AIZHAI BRIDGE MAP
Lushly green, shrouded in mist, studded with ravines, gorges, and waterfalls, the Aizhai Bridge’s setting has an otherworldly beauty. Minimizing the bridge’s impact on the natural environment and overcoming geologic conditions in high mountains presented a number of structural challenges. They were met with a series of innovations for a span suspended 984 feet (300 meters) over the breathtaking Dehang Canyon in Hunan Province.
Beyond its thrilling height, the Aizhai Bridge is highly regarded in the engineering industry because of the extreme ingenuity that met its epic construction demands. Its stiffened steel girder deck seems to float in the sky. In reality, it stretches between two different types of anchorages: a tunnel anchorage on the northern Chadong bank and a more conventional anchorage on the southern Jishou bank. The bridge incorporates a novel pylon-girder detached suspension structure, in which there is a large difference in the span between the main cable and the stiffening girder. New ways of analyzing the stability of the bridge’s combined system of pylon, anchorage, tunnel, and rock cliff were developed, as were novel means of transporting and erecting the stiffening girder under treacherous conditions. In the weird subset of the population utterly fascinated by bridges, Aizhai is the equivalent of an albino whale: rare, impressive and just asking for a good ride.
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The world’s longest tunnel-to-tunnel span, the Aizhai is a critical link along the G65 Baotou-Maoming Expressway, a 1,875-mile (3,017-kilometer) road, much of it still under construction. The route is but one example of new, burgeoning infrastructure in the high mountains of western China that has seen the construction of numerous long-span suspension bridges in the last decade. Suspended spans over steep terrain remain rare, however, because of the complex topographical and geological challenges that must be overcome, including constricted construction sites, extensive rock excavation, sharp slopes that adversely affect foundation stability, and ever-present safety hazards to workers.
Multiple exploratory techniques were used at various stages of the Aizhai’s design and construction to determine the site’s fitness. To give but one example, two adits, horizontal shafts, each more than 328 feet (100 meters) long, were bored into the Chadong bank. Testing inside the adits included electromagnetic-wave computed tomography, drilling scans, transient electromagnetics, and seismic surveys. For good measure, video cameras were also lowered into the holes. Additionally, ground-penetrating radar helped identify defects in the rock that surrounded the cable pylon and anchorage. A view of the bright red box girder that supports the deck of this technological wonder.
Not surprisingly, the bridge attracts extreme sports enthusiasts and adventurers of every stripe. Garden-variety rock climbers, hikers, and spelunkers all call in, but it’s not unusual to see paragliders soaring over the valley or BASE jumpers flying off the bridge. In fact, to celebrate its 2012 opening, more than forty BASE jumpers from thirteen countries took the leap, their daredevilry now commemorated on YouTube. For thrill seekers wanting the best of both worlds, there is a pedestrian crossing below the vehicular roadway, the floor of which is inset with glass panels.
One way of reaching the bridge is via the Aizhai Winding Road, a tourism magnet in its own right. Despite thirteen hairpin turns along steep, narrow roadways, it is almost always jammed with traffic.