Design And Optimization Of Steel Pipe Pile Cofferdam In Deep-water Bridge Of Dadu River

With the increasing of sea-crossing and river-crossing bridge in our country,the construction of bridge deep water foundation is inevitable.In order to guarantee the normal construction of pile caps,it is need to build a temporary cofferdam,which causes the cofferdam construction process in the dry state,so as to complete the excavation and building structures,etc.Steel pipe pile cofferdam used in deep foundation construction in our country start late,and its principle is to put the single pipe line by root into the water.The adjacent pile is stitched together to form a continuous structure which can block water and have certain strength.Steel pipe pile cofferdam has a rapid construction speed and large section rigidity,which can be applied to all kinds of complicated strata and has a wide application prospect.Based on the engineering background of 4# block of Dadu river bridge of chengkun railway,the paper studied the mechanism,bearing characteristics,failure characteristics and calculation method of steel pipe pile cofferdam,and carried out the following work:(1)The design and calculation of the retaining structure of steel pipe pile cofferdam are analysed by means by the analysis software of deep foundation pit.The cofferdam support scheme is determined,and the stability of soil depth calculation,steel pipe pile and cross section strength calculation,strength calculation,purlin strength checking,bottom sealing concrete strength checking and in design are completed.(2)Using MIDAS GTS finite element analysis software,the three-dimensional geometric is established for the cofferdam support scheme.Anumerial simulation analysis of steel pipe confferdam is carried out in each construction phase.And the distribution characteristics of the deformation rule of the steel pipe pile cofferdam,the stress of steel pipe pipe,the purlin stress and the stress of the steel pipe pile support are obtained under different working conditons.It also compares the calculation results of the Lizheng software and analyses the differences.(3)Optimize the design according to the analysis situation,optimize the cross section of steel pipe pile,and achieve good economic benefits through optimization design.The author thinks that three-dimensional finite element analysis software is more reasonable than two-dimensional foundation pit supporting software when designing and calculating cofferdam.In the design of foundation pit support,based on the two dimensional foundation pit support software,three-dimensional finite element analysis software is used to simulate the foundation pit to reduce the construction cost and increase the benefit.