Study On Hydrogen-Induced Fracture And Damage Law Of Anchor Cable Under Deep Stress Corrosion Coupling Condition

As the carrier of binding force of surrounding rock in deep excavation,the coupling effect of tensile force,shear force and deep multi-attribute corrosion environment on prestressed anchorage structure during its service are the main reasons for the damage and fracture of anchorage materials.The failure of anchorage structures will further lead to the instability of surrounding rock in excavation,resulting in catastrophic accidents.The related studies shows that hydrogen-induced fracture is one of the main failure mechanisms leading to stress corrosion fracture of anchoring materials,and the cleavage characteristics of fracture surface show that hydrogen plays a dominant role in material fracture.The hydrogen diffusion and aggregation behaviors are the main factor leading to hydrogen induced cracking.To study the characteristics of hydrogen diffusion and aggregation and their impact on stress corrosion failure of anchoring materials,this thesis adopted indoor accelerated stress corrosion test and finite element numerical simulation method.Combined with material diffusion theory and hydrogen induced lattice expansion effects,the influences of coupling effects of stress intensity and hydrogen on stress corrosion cracking of anchor cable are analyzed in detail,and the microscopic mechanism of material fracture damage is explained.Through the laboratory accelerated stress corrosion cracking test,the underground rock and soil stress conditions of anchor cable used for underground support were simulated,and the influence of environmental factors on the cable cracking were studied.The results indicated that sulfide was an important factor for the occurrence of stress corrosion cracking of anchor cable samples,while the p H and applied stress level had direct impacts on the occurrence of stress corrosion cracking.On the basis of the experimental results,the diffusion process of hydrogen generated by electrochemical corrosion reaction in corrosion solution in prestressed anchor cable was simulated by using Comsol Multiphysics.The diffusion law,concentration and distribution of hydrogen atoms in the macro interior of anchor cable materials under stress environment were qualitatively studied.The results suggested that hydrogen diffusion flux was positively correlated with the hydrostatic stress gradient,which leaded to higher activity of hydrogen in the metal stress concentration,as well as promoted hydrogen diffusion and accumulation to the high stress area.In addition,according to the action form of hydrogen-induced fracture,the hydrogen induced lattice expansion strain was considered to study the additional contribution of different hydrogen concentration conditions to the stress of cable bolts.The results indicated that under the influence of stress-driven diffusion,as the hydrogen concentration increased,the stress value of hydrogen induced expansion gradually increased.Finally,the hydrogen-induced fracture damage variable of anchor cable material was defined to predict the occurrence of fracture.Meanwhile,combined with the scanning electron microscope section observation results,it was confirmed that hydrogen assisted stress corrosion cracking was the main fracture mechanism of prestressed anchor cable.This study simulated and predicted the diffusion and aggregation behavior of hydrogen content inside anchor cable materials under stress corrosion environment.At the same time,the effects of hydrogen diffusion and its influence on damage and failure fracture of anchor cable materials were considered from the perspective of hydrogen expansion strain.The obtained results provided a theoretical basis and research method for the control and prevention of corrosion damage instability of deep prestressed anchorage structures.