VIENTIANE - The concrete casting for the last pier understructure of Luang Prabang railway bridge has been successfully completed, laying down all the foundation construction work of the two cross-Mekong River super major bridges along the China-Laos railway.

At Tuesday night over the Mekong River in Luang Prabang city's north, some 220 km north of Lao capital Vientiane, tankers were busily carrying concrete for the casting of No. 21 pier foundation of the bridge.

Tang Gaoyun, division secretary of the Communist Party of China working committee with the China Railway No.8 Engineering Group (CREC-8), responsible for the construction of the third section of the China-Laos Railway and the construction of the two cross-Mekong River railway bridges, told Xinhua on Wednesday that after building the No.21 pier foundation of the Luang Prabang railway bridge, his CREC-8 division has planted a major milestone along the China-Laos Railway, which means the completion of the main and the most difficult work of the two cross-Mekong River bridges' construction.

"We have passed through a critical juncture," Tang said. "The completion of the No. 21 pier foundation will pave the way for the CREC-8 to raise all the Mekong River bridges' piers above the flood level before the flood season."

As one of the key projects of the China-Laos Railway, the Luang Prabang cross-Mekong River super major bridge is 1458.9 meters long, with 34 spans. And the construction of No.21 pier is the most complicated and risky, due to its proximity to the main shipping lane in the middle of Mekong with deep water and strong current around.

The China-Laos railway crosses Mekong River twice on north of Luang Prabang, with the Luang Prabang bridge and Ban Ladhan bridge under construction.

In the other relevant development, the last pier foundation of the Ban Ladhan railway bridge over Mekong River, some 240 km north of Vientiane, has completed concrete casting on July 4, and the pier has risen above flood level last Sunday.

To some degree, construction of bridges and tunnels is the decisive factor of whether the China-Laos railway can be built on schedule. The China-Laos railway has a total length of more than 414 km comprising 60 percent of bridges and tunnels, linking Mohan-Boten border gate in northern Laos and the capital of Vientiane.

The China-Laos railway is being promoted by the leaders of the two countries as a project of interconnectivity. Since the commencement of construction in December 2016, the building of tunnels, bridges, roadbeds and other sections has progressed smoothly along the route.

The operating speed of trains on the route is designed to be 160 km per hour. The railway is expected to be fully operational in December 2021.