The main section of the Beijiang Grand Bridge, a key project of the Qingxin-Huadu Expressway in Guangdong province, has been successfully linked, laying a solid foundation for its opening by the end of the year.

Construction of the 1,440-meter cross-river bridge, currently the largest four-tower, double-cable-stayed, two-way directional prestressed concrete girder bridge in China, began in October 2022.

Following 48 hours of continuous monitoring of elevation changes, tower cranes and mobile cranes extended their long arms as nearly 56 cubic meters of concrete were poured over a four-hour period in the early morning of May 20, culminating in the successful joining of the bridge.

After the operation, the bridge spanning the Beijiang River, a tributary of the Pearl River, began to take shape, showcasing its four cable towers shaped like phoenix tail feathers.

The project has faced an uphill battle due to complex geological conditions, according to Zhou Wei, director of the Qingxin-Huadu Expressway management office.

"The bridge site is characterized by extremely well-developed karst formations," Zhou said, adding that construction had to pass through multiple bead-like caverns. "Any slight misstep could lead to a cave-in or flooding."

The main piers consist of 120 piles with an average length exceeding 80 meters, with the longest reaching 102 meters, according to Zhou.

The project team implemented a one-plan-for-one-pile scheme for meticulous management, developing targeted pretreatment plans for the caverns.

"The scheme helped ensure a 100 percent success rate in achieving the required standards for the initial drilling of all 120 pile foundations for the main piers," Zhou said.

As all four main towers of the bridge are located in the water and are nearly 150 meters tall, alignment control has proved extremely difficult, with the structures affected by strong winds, floods and ship traffic, Zhou said.

"It's more like embroidering in mid-air at a height of 100 meters," he added.

High-tech platforms and intelligent systems were adopted during the bridge linking process, according to Xu Lu, project manager of the TJ3 section of the Qingxin-Huadu Expressway at China Railway Major Bridge Engineering Group.

"Linking the bridge was particularly challenging due to its considerable width of 37.6 meters," said Xu.

During the linking operation, a cable-stayed form traveler was used as a mobile working platform to pour concrete segment by segment. In addition, technologies including digital building information modeling, Beidou positioning, and comprehensive stress-strain monitoring systems were applied to continuously track bridge deck elevation and stay cable tension.

An intelligent closed-loop system integrating construction, monitoring, feedback and adjustment was also established, with more than 300 sensors embedded in the main beam to continuously monitor concrete stress, cable tension and temperature.

"We independently developed a universal tensioning and anchoring mechanism to fully adapt to the spatial position changes of the cable-stayed anchorage points," said Liu Wang, chief engineer of the expressway's TJ2 section project team at CCCC Road & Bridge International Co.

The expressway, approximately 54 kilometers long, starts in Qingxin district of Qingyuan, in the northern mountainous part of Guangdong, and ends in Tanbu township of Huadu district in Guangzhou, the provincial capital.

qiuquanlin@chinadaily.com.cn