The curious case of the fake island and the wandering blocks

China has come under fire from the international community for building up artificial islands in disputed parts of the South China Sea.

But it’s a Chinese-built island at home that has the city of Hong Kong in uproar.

What’s the problem?

A multibillion-dollar mega bridge linking Hong Kong to the neighboring cities of Macau and Zhuhai is sparking safety concerns.

Aerial photos of the Hong Kong-Zhuhai-Macau Bridge showed interlocking concrete blocks placed around the edges of an artificial island – which connects the bridge to a tunnel – appeared to have drifted away from the island.

The Hong Kong-Zhuhai-Macau Bridge Authority, which manages the project, has dismissed as unfounded any worries concerning the seemingly runaway blocks, which are known as dolosse.

A dolo-what now?

A dolos (plural dolosse) is a massive block of reinforced concrete. They are used in large numbers to absorb the impact of incoming waves, reducing erosion on landmasses.

Their geometrically complex shapes allow them to dissipate energy from waves and protect shorelines.

Over time, they tend to become increasingly interlocked with each other.

But the Hong Kong-Zhuhai-Macau Bridge Authority insisted that the blocks had been specially designed to be submerged in a “random manner.” 

It said that because the island was connected to a tunnel, a concentration of dolosse would exert too much pressure on the structure. 

But Hong Kong local experts were not convinced by the explanation, warning of a catastrophic risk if an undersea tunnel connected to the island was washed away because of insufficient protection.

What’s wrong with the picture?

Hong Kong structural engineer Ngai Hok-yan said he had reservations about the authority’s explanation, and questioned whether there was sufficient protection with just one layer of dolosse at the tunnel’s connection point.

 “Our standard practice is to use at least two layers of dolosse to serve as a protective zone,” he explained. “Also, each dolos used only weighs five [metric] tons compared with 25 tons each for those used [elsewhere]. It seems to me protection for the artificial island is insufficient.”

He warned of the effects of water if the island were insufficiently protected.

“The tunnel can be detached and float above the sea with cracks and water seepage. In that case, it will be game over for the tunnel and the bridge, too."

Veteran engineer Albert Lai Kwong-tak likewise called the authority’s explanations “unreasonable.”

He said the artificial island could have sunk.

 “It could be a problem of uneven settlement of the artificial island,” he added, noting that if that was the case, the tunnel could be at risk.

What’s the bridge for?

Hong Kong-Zhuhai-Macau Bridge is a project some eight years in the making.

The 34-mile series of bridges, artificial islands and tunnels forms a road link between three of the Pearl River Delta’s most important cities.

Intended to enhance economic integration and cooperation in the region, the bridge is expected to cut travel times by road between the cities from four hours to 45 minutes.

But the project has been plagued by at least two years of construction delays, and budget overruns on the main bridge of at least $1.5 billion.

The bridge is speculated to open in mid-2018 – as long as the island is still standing.