660-tonne rock train used to reinforce railway bridge in flood-hit central Vietnam

By 5:00 pm on Monday, floodwaters had reached the bridge’s girder and continued to rise.

In response, Vietnam Railways (VNR) directed its units to move a 19-car freight train, each car carrying about 35 metric tons of rock, onto the bridge that evening.

At 7:00 pm, the train, weighing roughly 660 metric tons in total, was positioned firmly across the bridge.

Flood levels continued to rise, surpassing the bottom of the bridge’s girder by 12 centimeters on Monday evening.

VNR general director Hoang Gia Khanh told Tuoi Tre (Youth) newspaper that the strategy of parking a heavily loaded train on the bridge was aimed at countering the powerful forces of floodwaters and preventing the bridge spans from being lifted or displaced.

This is not the first time Vietnam’s railway sector has used such a measure.

From October 8 to 11, a six-car train carrying about 300 metric tons of ore was positioned on the Bac Giang railway bridge in Bac Ninh Province, northern Vietnam to stabilize it when floodwaters on the Thuong River rose to within 95 centimeters of the bridge’s girders.

During severe flooding caused by typhoon Yagi in September 2024, VNR prepared plans to deploy two stone-laden trains to reinforce the Duong and Long Bien bridges in Hanoi, though the measure was ultimately unnecessary as floodwaters subsided.

Historically, in 1971, when a stone-filled train was stationed on Hanoi’s Long Bien Bridge over the Red River to prevent it from being swept away during a major flood.

Why a heavy train can protect a bridge during flooding

Experts explain that parking a heavily loaded train on a bridge during major flooding increases the bridge’s overall weight, enhancing its stability against buoyant and lateral forces created by fast-moving floodwaters.

When floodwaters rise high enough to submerge bridge girders, two main forces threaten the structure: buoyant lift, which acts upward as water surrounds hollow sections, and horizontal drag, created by the water current hitting the bridge’s spans, piers, and structural members.

If the bridge is relatively light or its girders contain voids, these forces can cause the spans to shift, tilt, or even slide off their supports.

Therefore, positioning a train weighing hundreds of metric tons on the bridge significantly helps increase its static load, which enhances friction between the girders and their bearings while lowering the structure’s center of gravity.

The measure makes the bridge more stable and resistant to upward or lateral movement.