| Carbonaceous mudstone in southwest my country is widely distributed,with low strength,easy disintegration in contact with water,and fast weathering rate.There is excess humidity and heat in the southwestern region of my country,and the carbonaceous mudstone anchored slopes in this area are easily eroded by rainwater.During the infiltration process of rainwater,the free ions in the soil will dissolve and penetrate into the soil through the capillary pores in the cement slurry around the anchor.The surface layer of the anchor bar causes corrosion of the anchor rod and reduces the anchoring effect,thereby inducing the instability of the anchored slope,which seriously affects the safety of national property and the safety of people’s lives.In view of this,this paper relies on the National Science Foundation project "Study on the disaster mechanism,evaluation method and prevention and control measures of mudstone artificial slope under the coupled action of humidity,heat and force(51838001)".The corrosion cracking mechanism,the effect of titanate-silane coating on the corrosion resistance of bolts,and the stability analysis of carbonaceous mudstone anchored slopes were studied in depth.The main work carried out is as follows:(1)The carbonaceous mudstone corrosion solution is obtained by filtering the carbonaceous mudstone soil-water mixture to simulate the carbonaceous mudstone corrosion environment.The solution corrosion test,electrochemical test,SEM,XRD,FT-IR and Raman spectroscopy are used to study Corrosion law and mechanism of Q235 steel bar bolt,the results show that the low carbon steel bolt in the carbonaceous mudstone environment produces obvious electrochemical corrosion,the corrosion products are mainly concentrated on the anode surface of the test piece,and its color and area increase with time.Gradually deepen and increase;in addition,the corrosion rate per unit area shows an increasing trend with the increase of time,and can be divided into two stages of rapid increase(0-10 days)and slow increase(1030 days).In the early stage of corrosion,a monomolecular oxide film will form on the surface of carbon steel.As Fe ions on the surface of the steel body are oxidized,the oxide film is destroyed,and corrosion products are gradually accumulated.The entire reaction process is dominated by charge transfer and material transfer.The main corrosion products are α-FeOOH,γ-FeOOH,β-FeOOH,CaCO3,Fe3O4 and a small amount of FeSO4.(2)According to the specification "GB-T228-2002 Tensile Test Method for Metal Materials at Room Temperature",the slow strain stress corrosion test,electrochemical test and SEM test were carried out on the Q235 steel bolt specimen.The results show that:the carbonaceous mudstone simulates the liquid environment The stress corrosion sensitivity rate of the Q235 steel specimen in the middle is 1.2× 10-3mm/min,and its mechanical properties tend to decrease with the increase of temperature,and the stress corrosion sensitivity temperature is 40℃.The initiation and propagation of cracks occurred at the stage,and the corrosion product film will not hinder the progress of the corrosion reaction.The fracture mode of the specimen is a mixed fracture mode of plastic fracture and brittle fracture,in which plastic fracture is dominant,and its mechanical properties are reduced mainly.The influencing factors are the combined action of corrosion,stress and hydrogen,followed by hydrogen.(3)The titanate-silane coating was prepared on the surface of the Q235 steel sample,the solute ratio and preparation process of the coating were optimized by solution corrosion test,and the corrosion resistance of the coating was tested by SEM,EDS and polarization curve.The research results show that the optimal solute ratio of titanate-silane coating is 10vol%(Ti:Si=1:9),and the optimal preparation process is as follows:the particle size of sandpaper is 100 meshes,the immersion time is 20s,The drying temperature is 130℃ and the drying time is 12 minutes.The prepared coating is continuous,uniform and dense,which increases the selfcorrosion potential of Q235 steel by 0.551V and reduces the self-corrosion current density by 5.836×-6A/cm2.(4)The solution corrosion test and tensile test were carried out on the Q235 anchor bar,and the change law of its mechanical properties was studied.Geo-studio software was used to analyze the stability of the carbonaceous mudstone anchored slope.The conclusions are as follows:The slope stability coefficient decreases with the increase of corrosion time and corrosion medium concentration.One month before corrosion is a fast reaction period.The main influencing factors are corrosion time and corrosion medium concentration.After one month of corrosion,it is a slow reaction period.The main influencing factors For the concentration of corrosive medium,the anchor bars prepared with titanate-silane composite coating decreased by 4.5%and 10.1%in ultimate strength after corrosion for 5 months compared with those without coatings.The reduction in the coefficient of stability provided by the bolts was reduced by 6.8%. |
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