Study On Bond Performance Between Underwater Bottom Sealing Concrete And Steel Casing

At present,the academic and Engineering Research on the regularity of the bond performance between the bottom sealing concrete and steel casing is not deep enough.This paper relies on the research and development project of CCCC Second Navigation Engineering Bureau Co.,Ltd"Experimental Study on key parameters of platform support and cofferdam bottom sealing",the distribution law of bond stress between bottom sealing concrete and steel casing as well as the ultimate bond load and other performance indicators are explored through the test,and two factors（pouring environment and construction conditions of bottom sealing concrete）are mainly considered The influence of pipe diameter of steel casing on the bonding property is studied.According to the research method of"experimental research finite element verification theoretical analysis",thesis makes 10 test components of steel casing and sealing concrete bonding,and carries out pull-out test on them.Based on the correlation analysis,it puts forward the calculation formula of bonding force which can be used in engineering practice,and obtains the distribution formula of bonding stress along the bonding height through fitting,so as to provide reference for future engineering practice It can provide some reference and guidance.The main work and conclusions are as follows.1.Ten structural components bonded with steel casing and bottom sealing concrete were made,and the bond failure test was carried out.Two factors,the pouring environment of bottom sealing concrete and the diameter of steel casing,were set up to explore their influence on the distribution of bond load and bond stress along the bond height.2.Through the finite element software ABAQUS,the contact between the steel casing and the back cover concrete is simulated by the cohesive element.The properties of the cohesive contact element are determined by the test results.The finite element analysis results are extracted and compared with the test results to verify the bond distribution law based on the test results.3.Based on the test results,the test phenomena of pouring bottom sealing concrete under ordinary environmental conditions and underwater pouring bottom sealing concrete are similar,and the load displacement curve and bond stress distribution are similar.Therefore,it can be considered that pouring bottom sealing concrete under ordinary environmental conditions and underwater pouring bottom sealing concrete are mainly reflected in the difference of concrete strength in macroscopic,and the strength of bottom sealing concrete is straight The higher the concrete strength,the greater the bond strength between them.4.When other conditions are the same,there is a linear relationship between the pipe diameter of the steel casing and the ultimate bond load between them.Based on this,a simplified formula for calculating the bond load between the bottom sealing concrete and the steel casing is derived,and the bond coefficient K between them is obtained from the test and finite element analysis results.5.There is a maximum value of the bond stress along the height distribution,and the maximum value is close to the loading end.From the free end to the maximum value x_max,the bond stress is exponentially distributed,and from the maximum value x_max to the loading end,the bond stress is approximately linearly distributed.The calculation formula of the bond stress distribution along the height under the test condition is obtained by fitting.