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Another building shifted at ill-fated city complex
By Dong Zhen |
July 4, 2009, Saturday
|
Print Edition
Print Edition
THE construction mistakes that caused a 13-story apartment house to topple last Saturday also undermined a second building, causing it to shift slightly, an investigation team told reporters yesterday in Shanghai.
That building has been shored up, and nine others in the nearly completed Lotus Riverside development in Minhang District were declared to be stable, the team, made up of 14 architectural and engineering experts, said as it released its conclusions on what caused the fatal collapse.
The group's main finding was that the apartment building toppled because the builders ignored common excavation and earth-moving practices and carried out their work in a reckless fashion. There was no evidence that any of the building's structural elements were unsound.
"All 14 of us were extremely shocked by the sight that greeted us when we arrived on the scene the day of the collapse," Jiang Huancheng, a member of the Chinese Academy of Engineering and leader of the investigative team, said yesterday.
"Throughout my 46-year career in this field, I have never witnessed or heard of such a building collapse," said Jiang, who was also the designer of Shanghai's landmark Oriental Pearl Tower.
The team's conclusions confirmed earlier reports that the accident scenario began with the excavation of a multi-level underground garage at Building No. 7 in Lotus Riverside.
The earth removed from the garage area had been piled up near the building to a height of 10 meters, without any temporary containment structure.
Investigators determined that the mountain of silt, built up over six days of digging, was exerting 11 to 12 tons of pressure per square meter on the ground, nearly twice the appropriate weight limit.
Simply put, the building toppled because of the garage void on one side and the tremendous pressure on the other.
The first signs of trouble occurred on June 26, when a flood wall along the nearby Dianpu River began cracking. During heavy rain the next morning, the building toppled nearly intact onto its side in a slow-moving tilt that probably lasted five to 10 seconds, the investigators said.
A worker who was inside at the time was killed.
The complex was built on riverside silt near an ancient riverbed, but the experts said the collapse was not related to geological conditions.
Gu Guorong, a member of the investigation panel and a geotechnical expert, said yesterday that nearly 30 percent of the city's land area lies above old riverbeds. Construction in these areas is safe, provided the proper foundations are used, the experts said.
Foundation piles were inserted 33 meters deep under the No. 7 building. Experts said both the depth and construction materials used in the piles were proper.
They also pointed out that the nearby No. 6 building shifted 29 millimeters as a result of the garage excavation and piled-up earth.
Since the collapse, the garage area has been filled in and the dirt mountain removed. As a result, the No. 6 building was restored to an upright position.
Though the Lotus Riverside buildings have been declared stable, they will continue to be monitored, and further checks will be done to ensure their structural integrity.
"A state of stability is not equivalent to safety, however," Huang Rong, director of the Shanghai Construction Commission, said yesterday.
It wasn't clear when, or if, residents will be allowed to move in to the complex. The original schedule called for Lotus Riverside to be open for residency by the end of the year.
City government said yesterday that officials will hold a meeting with the 400-plus buyers in the apartment complex to discuss compensation.
Also yesterday, the Shanghai Construction Commission said it will begin a citywide inspection of all buildings that are now under construction. Inspection teams will be focusing on earth-handling practices in geologically vulnerable sites.
That building has been shored up, and nine others in the nearly completed Lotus Riverside development in Minhang District were declared to be stable, the team, made up of 14 architectural and engineering experts, said as it released its conclusions on what caused the fatal collapse.
The group's main finding was that the apartment building toppled because the builders ignored common excavation and earth-moving practices and carried out their work in a reckless fashion. There was no evidence that any of the building's structural elements were unsound.
"All 14 of us were extremely shocked by the sight that greeted us when we arrived on the scene the day of the collapse," Jiang Huancheng, a member of the Chinese Academy of Engineering and leader of the investigative team, said yesterday.
"Throughout my 46-year career in this field, I have never witnessed or heard of such a building collapse," said Jiang, who was also the designer of Shanghai's landmark Oriental Pearl Tower.
The team's conclusions confirmed earlier reports that the accident scenario began with the excavation of a multi-level underground garage at Building No. 7 in Lotus Riverside.
The earth removed from the garage area had been piled up near the building to a height of 10 meters, without any temporary containment structure.
Investigators determined that the mountain of silt, built up over six days of digging, was exerting 11 to 12 tons of pressure per square meter on the ground, nearly twice the appropriate weight limit.
Simply put, the building toppled because of the garage void on one side and the tremendous pressure on the other.
The first signs of trouble occurred on June 26, when a flood wall along the nearby Dianpu River began cracking. During heavy rain the next morning, the building toppled nearly intact onto its side in a slow-moving tilt that probably lasted five to 10 seconds, the investigators said.
A worker who was inside at the time was killed.
The complex was built on riverside silt near an ancient riverbed, but the experts said the collapse was not related to geological conditions.
Gu Guorong, a member of the investigation panel and a geotechnical expert, said yesterday that nearly 30 percent of the city's land area lies above old riverbeds. Construction in these areas is safe, provided the proper foundations are used, the experts said.
Foundation piles were inserted 33 meters deep under the No. 7 building. Experts said both the depth and construction materials used in the piles were proper.
They also pointed out that the nearby No. 6 building shifted 29 millimeters as a result of the garage excavation and piled-up earth.
Since the collapse, the garage area has been filled in and the dirt mountain removed. As a result, the No. 6 building was restored to an upright position.
Though the Lotus Riverside buildings have been declared stable, they will continue to be monitored, and further checks will be done to ensure their structural integrity.
"A state of stability is not equivalent to safety, however," Huang Rong, director of the Shanghai Construction Commission, said yesterday.
It wasn't clear when, or if, residents will be allowed to move in to the complex. The original schedule called for Lotus Riverside to be open for residency by the end of the year.
City government said yesterday that officials will hold a meeting with the 400-plus buyers in the apartment complex to discuss compensation.
Also yesterday, the Shanghai Construction Commission said it will begin a citywide inspection of all buildings that are now under construction. Inspection teams will be focusing on earth-handling practices in geologically vulnerable sites.
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