Forensic Geotechnical Analyses on the 2009 Building-Overturning Accident in Shanghai, China: Beyond Common Recognitions

摘要

To date, why a 13-story building in Shanghai fell abruptly to the ground in 2009 remains uncertain. By review of physical evidence, limit-equilibrium analyses, extensive calculations, and three-dimensional numerical simulations, this study reveals that the failure arose from a rainfall-triggered undrained general shear failure of the subgrade underneath the adjacent stockpile rather than previously identified lateral ground movement shearing off piles below the building or failure of piles along the excavation side incurring progressive tilting failure of the building. Deep-seated slip failure of the stockpile applied an impact load on the building and immediately produced an unallowable overturning moment around the south building edge; consequently, the building suddenly fell over southward. Furthermore, the following vital phenomena, which received no attention in the previous investigations, are also explored: (1) how this building fell over but an adjacent building subjected to similar conditions did not; (2) how this building supported by piles fell over but a flood wall supported by shallow foundation remained intact, although both were near a 10-m-high stockpile; and (3) how the flood wall near the 10-m-high stockpile remained intact but the flood wall near a 6-m-high stockpile underwent catastrophic failure. Finally, some design and construction issues involved in this failure case are discussed.