methods and technical achievements of papers, such as the installation method of truss beams.

Technological innovation

In order to solve the problems of deep-water foundation construction, the project department adopted a double-wall steel cofferdam for auxiliary construction, and the steel cofferdam was launched into the water by the integral airbag method for water connection. At the same time, underwater ultrasonic terrain scanning was used on site to remove bedrock obstacles, realizing rapid and accurate positioning of steel cofferdams, and creating favorable conditions for subsequent pile foundation and cap construction.

In order to ensure the quality of the prestressed construction of the tower column, the project department innovatively used visual video equipment to penetrate into the pipeline to check whether the pipeline is damaged and accurately locate and repair it. It adopts a new intelligent tensioning and grouting system to monitor the entire tensioning process.

In order to simplify the measurement problem in the installation process of the stay cable, the project department innovatively adopted a steel strand meter counter to save precious time for the stay cable tension preparation. At the same time, invented a stay-cable construction method and a stay-cable construction device, which integrates the cable-laying cable during the tensioning process, and makes the tensioning process more efficient and controllable.

Relying on the Mingyuexia Yangtze River Bridge, the project department focuses on the application of BIM technology and establishes a project-level BIM application management platform. It realizes all-round application of BIM technology from many aspects such as model building, drawing check, construction simulation, progress control, safety management, material management and internal business management.

After the completion of the Chongqing East Ring Road, it will open up Chongqing’s urban airport, Longsheng, Tea Garden, Nanpeng and other areas to serve the transportation of enterprise goods and the travel of residents along the route. The layout is of great significance. Editor/Tian Zengpeng