China’s express railway network linking urban centers to far-flung corners of the country continues to expand at full speed. The nation that only started laying tracks for its first high-speed link in 2007 now boasts the world’s most extensive express rail network, stretching 29,000 kilometers as of the end of 2018.
No less than 4,000 km of new lines will be built this year, as China Railway Corp. aims to knit more trunk routes to serve key hubs and their sprawling conurbations in coastal areas in order to tap growing customer bases to fund the construction of feeder lines in central and western provinces.
The continued bonanza has seen a rising number of bridge and structural engineers joining the state-owned railway operator, needed to address the increasing trend of elevating bullet trains onto lengthy flyovers and bridges.
A chief engineer with China Railway Design Corp’s bridge department told the Beijing-based Economic Daily that China’s first 350 km/h high-speed rail line between Beijing and Tianjin, inaugurated in 2008, was virtually a rail route on bridges, as bridge sections accounted for almost 90% of its total length.
Bridges occupy much less land area than is required for ground-based rail routes. A ground-level railway route swallows 28.4 hectares of land per kilometer of track, while the same length of track on a bridge only takes up 10.9 ha of land, according to the expert. Thus, elevated rail routes can free up ground space in densely populated regions.
Bridge sections are pre-engineered and prefabricated in factories and then transported to construction sites to be bolted together. This speeds up construction and ensures better quality control.
The 1,318-km Beijing-Shanghai high-speed railway, which opened in 2011 to link China’s two largest cities, boasts the world’s longest bridge: the 164.8-km viaduct between Danyang and Kunshan near Shanghai spans four cities in eastern Jiangsu province, where the predominant terrain is made up of rice paddies, canals, lakes and swamps.
The bridge runs roughly parallel to the Yangtze River, passing through the northern edges of urban centers along the way. Employing over 10,000 workers, construction took four years and cost about US$8.5 billion, according to Xinhua.
The Beijing-Shanghai rail artery also features another mega viaduct near Tianjin in northern China, with a total length of 113.7km. The elevated track design was chosen to avoid thwarting the development of a number of industrial estates and other railways planned in close proximity to the high speed rail link.
The bridge consists of more than 3,500 steel and concrete girders, each 32 meters long and weighing 860 metric tons. They were brought to the installation sites and placed on piers by special cranes.