Chinese builders completed construction on the 832.2-meter-long Yuanjiang Super Railway Bridge, spanning the V-shaped Honghe River Canyon in Southwest China's Yunnan province.

It is the highest and longest-span railway bridge pier of its kind in the world, and showcases the smooth progress of the Chinese section of the 925.5-kilometer China-Laos railway, a major project in the Belt and Road Initiative.

The bridge was perfectly joined on Wednesday by builders from China Tiesiju Civil Engineering Group (CTCE) after a construction period of more than four years.

The dual-track bridge, located in Yuanjiang, Yuxi city, is one of 134 bridges to be built on the 508.5-km Chinese section of the railway, that will link Yuxi and the Lao capital Vientiane when fully operational in December 2021, said Kang Ning, publicity chief at CTCE Fifth Engineering Co Ltd.

The main span of the Yuanjiang bridge, with six piers in total, is 249 meters long while its No 3 pier is 154 meters high－about the height of a 54-story high-rise, said Liu Wei, deputy chief engineer at the First Civil Engineering Design and Research Institute under China Railway Eryuan Engineering Group.

The foundation of the No 3 pier reaches 78 meters underground, and took 22 months to build before official construction of the aboveground portion broke ground on Aug 20, 2018, Liu said.

Construction of the No 3 pier, which can withstand a maximum wind speed of more than 40 meters-per-second, was an engineering challenge and will help maintain safety and security going forward, he said.

"After many demonstrations, a construction scheme was proposed consisting of two reinforced concrete hollow piers to be connected horizontally by the pier top beam and the middle X-shaped steel structure. This first innovation mode of its kind in the country provides a Chinese plan for the construction of similar bridges with similar geological conditions in the future," Liu said.

Construction on the Chinese section, also called the Yuxi-Mohan Railway, began in April 2016 with an investment of 51.6 billion yuan ($7.3 billion), with 86.12 percent involving bridges and tunnels, joining the Mohan-Boten border crossing in northern Laos.

The 417-km-long Lao section, linking Mohan-Boten and Vientiane, has an operating speed of 160 km per hour with an investment of 37.4 billion yuan, said Ouyang Shi, chief engineer for the CTCE Yuxi-Mohan Railway project.

Li Pengcheng, manager of the project, said the railway will be vital for Laos in overcoming challenges in shifting from being "landlocked" to being "land-linked," lowering production costs and attracting more traders, investors and tourists to Laos.

As a demonstration project in China's "going global" strategy, the China-Laos railway is an achievement in Sino-Lao cooperation under the BRI, which aims to build a modern-day Silk Road connecting economies in Asia, Africa and Europe by land and by sea, he said.

China aims to build a 5,500-km Trans-Asia Railway, which begins in Yunnan's provincial capital Kunming and wends its way through Laos, Myanmar, Thailand, Vietnam, Cambodia and Malaysia before terminating in Singapore, Li said.

China and Thailand started building Thailand's first high-speed railway in December 2017, which will link with the China-Laos railway, he said.

Mou Ping, a 24-year-old builder from Guizhou province in Southwest China, said he has been working on the No 3 pier of the Yuanjiang railway bridge since March 2018, and the job has been challenging when working amid abundant rainfall, high temperatures, strong winds and even seismic activity.

"But now the two sections of the bridge are connected, and as a builder of this super bridge, I feel very proud. Also, I've earned a handsome income from it," he said.