Study On Corrosion Characteristic And Effect Of Corrosion On Bearing Capacity Of Steel Foundation In Marine Geotechnical Environment

With the rapid development of ocean engineering,steel pile foundation,as the most common foundation form,has been widely developed and applied to support superstructure,which is faced with severe corrosion risk in the whole life cycle.It is of great practical significance to study the corrosion characteristics of steel pile foundation in marine geotechnical environment.At present,the study on marine corrosion mainly focuses on the corrosion loss of cross section and strength degradation of upper steel structures,but less attention is paid to the corrosion characteristics and bearing capacity of steel pile foundation in marine geotechnical environment.Therefore,aiming at the corrosion problems of steel pile foundation in marine geotechnical environment,combining accelerated corrosion test,interfacial shear test,theoretical model analysis method,discrete element and finite element numerical analysis method,a systematic and in-depth study on the corrosion characteristics and the influence of corrosion on the bearing performance of foundation is carried out.The main research contents include:1.Study on corrosion characteristics and surface topography of steel based on accelerated corrosion test.The electrolysis accelerated corrosion test of steel in marine geotechnical environment is carried out.The corrosion weight loss and electrochemical reaction process are analyzed.The corrosion depth and surface topography characteristics are analyzed by binocular laser scanning.The change law of surface roughness parameters with the corrosion degree and the probability distribution of rough surface height are emphatically studied.Based on the corrosion specimens obtained from the test,the surface morphology of corroded steel specimens is analyzed mathematically by using the stochastic process model.A stochastic reconstruction model of corrosion surface morphology with the degree of corrosion as the random variable is established.2.Experimental and numerical simulation study on shear behavior of corroded steel-soil interface.Based on the direct shear test of the corroded steel-soil interface and the discrete element model of interfacial shear,the stress deformation law and shear failure mechanism of the corroded steel-soil interface under unidirectional and cyclic shear are studied from macroscopic and mesoscopic aspects.The dynamic evolution process of interfacial shear particles is analyzed.The normalized formulas for the interface shear strength parameters,namely the interface cohesion and the interface friction coefficient,under different corrosion degrees are proposed.A hyperbolic shear constitutive model for the steel-soil interface considering the effect of corrosion is established.3.Numerical simulation of bearing characteristics of corroded steel pipe pile foundation.A finite element model of steel pipe pile foundation in marine geotechnical environment is established.Based on the contact surface constitutive model considering corrosion,the bearing capacity and displacement of steel pipe pile foundation under unidirectional horizontal,vertical and bending moment loads are studied.The change law of ultimate bearing capacity of steel pipe pile foundation is compared and analyzed when considering the reduction of wall thickness and the change of surface roughness of pile foundation due to corrosion and when only considering the reduction of wall thickness of foundation due to corrosion.The failure envelope of single pile foundation under V-H and V-M composite loading is obtained by Swipe loading method.The influence law of corrosion on the composite bearing capacity of steel pile foundation is revealed.