On October 27, the construction site of the Lugu Lake Grand Bridge on the Xixiang Expressway (Xichang-Shangri-La) witnessed a double celebration: the precise installation of the lower cross beam on the Shangri-La side was completed, while the cable support tower on the Xichang side surpassed the 100-meter height milestone. The megaproject, boasting multiple world records, achieved two critical milestones on the same day—"tower exceeding 100 meters" and "millimeter-precision closure"—marking the bridge's entry into a full-throttle construction phase.

The Xixiang Expressway represents Sichuan's largest highway construction project managed by a single project company in terms of investment and scale. It features nine megastructures, including the 1,952-meter Lugu Lake Grand Bridge—a single-span steel truss girder suspension bridge with a main span of 1,680 meters. The project also includes world-class engineering feats such as the Yuanbao Junction Underground Interchange (under construction), set to be the world's largest fully-underground interchange in a mountainous region, and the Litang River Grand Bridge, the world's longest towerless suspension bridge.

How is this highly challenging expressway being built with both speed and quality?

100-meter Cable Support Tower Achieved &Suspended Beams Perfectly Joined

The Lugu Lake Grand Bridge serves as a vital link between Xichang and Shangri-La, with the Yuanbao Junction Underground Interchange adjacent to it, where a branch road diverges from the main route toward Muli.

The site selection for the Lugu Lake Grand Bridge was exceptionally demanding, as it needed to accommodate both the linear layout of the expressway and integrate with branch interchanges. The bridge spans the Woluo River with a 500-meter vertical drop to the water. Its challenging location led to three world-record engineering solutions: the longest-span spatial cable suspension bridge, the longest-span steel truss girder suspension bridge in mountainous terrain, and the largest U-shaped tunnel anchor ever built.

Constructing such a suspension bridge begins with building the cable support tower on both banks—the foundational structures that bear the bridge's weight. Like two giants extending their arms to hold the main cables, these towers support the entire system. Countless suspenders are then anchored to these main cables, which in turn connect to the bridge deck, suspending it securely in mid-air.

On the construction site of the Lugu Lake Grand Bridge, the red cable support tower is steadily rising skyward. On October 27, the cable support tower at the Xichang side of the Lugu Lake Grand Bridge successfully surpassed the 100-meter mark, progressing steadily toward its final height of 228 meters. "The construction method for the cable tower is also a global innovation," said Li Peiyu, head of the Lugu Lake Representative Office for the Xixiang Expressway. He explained that the A-frame tower structure mimics the human body: steel tubes and boxes form the "skeleton", while concrete filling acts as "muscle". This integration leverages steel's tensile strength and concrete's compressive resistance, effectively addressing challenges such as strong winds, significant temperature variations, and complex geology in mountainous areas.

The same day, beam-lifting operations were underway on the Shangri-La side of the Lugu Lake Grand Bridge. The construction team utilized a "dual-safety visual aerial self-adjusting hoisting system", equipping the process with what functioned like "smart nerves" and "responsive joints". This allowed the beam to perceive its posture in real time during hoisting, make automatic fine-tunings, and remain steadily "suspended" in the predetermined position, achieving millimeter-level precision in the closure. The nearly 500-ton beam was assembled using a "zero-bracket" cantilever method in just 15 days, which cut the construction time by half compared to conventional techniques.

"Smart Hub" Boosts Project Pace as Over 80 Percent of Annual Investment Completed

Since its launch in 2022, the Xixiang Expressway has faced its most complex challenges in the "three bridges, five tunnels, and one interchange"—a series of megaprojects that represent both the critical difficulties along the route and key determinants of the overall construction timeline. The "three bridges" are the Lugu Lake Grand Bridge, Litang River Grand Bridge, and Yalong River Grand Bridge—all represent world-class engineering challenges. The "five tunnels"—Xichang, Yanyuan, Mianya, Muli, and Changbai—are all super long tunnels, each exceeding ten kilometers in length. The "one interchange" refers to the Yuanbao Junction Underground Interchange, where the design team broke new ground by relocating the entire interchange inside the mountain—a solution that cuts detour distance by 6.8 km and saves approximately 33 mu (about 2.2 hectares) of land. Li Xinwang, project manager for the Yuanbao Junction Underground Interchange on the Xixiang Expressway, explained that the construction employed nearly all known tunneling methods and techniques—utilizing 11 different excavation methods and 36 structural types—making it a veritable "museum of tunneling techniques".

"To accelerate construction progress, we have not only innovated in techniques and methods but also implemented smart systems across the entire project's construction management." Accompanied by a person in charge of the Sichuan Xixiang Expressway Construction &Development Co., Ltd., the reporter visited the project's dispatch and command center. This serves as the expressway's "smart hub", where construction progress is clearly displayed on large screens. Management staff can operate drones with a single click to monitor project status anytime, while AI assistants, laboratory modules, and other features support real-time synchronization of test data from all construction phases and enable traceability and control over non-compliant items.

Currently, all key control projects and highly difficult projects on the Xixiang Expressway have commenced construction. All 32 tunnels along the route are now under construction, and 128 of the planned 131 bridges have also broken ground. This year, the Xixiang Expressway project, with an annual investment plan of 11.5 billion yuan, has already completed 9.558 billion yuan, representing over 80 percent of the target. Several key projects, including the Lugu Lake Grand Bridge, have achieved critical milestones.

Looking across the province, Sichuan is advancing toward its annual goal of adding 900 kilometers of expressways, with a strategic focus on the "Three Prefectures" of Ganzi, Aba, and Liangshan. Under Sichuan's "Three Prefectures Network Densification" initiative aimed at expanding coverage and upgrading infrastructure, six expressway projects are set to be completed in the areas mentioned above within this year.