Study On Application Technology Of Deep Water And Large Area Steel Sheet Pile Cofferdam

The steel sheet pile cofferdam has high strength and is easy to penetrate into the hard soil layer.It can be composed of various shapes as needed and can be reused many times.Therefore,the steel sheet pile cofferdam is widely used in engineering.In recent years,China has made great progress in the research and application of steel sheet pile cofferdams,but there are still many shortcomings,which limits the wide application of the structure to a certain extent.Based on the water intake cofferdam project of Ersheng Reservoir in Jurong City,this paper studies the design and construction of large-area double-row steel sheet pile cofferdam in deep water,including the analysis of the deformation of cofferdam structure under different precipitation conditions,double-row steel sheet piles.The front and rear rows of different connection methods are subjected to force deformation analysis and exploration of new connection forms,and the technical points of steel sheet pile cofferdam construction are systematically studied,which accumulate design and construction experience for similar projects in the later stage.The main contents are as follows:(1)Cofferdam structure design and analysis of force deformation under various precipitation conditions.Based on the example of cofferdam project,choose reasonable cofferdam structure form,optimize structural design and working condition,use MIDAS-GTS to establish three-dimensional finite element model of steel sheet pile cofferdam,and analyze the steel sheet pile cofferdam structure under various precipitation conditions.Force deformation characteristics.The results show that the pumping of water between the double-row piles can make the steel sheet piles more tightly engaged,achieve better water stopping effect and check the water-stopping effect of the steel sheet piles,and the deformation of the large-span double-row steel sheet pile cofferdams The force has obvious three-dimensional characteristics,and the lateral deformation near the middle of the cofferdam is the largest,and the deformation near the corner is minimal due to the arch angle effect.During the precipitation process,the deformation of the sheet piles in the mid-span of the cofferdam should be monitored.(2)The analysis of the different deformation modes of the front and rear rows of double-row steel sheet piles and the application of new connection forms.The front and rear row connection forms of double-row steel sheet pile cofferdams usually include steel welded joints and tie rod connections.It is proposed that the steel tie rods are connected in a new form to cope with the weakening of the steel support parts in the construction.MIDAS-CIVIL is used to establish the connection forms.The finite element calculation model is used to analyze the force deformation,and the weakening model of the steel connection is established at the same time.The results show that the steel support system has the largest stiffness and can provide a large support concentration.The combined connection is the second and the tie rod connection is the smallest.However,the combined connection provides greater support force than the steel support weakening state,and can provide support for the sheet pile at the same time.Tensile stress can better constrain the sheet pile offset.Therefore,the new connection form of the steel tie rod combination is worthy of popularization and application.(3)Construction points of steel sheet pile cofferdam structure and steel trestle construction platform and structural design research.Discuss the contents of pumping,seepage and rectification treatment of cofferdam structure,study the trawling bridge "fishing method" erection method,piling hole system and other issues,determine the appropriate construction plan,use MIDAS-CIVIL for the most important trawling bridge under different construction conditions Unfavorable load combinations are calculated.The results show that the strength,stiffness and stability of each member of the trestle bridge meet the requirements of the code and the structure design is reasonable.The on-site construction results show that the construction plan is reasonable,the cofferdam construction meets the expected requirements,and the trestle structure meets the requirements of construction vehicles and sheet pile insertion,which can be used as reference for similar sheet pile cofferdam projects in the future.