Road collapse ‘normal’ on reclaimed land

Tuesday, October 5, 2010
Issue 1131, Page 2
Word count: 680
Published in: Macau Daily Times

By Poyi (Natalie) Leung & Tiago Azevedo

Drivers, pedestrians and other road users perhaps need to be extra vigilant when driving or walking in Cotai or any other reclaimed areas in Macau, since the related Government departments have confirmed that natural subsidence could cause part of the roads to collapse at any time.

The roads in Cotai have been fixed on numerous occasions over the past few years due to uneven surfacing or uneven settlement of the ground. But in spite of the continuous effort to drive piles into the soil to reinforce the foundation support, it seems that the problem has persisted and may have even worsened.

In Avenida Marginal Flor de Lótus towards the Lotus Bridge and after the roundabout, five spots on the right beside the kerb have recently been found to have collapsed, with one of them just on the zebra crossing.

A hole measuring around 20 centimetres has also been discovered in the middle of the road.

The Civic and Municipal Affairs Bureau (IACM) has fenced off the damaged part of the road to warn drivers.

The same road was originally uneven before it was fixed just a few months ago.

On the right lane of the Sai Van Bridge heading towards Macau a crack stretching three to four metres long can also be observed.

While experts have said that it may be normal to see problems arising when building on reclaimed land, in Macau it seems it happens more regularly than usual.

The IACM media coordinator told the Macau Daily Times yesterday that the road collapse would have been caused by natural subsidence, which is “normal” on reclaimed land like Nape and the surrounding area of the Macau Dome.

Subsidence can occur owing to natural geological processing and continuous soil loading.

He said that while the surface of some parts of reclaimed land may shift downward at a faster pace, it is particularly “common” on roads and therefore maintenance needs to be carried out constantly.

He also admitted that the road may collapse again in the future even after it is fixed.

“It’s a natural condition and common among reclaimed land,” he told the MDT.

The media coordinator also said that the road and drainage department of the IACM examines road surfaces regularly and carries out immediate maintenance once a damaged road is found. However, Avenida Marginal Flor de Lótus has been in need of repair work for some time now, and aside from putting fences up, not much has been done in the past weeks.

According to Tiago Pereira, a civil engineer at the Macau Laboratory of Civil Engineering (LECM), Macau has a very thick mud bed, “that might vary from 15 to 25 metres”.

LECM’s mission is to provide the SAR Government and the civil construction firms, technical and technological support in the areas of civil engineering and related sciences.

“When this mud bed has to support a heavy load of sand, for us to build a reclaimed land, there is a lot of pressure, that forces the water out of the mud,” Pereira explained.

He continued: “In Macau, this thick bed is not water-tight, which means that it takes some time to leak the water from the mud. But there are ways to speed up the process, which makes it possible to slash the consolidation process from years to months.”

However, he added, “it is not possible to know precisely how many months, because it varies from one site to another”.

Meanwhile, the Land, Public Works and Transport Bureau also told the MDT that subsidence is “normal” in reclaimed areas, stressing that construction will only start on the surface after a period of time depending on the actual situation.

In response to the question of whether or not warnings should be issued to drivers and pedestrians in order to minimise the possibility of accidents, the Transport Bureau media coordinator said “it is difficult because we don’t know if the roads are going to collapse or not”.

She added that the most important thing is to inform the related department to fix the damaged road as soon as possible.

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