Mechanics Properties And Safety Evaluation Of Highway Bridge Pile In Alpine Salt Marshes

With the further development of China’s western development strategy,more and more Highway need to be built in complex and harsh environment.It requires that the abilities to resist all kinds of complex and harsh environment were provided to the Highway bridge pile foundation.However,in Alpine salt marshes there are high salinity surface water,groundwater,saline soil,wetting-drying cyclic,freezing and thawing,and drought climate conditions,which combined action formed unique composite salts and strong corrosive environment,and the formation of the composite salts of strong corrosive environment of highway bridge pile foundation,bearing capacity of the pile foundation of bridge will be threatened seriously,furtherly the structural safety of highway bridge will be threatened too.In addition,the bridge pile foundation is a concealment project,and it is difficult to detect the damage of the bridge pile foundation in the early,and which increases its harmfulness.The changes of mechanical properties of pile foundation of highway bridge in Alpine salt marshes were researched,and which safety was evaluated,based on field simulation test,indoor simulation test,theoretical analysis and finite element analysis,and according to Highway Traffic Science and Technology Project of Qinghai(2014-07),namely,“Prevention and controlling technology research on the corrosion of the bridge culvert infrastructure in the salt marshes of De-Xiang highway”,mainly reflected in the results:1.In this paper,based on site simulation test,the damage mechanisms of mechanical properties of the highway bridge pile in a range of certain pile depth below the ground were researched,under the action of wetting-drying cyclic,freezing and thawing cyclic in Alpine salt marshes,the microcosmic mechanisms of the highway bridge pile were proved,and recommended formulas of the damage mechanism of the highway bridge pile were proposed,and the optimal mix of concrete was selected in Alpine salt marshes,to provide a reference for the physical engineering in Alpine salt marshes corrosive environment.2.Based on indoor simulation experiments,the changes of long mechanical properties of the bridge pile were researched under the environment of long soaking,wetting-drying cyclic,maintenance of freezing and thawing,immersion of freezing and thawing,wetting-drying and freezing-thawing cyclic,and the long corrosion mechanisms of the bridge pile for above environment were ascertained.3.Based on the rough set theory,the important degree of six influence factors to the corrosion resistance coefficient and the dynamic modulus of elasticity of the bridge pile concrete which factors were long soaking,wetting-drying cyclic,maintenance of freezing and thawing,immersion of freezing and thawing,wetting-drying and freezing-thawing cyclic,and composite salt concentration.Based on the theory of damage mechanics,empirical formulas were put forward under the long soaking,wetting-drying cyclic,maintenance of freezing and thawing,immersion of freezing and thawing,wetting-drying and freezing-thawing cyclic,and to provide a reference for the determination of long mechanical properties of highway bridge pile foundation engineering in Alpine salt marshes.4.The degree of influence of the factors(ie,pile corrosion length,pile corrosion thickness,pile flaking thickness,the longitudinal reinforcement area loss rate of the pile)on the bearing capacity of highway bridge pile foundation was analyzed under the action of wetting-drying cyclic,freezing and thawing cyclic in Alpine salt marshes,.The pile corrosion length is the main factors which was put forward affecting ultimate bearing capacity of highway bridge pile foundation,reduction rate of the vertical ultimate bearing capacity of highway bridge pile foundation will be remarkable,as the pile corrosion length is above8 m.The pile flaking thickness is the main factors which was put forward affecting horizontal bearing capacity of highway bridge pile foundation,reduction rate of the horizontal ultimate bearing capacity of highway bridge pile foundation will be remarkable,as the pile flaking thickness is above 16 cm.5.A safety assessment model and risk evaluated model of the climate and environment on the bridge pile foundation in Alpine salt marshes were established,and which will provide a reference for the accurating evaluation of the damage degree and safety state on existing bridges in Alpine salt marshes.