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  Reuters 9 Mar 07
S'pore tremors raise fear of building on reclaimed land
By Koh Gui Qing

SINGAPORE, March 9 (Reuters) - One Raffles Quay, the newest office block in Singapore's financial district, overlooks a vast swathe of reclaimed land on which a huge casino, a swanky apartment block and a new financial centre are rising up.

On Tuesday morning, as One Raffles Quay was swaying, rocked by a 6.3 magnitude earthquake in Sumatra, Indonesia, 420 km (260 miles) west of Singapore, some of its occupants could not help but wonder: how quake-resistant are buildings on reclaimed land?

Nearly 20 percent of land-scarce Singapore's surface area is reclaimed from the sea, and Singapore has scores of tower blocks, hotels, factories and petrochemical plants on reclaimed land. In the coming years the city-state will develop a second financial centre, all on reclaimed land in the Marina Bay area.

So, is it safe? Engineers say that because reclaimed land is created by dumping sand into bodies of water, buildings rock more violently during tremors, although that does not mean they are unstable.

"Reclaimed land is made up of sea sand, so buildings will be shaken up more violently during earthquakes as compared to those on non-reclaimed land, which is solid and will not be liquefied by the shake," said Fan Sau Cheong, an engineering professor at Singapore's Nanyang Technological University.

He told Reuters that buildings on reclaimed land may shake two to three times more than those on natural land during earthquakes because sand in reclaimed land slides like liquid when saturated with water, in a process called liquefaction.

On Tuesday, about 150 buildings in Singapore were rattled by the quake and hundreds of people in the financial district fled their offices. No buildings were damaged and nobody was hurt.

PANICKING

"Blinds were shaking and the secretaries started panicking," said an office worker at One Marina Boulevard, a tower block next to One Raffles Quay. "Then some people started saying 'Oh no! And we are on reclaimed land!' It's just this instinctive fear that there are more risks with reclaimed land," she told Reuters.

Singapore's Building and Construction Authority denied that buildings on reclaimed land are more vulnerable to tremors than those on natural land, citing strong building foundations that can withstand tremors from distant earthquakes.

Unlike buildings in earthquake-prone Japan and Taiwan, Singapore buildings are not designed to be quake-proof, as Singapore does not sit on any major geological fault lines.

But since quakes in Indonesia are often felt here, the joints connecting the columns in many tall buildings should be connected more flexibly, to allow them to better absorb tremors, Fan said.

To ensure that a plot of reclaimed land will be stable enough to hold buildings, Singapore lets the land lay fallow for about 20 years to allow the sand to settle.

Singapore is not the only country building on reclaimed land. Macau has reclaimed land to erect more casinos and hotels, while Dubai has spent hundreds of millions of dollars creating a palm-shaped resort island off the coast of the Gulf emirate.

Engineers say that reclaimed land is always prone to sinking due to the difficulties in compacting the sand and draining the water trapped inside the reclaimed plot, which causes reclaimed land to subside more easily.

Japan's Kansai International Airport, the world's first airport built on reclaimed land, has sunk more than 11.5 metres since construction began in 1987.

However, buildings on reclaimed land will not sink if they are supported by steel or concrete columns that are hammered all the way into the seabed, although the streets circling the buildings may sink alongside the drooping land, engineers say.

"The building will not be floating on reclaimed soil," said Lee Siew Eang, a building professor at the National University of Singapore.
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