Nicoll Highway collapse
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The Nicoll Highway collapse was a construction accident that occurred at approximately 3:30 p.m. Singapore Time (UTC+8:00) on 20 April 2004 in Singapore when a tunnel being constructed for use by MRT trains collapsed. The tunnel was part of the construction of the underground Circle MRT Line, near the Nicoll Highway MRT Station. The supporting structure for the deep excavation work failed, resulting in a 30-metre (100 foot) deep cave-in that spread across six lanes of Nicoll Highway. The collapse killed four people and injured three. The accident has delayed the construction end date for the MRT station.
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[edit] Accident Causes
Recent investigations by the MIT show that the main reason of the suddenly collapse was the misinterpretated local geology and overestimatated soil shear strength in its analysis. The structure was therefore underdesigned to resist lateral earth pressures, on clay with very poorly features.
From the structural point of view, was observed also errors in detailing the structural connections for the structural bracing system; the collapse then occurred when the lower level of bracing was overloaded and there was inadequate capacity to redistribute the loads among the remaining supports. Although large wall deflections occurred during the excavation, the measured strut loads were smaller than expected. As a result, the project engineers were apparently unaware of the potential for a catastrophic failure, showing the importance of a good planning and design stages in great social projects.
[edit] Consequences of the collapse
The accident left a collapse zone 150 m (490 feet) wide, 100 m (330 feet) long, and 30 m (100 feet) deep. Four workers were killed, with three more injured also twisted steel beams, swallowed two construction cranes and knocked out a substantial chunk of the main highway running over the tunnel.
The rescue efforts were called off on April 23, 2004 because of the low chance of survival by that point, as well as danger to the rescue teams. There was also the increasing need to stabilize the ground around the accident site to reduce the risk of further collapses. All six lanes of the Nicoll Highway were heavily damaged, rendering the road unusable. The highway re-opened on December 4, 2004 after reconstruction efforts.
A committee of inquiry found main contractor Nishimatsu Construction Company and its officers as well as Land Transport Authority officers responsible for the collapse. Several other officers and subcontractors were reprimanded and issued warnings in connection with the accident. As a result of this accident, the first phase of the Circle line will be completed in 2010 instead. The affected station has been shifted about 100 metres (330 feet) away from the accident site.
[edit] The victims
- Vadivil s/o Nadeson, crane operator
A Malaysian of Indian descent, his body was the first to be recovered. The 44-year-old had reportedly tried to escape by jumping out from his crane when the incident occurred. He was found caught between a pick-up truck and a container.
- Liu Rong Quan (Chinese: 刘荣权), construction worker
The body of the 36-year-old Chinese national from Jiangsu province was found wedged between the wheel and chassis of a 10-tonne truck. Liu had started working at the site just ten days before the incident. He left behind a wife and daughter.
- John Tan Lock Yong (Chinese: 陈陆勇), Land Transport Authority engineer
The third victim to be found, Tan was due to finish his contract with LTA at the end of 2004 and had planned to migrate to Australia or New Zealand then. He leaves behind his wife, a grown-up daughter and a son.
- Heng Yeow Peow (Chinese: 王耀标), foreman
The body of the 40-year-old Singaporean was never recovered. According to survivor accounts, Heng had selflessly hurried his workers to safety but was himself trapped when the collapse occurred. Heng left behind his wife, two young children, his 70-year-old mother and nine siblings.
[edit] Criminal trials
Four men are facing criminal charges in the wake of the Nicoll Highway Collapse.
The first man being put on trial is Ng Seng Yoong who is a former project director of the Circle MRT Line who also monitored the excavation and design work in his other capacity as the Qualified Person on the site. He faces one charge of breaching conditions under the Building Control Act. Arguments were made that readings of instruments on site have indicated that things were not going as planned, but the warnings were not acted upon. On November 24, 2005, Ng was fined $8,000 (SGD) by the court.
[edit] References
- ^ "IAP class probes Singapore highway collapse", MIT news, 1 February 2008.
- ^ "First of Nicoll Highway criminal trials gets underway", Channel NewsAsia, 3 October 2005.
- ^ "Ex-LTA project director fined over Nicoll Highway accident", Channel NewsAsia, 24 November 2005.
[edit] External links
- Special report — Channel NewsAsia
- Nicoll Highway collapse — Singapore Civil Defence Force
- Nicoll Highway Collapse - Singapore Infopedia
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