Abstract: To find out the cause of the floating accident in Fengtaifengyi underground garage project，studies including analysis of the failure mode and on-site surveying are conducted. After the studies， such facts are thought to be the cause of the accident：1.Neglecting the seriousness of water influence， the constructors stopped dewatering too early；2.Backfilling work quality did not meet the requirement of design; 3. Neglecting the seriousness of water influence， supervisors did not function well in supervising the construction process; 4. Neglecting the seriousness of heavy rainfall，no effective measures were taken to drain water away; etc. This paper introduced the emergency measures taken to minimize the loss of life and property, and it also introduced the permanent reinforcement of the damaged structure. After the reinforcement, the structure went through a whole rain season and appeared to be in good condition, from what, we can think that the measures worked as expected, and achieved desired effect.

Key words: Single underground garage, Anti floating design, Failure mechanism, Emergency measures, Reinforcement