Erosion Test Reserarch On Wharf Steel-structure Coating In Inland River

Construction of large wharf in the upper reaches of the Changjiang River,including Chongqing,Sichuan Province,Guizhou Province,due to the existence of shallow covering layer and deep water construction problems,the lower part of the wharf is mainly used in the type of steel pipe concrete,both pile foundation and crossbar are widely used in steel structure.At present,the steel components of inland river port adopt coating protection method,which is mainly based on the anti-corrosion standard of coastal steel structure.In fact,the corrosion-resistant coating has been washed off after one year,which causes the corrosion of steel components to be serious.The main reason for this problem is the serious erosion of the corrosion-resistant coating by the sediment flow in the large flow velocity of the river.In this paper,the surface erosion characteristics of steel component coatings and the bonding strength properties of the coating-steel interface under the condition of sediment-laden flow are studied by physical model tests,and the erosion model of steel component coating suitable for river sediment flow is proposed.The main research work and the results are as follows:Firstly,Based on the anti-corrosion engineering of steel components in the port of Chongqing Orchard,the erosion test of model steel members with different erosion velocities under two groups of low sediment content and high sediment content was carried out on the basis of the analysis of the erosion environment of the sediment-laden water flow in the inland rivers.The results show that the erosion of the sediment-laden water flow on the steel component coating is mainly manifested in two ways,On the one hand,it is the repeated action of sediment particles,which causes the cumulative and micro-crack initiation and expansion of the coating surface.On the other hand,the corrosive medium penetrates into the coating-steel interface through the damage crack,weakens the interfacial bonding strength,and produces the corrosion reaction,which causes the coating to blister and flake.Secondly,the surface damage regularity of the coating under the conditions of different velocity,punching angle and erosion period is analyzed.The results of analysis shows that the erosion rate of coating is obvious with time,and its erosion process can be divided into three stages,such as slow increase,acceleration and deceleration,and the trend of erosion rate of coating is more gentle when velocity is low.With the increase of flow velocity,the maximum erosion rate of the coating is shifted from the 30 angle to the 45 angle,and the overall present trend is "middle big,small on both sides".Thirdly,The damage mechanism of coating surface was revealed based on the change of coating damage morphology under different erosion conditions.In the process of erosion,the impact of the sediment particles on the surface of the coating is mainly caused by the oblique punching angle,and the force can be decomposed into positive impact stress and horizontal shear stress.The former mainly causes the point pit type damage,the latter mainly forms the micro-cutting or the plough-cut damage.The surface damage of the coating showed two mechanisms of particle wear and fatigue damage.Fourthly,the weakening law of coating-steel interfacial bonding strength under different erosion conditions was analyzed.The results show that the weakening process of coating adhesion is affected by the erosion degree of the coating surface and presents the change of "slow-accelerating-slowing" three stages.With the increase of flow velocity,the decrease trend of coating adhesion is more obvious,and the maximum decrease value is shifted from 0°to 45°.Fifthly,Based on the experimental results and the existing theoretical formulas,the erosion model of the coating under the condition of large velocity sediment flow is proposed.The results show that the critical punching angle of the coating is about 40°,and its deformation erosion coefficient is more sensitive to the change of the flow velocity than the cutting erosion coefficient.At the same time,the cutting component and the total erosion amount are similar to the change trend of the punching angle,and the critical punching angle increases to the maximum value,and the deformation component increases linearly with the punching angle.