Study On Construction Risk And Anti-floating Stability Of Double Wall Steel Cofferdam

With the first successful use of double wall steel cofferdam in Jiujiang Yangtze River Bridge,because the double wall steel cofferdam has great advantages in the construction of deep water bridge foundation,double wall steel cofferdam technology has been widely used in the construction of deep water bridge foundation.However,due to the lack of double wall steel cofferdam related specifications,double wall steel cofferdam is usually designed by the construction organization,steel cofferdam design and construction of special programs most rely on the construction technicians based on experience,establishment level uneven due to design or construction is not standardized in recent years,the double wall steel cofferdam appeared a series of safety accidents in construction or the use of the process,resulting in significant loss of life and property.Based on the above situation,in 2015 “the double wall steel cofferdam design and construction safety technology”guidelines for research project by the Chongqing Municipal Transportation Commission approval,in 2016 the local standard “Chongqing double wall steel cofferdam design and construction safety technical regulations" project,In this paper,based on a bridge in Wanzhou,through the theoretical analysis,experimental research and finite element method of simulation analysis,this paper mainly made the following research work :1)Through the statistical analysis of a large number of double wall steel cofferdam,the reasonable structure form of double wall steel cofferdam is put forward;Collect and collate the relevant standard for the temporary structure of the permissible stress method and imited condition method,comparative analysis the difference of two kinds calculation method,for the design and calculation of double wall steel cofferdam,the permissible stress method can be adopted,And the permissible stress method is used to check the design of the double wall steel cofferdam;2)The construction risk of double wall steel cofferdam is analyzed by Fuzzy fault tree.It is found that welding seam penetration and the position deviation of the cofferdam and the quality of the bottoming concrete is the main risk factor,And puts forward the control measures of construction risk according to the main risk factors;3)Study on the influence factors of the overall anti-floating stability of the double wall steel cofferdam.It is found that the thickness of the bottoming concrete and the bond strength between the bottoming concrete and the steel casing have great influence on the anti floating stability of the cofferdam;Through experimental research,the bond strength between the Bottoming Concrete and the steel casing is proposed,The value is 0.17MPa;4)The anti-floating mechanism of double wall steel cofferdam is studied,and the safety factor of anti-floating stability of double wall steel cofferdam is put forward from the angle of safety and economy,and the safety factor is 1.15.