China has built a new research facility to simulate an attack by nuclear bunker-busting weapons and learn how they damage defence facilities, even those built at extreme depths, according to military scientists involved in the project.

In the past, shelters buried several hundred metres deep were rated nuclear-proof but the Chinese test facility shows that a tunnel more than 2km (1.24 miles) under the surface could be destroyed, according to the researchers.

In one test, the simulated tunnel almost crumbled after taking hits the effective equivalent of five consecutive strikes by earth-penetrating nuclear weapons, an outcome that would have once been considered impossible.

The Cheyenne Mountain Complex at Peterson Air Force Base in Colorado Springs, Colorado. Photo: norad.mil

For instance, the Cheyenne Mountain Complex, home to the North American Aerospace Defence Command, was dubbed by the US military as the “most secure facility in the world” because it was protected by granite above more than 500 metres (1,600 feet) thick.

Openly available information suggests most ground-penetrating weapons could not reach a depth beyond 40 metres (130 feet).

But with the recent rapid development of technology, existing safety standards may be outdated and have “severely underestimated the actual impact” of nuclear weapons, said Li Jie, lead project scientist with the Army Engineering University of PLA in Nanjing, Jiangsu province, in a paper published in the peer-reviewed Chinese Journal of Rock Mechanics and Engineering last week.