At 11:18 on March 9, 2022, the Lüzhijiang Bridge on the Yuxi–Chuxiong Expressway, designed by Guizhou Provincial Transportation Planning, Survey & Design Research Institute Co., Ltd., was successfully joined. The bridge has achieved three world firsts: it is the world’s longest single-tower suspension bridge with a span of 780 meters; it features the world’s largest tunnel anchor inclination angle of 54°; and it boasts the world’s highest lifting height for stiffening girders, at 320 meters.
The bridge is located at the border between Yimen County and Shuangbai County, spanning the Lüzhui River. The bridge has a total length of 798 meters, with a four-lane, two-way roadway, and a design speed of 100 kilometers per hour.
The bridge spans a typical, deeply incised “V”-shaped canyon. The terrain features continuous, rolling mountain ranges with steep and rugged topography. The bridge deck is situated at an elevation difference of 320 meters above the river surface, and also stands 320 meters above the summit on the Chuxiong side. On the Yuxi side, the average slope is about 40°, making it a steep terrain; on the Chuxiong side, the average slope is approximately 75°, approaching sheer cliffs.
The company’s team adopted several innovative designs to address the extreme asymmetry of the bridge site’s topography.
① A single-tower suspension bridge with an asymmetric structural design is adopted for the overall layout. The Chuxiong bank features steep terrain that makes it impossible to erect bridge towers. Therefore, the main cables pass through cable holes drilled into the sheer cliffs and are supported by roller-type composite cable saddles. From these roller-type composite cable saddles, the strands of the main cables are spread out and then anchored into the mountain body via tunnel anchors.
② The Chuxiong anchorage employs a roller-type combined cable saddle that integrates the functions of both main cable saddles and auxiliary cable saddles, enabling the main cables to change direction at the span division points and distribute the cables. It also bears the enormous vertical forces transmitted by the main cables. During operation, the roller assembly allows the saddle body to move freely in a horizontal plane, thereby achieving self-balancing of horizontal forces at the span division points.
③ The Chuxiong shore adopts a 200-meter construction cross-tunnel to assist in the excavation of tunnel anchors. From the outside, cable tunnels can be excavated; from the inside, anchor tunnels can be excavated, thus achieving zero-grade excavation for both cable tunnels and anchor tunnels.
④ The Chuxiong岸梁 structure connects to the continuous arch tunnel. Through structural modifications, the steel box girder following the end suspension cables is transformed from a single-box girder into two separate box girders that extend directly into the left and right tunnels without interfering with the central partition wall. The abutments of the split box-girder bridge are integrated into the secondary lining of the tunnel, eliminating the need for separate abutment structures.
